Glycine for Your Gains? Glycine Boosts Protein Synthesis (80%), Reduces Protein Degradation (-30%) in Muscle Cells

If glycine worked in athletes as it did in pigs or even isolated muscle cells, in which scientists recently observed a dose-dependent increase in protein synthesis (up to 80%) and reductions in protein degradation (-30%), it would be a go-to supplement for dieting athletes.

Glycine is not exactly the most popular amino acid supplement in the health and fitness community. With recent studies by a group of Chinese and American scientists from the State Key Laboratory of Animal Nutrition in China and the Texas A&M University, this may change - rightly so?

Only recently Wang et al. were able to show that dietary glycine supplementation enhances skeletal muscle growth in young pigs (Wang. 2014a,b) - an excellent model of human metabolism. In view of the fact that the mechanism has hitherto not been fully understood, it was difficult to judge whether the smallest possible amino, i.e. glycine, could / would be useful for trainees as well.

Learn more about amino acid supplements at the SuppVersity

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BCAAs deplete neurotransmitters

With their latest study, the same team of scientists, this time with KaiJi Sun as their lead author (Sun. 2016), provide an experimentally supported explanation of the anabolic effects of glycine - an explanation that is not just convincing but would also suggest that glycine could be an interesting supplement for bodybuilders and fitness freaks, as well as their grandparents.

Table 1: Physiological functions of glycine in animals and humans (Wang. 2013).

How's that? Well, while we are dealing with a cell line study, the scientists' analysis I'd like to remind all of you who are about to click on "comment" and complain that this is a follow-up study on the muscle-specific effects of an amino acid of which we have known for quite long that it is important for animal and human health.

Where's the human study in trained athletes? Early evidence for its ergogenic effects comes from Buchman, et al. (1999) who actually wanted to use glycine as a control for the beneficial effects of arginine on marathon runners, and then realized that it was glycine that enhanced the subjects' performance. Similar, albeit inconsistent effects have been reported for GPLC, i.e. Glycine Propionyl-L-Carnitine which improved resistance training performance in Jacobs, et al. 2009, but failed to yield ergogenic effects in a long-term follow-up with negative effects on aerobic acid with high dose (4.5g/day) supplementation of GPLC. Another glycine-compound with mixed evidence of its ergogenic prowess is GAKIC, i.e. glycine-arginine--ketoisocaproate, which has been shown to improve the performance of repeated cycling sprints in Buford, et al. (2004) - a result that could not be confirmed in a follow-up by Beis, et al. (2011), though.

Collagen hydrolysate, a high glycine protein (right bars), turned cata- into anabolism in a recent study in older women on low protein diets whey (left bars) did not (Hays. 2009).

At this point, the existing evidence is thus clearly insufficient to recommend glycine itself or any of the supplement industry's favorite glycine compounds as go-to supplements for athletes. The only thing that comes close is a recent study showing a decrease in nitrogen excretion (a marker of, you guessed it, protein breakdown) and thus reversal of the negative nitrogen balance with high glycine collagen protein - and by the way, the negative nitrogen balance persisted when the older women who participated in this 2-week study consumed a whey supplement (see figure on the left | Hays. 2009).

It is also an amino acid of which the previously cited studies showed that its use as a dietary supplement will (Wang. 2014b)...

• increased small-intestinal villus height (could reverse leaky gut and will improve nutrient transport), intestinal transport of glycine, plasma concentrations of glycine and GSH, as well as whole-body growth and protein accretion, while 
• reducing plasma concentrations of ammonia, urea, and glutamine, 

in a dose-dependent manner. Evidence the scientists rightly interpreted as follows: "Based on these lines of compelling evidence, we conclude that glycine is a nutritionally essential amino acid for maximal growth and development of milk-fed young pigs" (Wang. 2014b).

Figure 1: Effects of different doses of glycine on muscle anabolism (blue, left axes) and catabolism (gray, right axes) in C2C12 myotubes - all differences were highly significant (p = 0.001 | Sun. 2016).

With their latest study on C2C12 muscle cells, the scientists were now able to explain both the increased whole-body growth and protein accretion and the reduced ammonia, urea and glutamine concentrations, of which at least the former are clear signs of protein catabolism and thus potential muscle loss - actual gains, however, have yet to be observed outside of model organisms like pigs - also to quantify how much glycine it will take to achieve similar effects as they were observed in vivo.

MAFbx/atrogin-1 and MuRF1 gene activity mediates the degradation of protein and have an inhibitory effect on protein synthesis (Foletta. 2011).

Do I need glycine if I consume whey or BCAAs? With its ability to do both, promote mTOR and inhibit the MuRF1 and atrogin-1 gene expression and thus protein loss in C2C12 myoblasts, Glycine appears to have everything many people ascribe to BCAAs.

The one important difference, however, is that BCAAs don't affect the catabolic muscle genes and catabolism (learn more). While they appear to ameliorate the exercise-induced increase MuRF-1 total protein (Borgenvik. 2012), their effect on the gene expression of the atrophy regulators (see Figure on the right) in muscle cells is nowhere to be found.

Similarly, providing more protein in form of whey protein may further augment your protein synthesis via mTOR increases. What it does not do, however, is to affect the MuRF1 and atrogin-1 mRNA levels. Accordingly, it will only target one side of the net protein accretion equation (gains = existing muscle + muscle synthesis - muscle loss) - or as Stefanetti who studies this effect with different types of resistance exercise in 2014 write: "While WPH supplementation with ECC and CONC training further increased muscle hypertrophy, it did not have an additional effect on mRNA or protein levels of the targets [MAFbx/atrogin-1 and MuRF1] measured" (Stefanetti. 2014).

As discussed in the previous infobox, though, the one, decisive study that would proof practically relevant anti-catabolic effects glycine in healthy human beings, not isolated muscle cells, is not available yet. If you want to target muscle catabolism with supplements, carnitine (Keller. 2013) and HMB appear to be better, but likewise not fully proven candidates | Comment!

References:

• Borgenvik, Marcus, William Apró, and Eva Blomstrand. "Intake of branched-chain amino acids influences the levels of MAFbx mRNA and MuRF-1 total protein in resting and exercising human muscle." American Journal of Physiology-Endocrinology and Metabolism 302.5 (2012): E510-E521.
• Buchman, A. L., et al. "The effect of arginine or glycine supplementation on gastrointestinal function, muscle injury, serum amino acid concentrations and performance during a marathon run." International journal of sports medicine 20.05 (1999): 315-321.
• Buford, BRITNI N., and Alexander J. Koch. "Glycine-arginine--ketoisocaproic acid improves performance of repeated cycling sprints." Med Sci Sports Exerc 36 (2004): 583-587.
• Hays, Nicholas P., et al. "Effects of whey and fortified collagen hydrolysate protein supplements on nitrogen balance and body composition in older women." Journal of the American dietetic association 109.6 (2009): 1082-1087.
• Jacobs, Patrick L., et al. "Glycine propionyl-L-carnitine produces enhanced anaerobic work capacity with reduced lactate accumulation in resistance trained males." Journal of the International Society of Sports Nutrition 6.1 (2009): 1.
• Keller, Janine, et al. "Supplementation of carnitine leads to an activation of the IGF-1/PI3K/Akt signalling pathway and down regulates the E3 ligase MuRF1 in skeletal muscle of rats." Nutrition & metabolism 10.1 (2013): 1.
• Mascher, Henrik, et al. "Effects of essential amino acid supplementation on markers for anabolic and catabolic response to resistance exercise in female subjects." The FASEB Journal 24.1 Supplement (2010): lb278-lb278.
• Stefanetti, Renae J., et al. "Influence of divergent exercise contraction mode and whey protein supplementation on atrogin-1, MuRF1, and FOXO1/3A in human skeletal muscle." Journal of Applied Physiology 116.11 (2014): 1491-1502.
• Sun, KaiJi, et al. "Glycine Regulates Protein Turnover by Activating Akt/mTOR and by Inhibiting MuRF1 and Atrogin-1 Gene Expression in C2C12 Myoblasts." The Journal of Nutrition (2016): jn231266.
• Wang, Weiwei, et al. "Glycine metabolism in animals and humans: implications for nutrition and health." Amino acids 45.3 (2013): 463-477.
• Wang, Weiwei, et al. "Glycine stimulates protein synthesis and inhibits oxidative stress in pig small intestinal epithelial cells." The Journal of nutrition 144.10 (2014a): 1540-1548.
• Wang, Weiwei, et al. "Glycine is a nutritionally essential amino acid for maximal growth of milk-fed young pigs." Amino Acids 46.8 (2014b): 2037-2045.

Potassium: Your Heart and Vasculature Will Love it! Meta-Analyses Show: Supplements Work, but Ain't Necessary

Foods, not supplements should be your go-to potassium source.

You've read about the importance of adequate potassium intakes and the lack of potassium (esp. in relation to sodium, where only 10% of the US adults meet the Na:K ratio the WHO recommends to reduce your overall mortality risk) in our diets at the SuppVersity, before (read more about potassium deficits). You've also learned that potassium supplements can be necessary during very low-calorie diets where they prevent the paradoxical induction of insulin resistance (read more about potassium and insulin resistance).

What you haven't read yet, however, is the number Tang et al. put on the effect of supplemental potassium on vascular function in their recent review and meta-analysis in the International Journal of Cardiology (Tang. 2016).

Learn more about potassium (K) in previous SuppVersity articles:

Potassium vs. Diet-Inducded Insulin Resis.

In the Lime Light: The Ill Effects of Low K Intakes

Bad News: Most Americans are Sign. K Deficient

Lean, Healthy ... Correlates of High Hair Potassium

Eeating a High Protein Diet? Better Watch K!

Potassium Bicarbonate = Anabolic!?

The scientists conducted a literature search on the PubMed database and included all articles that were published before April, 2016. As indices of vascular function, the researchers selected...

• the pulse wave velocity (PWV), which has a strong correlation with cardiovascular events and all-cause mortality (7.9x increased CVD death risk in Blacher et al. 1999a; 5.4x increased all-cause mortality risk in Blacher et al. 1999b; see also Cruickshank, 2002 and Laurent, 2001)
• the augmentation index (AI), which is a sensitive marker of arterial status and predictor of adverse cardiovascular events in a variety of patient populations, where a higher augmentation index is associated with target organ damage (Shimizu. 2008), 
• the pulse pressure (PP), which is the difference between the systolic and diastolic pressure readings and has been found to be associated w/ a significantly increased risk of cardiovascular disease and CV mortality (e.g. +20% with every 10 mm Hg increase in pulse pressure in Blacher et al. 2000),
• the flow mediated dilatation (FMD), of which a recent meta-analysis of Matsuzawa et al. (2015) shows that each meager 1% increase in FMD translates in a 12% reduction in predicted cardiovascular events,
• the glycerol trinitrate responses (GTN), which can tell you how effectively your arteries can relax when that's indicated, and
• the level of intercellular cell adhesion molecule-1 (ICAM-1), which is a soluble adhesion molecule and prediction of coronary heart disease that is associated with increased CHD risk (e.g. +68% in Malik et al. 2001 comparing the highest to lowest tertiles)

Data from all seven randomized controlled studies (409 patients in total) were pooled as standardized mean difference (SMD) with 95% confidence intervals. The dosage of potassium that was used in the studies ranged from 40 to 150 mmol/day (1.6-6g/day). The duration of the interventions was between 6 days and 12 months.

Figure 1: Forest plots of studies testing the effects of potassium supplementation on arterial stiffness: A. Pulse wave velocity (PWV); B. Augmentation index (AI); and C. Pulse pressure (PP). The results revealed a significant improvement in PP (p=0.010), but no improvement in PWV (p=0.391) and AI (p=0.184 | typos corrected in figure from Tang. 2016)

The results of the meta-analysis show benefits for all parameters of arterial stiffness, but a statistically significant effect only for one, but an important parameter: the pulse pressure (PP; Figure 1.C). From previous meta-analyses, we know that the overall effect on people's heart rate is only modest (potassium doses of 0.9–4.7 g/d for 2–24 weeks changed heart rate by 0.2 bpm according to Gijbers et al. 2016).

Figure 2: Forest plots of studies testing the effects of potassium supplementation on blood pressure: A. Systolic blood pressure (SBP); and B. Diastolic blood pressure (DBP). The results indicated a significant improvement in SBP (p=0.044), but no improvement in DBP (p=0.122 | typos corrected in figure from Tang. 2016

The effects on the subjects' systolic blood pressure which was also assessed by Tang et al. (2016), on the other hand, is quite significant (see Figure 2) and a logical mechanistic consequence of the improved vascular elasticity. Benefits for ICAM-1 and FMD exist, but don't reach statistical significance due to significant inter-study differences (data not shown).

Overall, the experimental evidence in favor of potassium supplementation is scarce and the "wide variation of evidences make it difficult to make a definitive conclusion" (Tang. 2016). 

That's in contrast to the epidemiological evidence, by the way. The latter, which describes the effect of high and low dietary potassium intake clearly indicates that high(er) potassium intakes are associated with a reduced risk of stroke (-24% | Aburto. 2013; 20% | D'Elia. 2014), and curvilinearly associated reduced risk of incident cardiovascular and all-cause mortality (e.g. O'Donnell. 2014 | see Figure 3).

Figure 3: Curvilinear association between urinary potassium, a good marker of your potassium balance with higher values being indicative of high intakes, and (A) risk of cardiovascular and (B) all-cause mortality (O'Donell. 2014). 

I guess I could keep enumerating studies, here, but in conjunction with previous articles about the beneficial effects of potassium you should have learned enough about this deficiency mineral to be incentivized to double-check your dietary intake and resort to potasium citrate or bicarbonate (check out what potassium bicarbonate may be able to do for your gains | "11% Increase in Type I Fiber Cross Sectional Area During 12 Weeks of KHCO3 Supplementation) in case you're coming short.

Highly Suggested Read: "Common Nutrient Deficiencies, Their Health Consequences and How You Can Fix Them - Part 1: Potassium Deficiency, Bone & Protein Loss, Stroke, Heart Disease & High Mortality" | learn more

So you suggest supplementing with potassium? No, I don't. Eventually, I will always recommend foods over supplements. With potassium this is all the more true, because the average potassium rich food will also make a beneficial contribution to your overall dietary quality. I mean, look at the next best TOP 10 foods list for potassium on the internet: (1) Avocado. 1 whole: 1068 mg (30% DV), (2) Spinach. 1 cup: 839mg (24% DV), (3) sweet potato. 1 medium: 952 mg (27% DV), (4) coconut water. 1 cup 600 mg (17% DV), (5) kefir or yogurt. 1 cup: 579 mg (15% DV); (6) white beans. ½ cup: 502 mg (15% DV); (7) banana. 1 large: 422 mg (12% DV); (8) acorn squash; (9) dried apricots
½ cup: 755 mg (22% DV), and (10) mushrooms 1 cup: 428 mg (27% DV | DV = recommended daily intake value).

All of the previously listed foods belong to the category of foods to eat more of if you want to improve your health and physique - and yes, by implication, this means that you should resort to supplements (best forms are citrate and bicarbonate for the added beneficial anti-acidosis effect only if you cannot get your optimal potassium intake of 5-6g/day from foods | Comment!

References:

• Aburto, Nancy J., et al. "Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses." (2013): f1378.
• Blacher, Jacques, et al. "Aortic pulse wave velocity as a marker of cardiovascular risk in hypertensive patients." Hypertension 33.5 (1999a): 1111-1117.
• Blacher, Jacques, et al. "Impact of aortic stiffness on survival in end-stage renal disease." Circulation 99.18 (1999b): 2434-2439.
• Blacher, Jacques, et al. "Pulse pressure not mean pressure determines cardiovascular risk in older hypertensive patients." Archives of internal medicine 160.8 (2000): 1085-1089.
• Cruickshank, Kennedy, et al. "Aortic pulse-wave velocity and its relationship to mortality in diabetes and glucose intolerance an integrated index of vascular function?." Circulation 106.16 (2002): 2085-2090.
• D'Elia, Lanfranco, et al. "Potassium-rich diet and risk of stroke: updated meta-analysis." Nutrition, Metabolism and Cardiovascular Diseases 24.6 (2014): 585-587.
• Gijsbers, L., et al. "Potassium supplementation and heart rate: A meta-analysis of randomized controlled trials." Nutrition, Metabolism and Cardiovascular Diseases (2016).
• Laurent, Stéphane, et al. "Aortic stiffness is an independent predictor of all-cause and cardiovascular mortality in hypertensive patients." Hypertension 37.5 (2001): 1236-1241.
• Malik, Iqbal, et al. "Soluble adhesion molecules and prediction of coronary heart disease: a prospective study and meta-analysis." The Lancet 358.9286 (2001): 971-975.
• Matsuzawa, Yasushi, et al. "Prognostic Value of Flow‐Mediated Vasodilation in Brachial Artery and Fingertip Artery for Cardiovascular Events: A Systematic Review and Meta‐Analysis." Journal of the American Heart Association 4.11 (2015): e002270.
• Shimizu, Motohiro, and Kazuomi Kario. "Review: Role of the augmentation index in hypertension." Therapeutic advances in cardiovascular disease 2.1 (2008): 25-35.
• Tang, Xixiang, et al. "Effect of potassium supplementation on vascular function: A meta-analysis of randomized controlled trials." International Journal of Cardiology (2016).

Sweeteners in the Real World: 12% Increase in GLP-1 and Non-Significant Effects on Insulin W/ Diet Soda From Well-Known Brands and Seltzer + NNS Control - Implications?

Drinking diet soda now and then is certainly not going to harm you.

Everyone knows that "[n]on-nutritive sweeteners (NNS), especially in form of diet soda, have been linked to metabolic derangements (e.g. obesity and diabetes) in epidemiologic studies" (Sylvetsky. 2016). What only SuppVersity readers know is that experimental evidence to prove that the associations between obesity and artificial sweetener consumption from epidemiological studies is not the result of reverse causation, i.e. obese / overweight individuals gravitating towards the consumption of non-nutritively sweetened drinks in the false belief that this alone would help them to lose weight does not exist.

You can learn more about sweeteners at the SuppVersity

Aspartame & Your Microbiome - Not a Problem?

Will Artificial Sweeteners Spike Your Insulin?

Sweetened Drinks Beat Water as Dieting Aid

Chronic Sweeten-er Intake Won't Effect Microbiome

Sucralose Tricks 'Ur Energy Gauge - Implications?

Sweeteners In- crease Sweet- ness Threshold

Against that background, it is nice to see that a recent study by researchers from the NIH, the US National Institutes of Health in Bethesda, did something no previous study has done (which only proves that the currently available real = experimental science on artificial sweeteners is insufficient). In said study, the authors "aimed to test acute metabolic effects of NNS in isolation (water or seltzer) and in diet sodas" (Sylvetsky. 2016).

Table 1: Overview of the ingredients of the "real world" treatment with  Diet Rite Cola™ and Diet Mountain Dew™ - the ingredients I highlighted in yellow may be responsible for their ill effect on insulin (see bottom line).

To do just that, they conducted a four-period, cross-over study at the National Institutes of Health Clinical Center (Bethesda, Maryland). Over the course of the study, thirty healthy adults consumed 355 mL water with 0 mg, 68 mg, 170 mg, and 250 mg sucralose. So far that's nothing other researchers have not done already. What makes the study unique, though, is that the researchers also tested the effects of two different popular diet sodas (ingredients see Table 1) against an unflavored (only sweetened) seltzer control:

• 355 mL caffeine-free Diet Rite Cola™, Diet Mountain Dew™, which contained 68 mg sucralose and 41 mg acesulfame-potassium (Diet Rite) and 18 mg sucralose, 18 mg acesulfame-potassium and 57 mg aspartame (Mountain Dew), respectively 
• seltzer water with NNS (containing 68 mg sucralose and 41 mg acesulfame-potassium, equivalent to Diet Rite Cola™) 

The 355 ml test drinks were ingested in a randomized order, prior to an oral glucose tolerance tests. In addition to the blood glucose levels, the scientists tested, recorded and analyzed the "satiety hormone" GLP-1, the insulin response regulator GIP, as well as insulin itself and the levels of the insulin-controlling C-peptide for 130 min.

Figure 1: Serial data from OGTTs. Active (a) glucagon-like-peptide 1 (GLP-1) and (b) gastric inhibitory
peptide (GIP) response to the four different treatments (Sylvetsky. 2016)

In conjunction with the likewise measured glucose absorption rates, the rate of  gastric emptying, and the subjective hunger and satiety ratings of their subjects the scientists did thus generate an, as of now, unique dataset that shows:

• The diet sodas augment active GLP-1, while the sweetened seltzer has no effect on the GLP-1 response to the oral glucose test; with a sign. different between treatments (!)
• All four treatments left gastric emptying and satiety measures unaffected.
• All NNS treatments (Diet Rite, Mountain Dew and sweetened seltzer) increased the total amount of insulin that was produced after the oral glucose test, but this difference is (a) not statistically significant (p = 0.53; see Figure 3) and, more importantly, (b) so small that it is almost certainly physiological irrelevant - at least in the short run.
• None of the NNS treatments affected the subject's glucose levels significantly. 

Now the first thing that's interesting about these results is that the pre-study with water + sucralose showed no effect of the beverages on the insulin response - a result that implies that (a) the often-criticized sweetener sucralose has no effect on glucose metabolism (not news) and that (b) the observed albeit non-significant differences of the insulin response in the NNS vs. control trial must be due to another sweetener (check out Figure 2, differences in insulin occurred with all three NNS treatments, and not just with the sodas).

Figure 2: The acute glucose, insulin and C-peptide levels didn't differ significantly (p < 0.05)  at any point in the
130 minutes after the ingestion of the four test drinks (Sylvetsky. 2016).

The question is thus: What is it that messes with our insulin response in commercial diet sodas if it's not the allegedly bad sucralose, which has been acquitted in this and previous studies (more evidence I, II, III)? Well, since all three treatments had this effect and only Diet Mountain Dew™ contained aspartame, it's also not possible that the even more derided, yet likewise (metabolically) harmless aspartame of which previous studies even suggest that it lowers insulin - at least during workouts (aspartame's anti-insolinogenic effects) - is the culprit.

Figure 3: Glucose, GLP-1 and insulin AUC in the post-absorptive period (Sylvetsky. 2016); a statistically significant treatment effect was only observed for GLP-1 in the Diet Rite group (p < 0.05).

This leaves us with only one option to explain the (non-significant) difference between the test beverages' effects on insulin: acesulfame-K. The latter is not just a artificial sweetener that was present in all three non-nutritively sweetened (NSS) beverage, but also the only artificial sweetener of which studies indicate that it has insulinogenic effects (Liang. 1987a,b; Malaisse. 1998) - at low doses in vitro, and at higher doses in vivo. In fact, the...

Figure 4: Effect of acesulfame-K on insulin in rats.

"[...] effect of Acesulfame K on insulin secretion [see Figure 4] was similar to that observed by injecting or infusing [both right into the cervical vein and thus bypassing any potential effects of digestion and/or the interaction with sweet receptors in the gut] the same doses of glucose (150 mg/kg) body weight for injection and 20 mg/kg body weight/min for infusion), except that no hyperglycemia was observed with Acesulfame K (Loang. 1987)

In view of the exorbitant amount of acesulfame-K (human equivalent: 16mg/kg) Liang et al. (1987b) had to inject right into the bloodstream of their rats to induce significant in vivo effects on insulin, it appears more than questionable, though, if the oral ingestion 18mg and 41mg of acesulfame-K could, in fact, be responsible for the non-significant increase in insulin observed in the study at hand - and that's in spite of the more recent revelation that acesulfame-K has a disproportionately potent effect on the sweet taste receptors (Dotson. 2008).

So, if it's not a specific sweetener, what is it that triggers the differences - esp. in GLP-1?

Water or Diet Soda - What's the Better Diet Beverage? Study Confirms Fake Sweetness Promotes Weight & Waist Loss, Decreases Hunger, Blood Pressure, Cholesterol & Trigs | more

For insulin, the non-significantly different  response (as physiologically insignificant as it may be) could be triggered by a hitherto not fully understood interaction with sweet taste receptors during the sweetener preload that may influence the response to the subsequent oral glucose tolerance test.

The comparatively large, treatment effect on GLP-1, on the other hand, can't be ascribed solely to the interaction with sweet taste receptors. After all, there's a visible difference between the three NNS treatments, Diet Rite Cola™ (+12%), Diet Mountain Dew™ (+11%) and seltzer + NNS (+3%), with only Diet Rite Cola™ producing statistically significant and Diet Rite™ and Diet Mountain Dew™ potentially relevant increases of the incretin hormone GLP-1 (Waldrop. 2016).

The take-home messages from the study at hand are thus: (a) There's no physiologically relevant acute effect of any of the tested artificial sweeteners and/or their combination on insulin and/or the glycemic response to a standardized glucose load. (b) There's some evidence of a modulatory effect of soda on the GLP-1  response of healthy individuals. The latter may be triggered by either the "taste associated with diet soda" or, which is IMHO more likely, "the effect of other ingredients" (Sylvetsky. 2016). As far as other ingredients are concerned, any of the highlighted ingredients in Table 1 is a potential candidate. After all, both Diet Rite™ and Mountain Due™ produced a relevant increase in GLP-1 (~11-12%), while the otherwise additive-free seltzer with added sweeteners did not. Since none of them produced a measurable reduction in gastric emptying time and the rate of glucose absorption, both highly welcome side effects of the currently used GLP-1 drugs for diabetics (those increase GLP-1 10x more, though) the physiological relevance of the occasional Diet Rite™ or Mountain Dew™ diet soda or any other non-nutritively sweetened beverage is yet almost certainly zero.

Another Suggested Read: "If You Want to Lose Weight and Stave it Off, You'd Better Not Drink Water Instead of Artificially Sweetened Beverages" | read the full SuppVersity Article

This does not mean, however, that we can forget / ignore that the study at hand is an acute response study. So, in spite of the fact that (a) the acute effects on insulin are not statistically significant and (b) both the effects on insulin and GLP-1 are physiologically irrelevant if they occur once in a while. The downstream effect of the chronic ingestion of these or other diet sodas may be different. Accordingly, long-term studies to evaluate, whether the chronic ingestion of any of the sweeteners alone and/or in combination can produce potentially relevant health effects (positive or negative) are still warranted; and I say that even though I know and have written about the existing experimental (vs. epidemiological) evidence from human (not rodent) trials which shows that artificial sweeteners can promote body fat loss and maintenance - not the opposite | Comment!

References:

• Dotson, Cedrick D., et al. "Bitter taste receptors influence glucose homeostasis." PloS one 3.12 (2008): e3974.
• Liang, Yin, et al. "The effect of artificial sweetener on insulin secretionII. Stimulation of insulin release from isolated rat islets by Acesulfame K (in vitro experiments)." Hormone and metabolic research 19.07 (1987a): 285-289.
• Liang, Yin, et al. "The Effect of Artificial Sweetener on Insulin Secretion 1. The Effect of Acesulfame K on Insulin Secretion in the Rat (Studies In Vivo)." Hormone and metabolic research 19.06 (1987b): 233-238.
• Malaisse, Willy J., et al. "Effects of artificial sweeteners on insulin release and cationic fluxes in rat pancreatic islets." Cellular signaling 10.10 (1998): 727-733.
• Sylvetsky, et al. "Hormonal responses to non-nutritive sweeteners in water and diet soda." Nutrition & Metabolism 13:71 (2016).
• Waldrop, Greer, et al. "Incretin-based Therapy in Type 2 Diabetes: An Evidence Based Systematic Review and Meta-analysis." Journal of Diabetes and its Complications (2016).

Why's Maintaining 'Ur Fat Loss so F* Hard? Calorie Counter Will Ramp Up Your Appetite, No Matter What - Lifelong Anti-Weight-Gain Efforts Required in Formerly Obese Subjects

If  obesity is a chronic disease it cannot be surprising that it cannot be cured and weight loss maintenance requires life-long effort(s) on part of the formerly obese (note: things are different for non-obese individuals trying to shed extra-pounds).

I've discussed the issue of "metabolic damage" in a series of previous SuppVersity articles and pointed out that the scientific evidence supporting the disproportionate down-regulation of your metabolic rate with (significant) weight loss cannot support the exorbitant weight rebound we see in many so-called "weight-reduced individuals", who return to their "normal" dietary habits.

Now, a recent study from the US (Polidori. 2016) shows that this weight gain is mostly driven by a hitherto largely overlooked increase in appetite - an increase that goes way beyond any effects of "metabolic damage".

High protein helps, but do not counter the weight loss induced changes in RMR & appetite

Are You Protein Wheysting?

5x More Than the FDA Allows!

More Protein ≠ More Satiety

Protein Oxidation = Health Threat

Protein Timing DOES Matter!

More Protein = More Liver Fat?

Before we get into a discussion of the implications of this research, though, I would like to briefly summarize what Polidori et al. did to arrive at their important conclusion that...

"feedback control of energy intake plays an even larger role [than energy expenditure adaptations when it comes to the post-diet jojo-effect] and helps explain why long-term maintenance of a reduced body weight is so difficult" (Polidori. 2016)

Using a validated mathematical method the authors calculated the energy intake changes of 153 patients who lost a significant amount of weight over the course of a 52-week placebo-controlled trial with canagliflozin, a sodium glucose co-transporter inhibitor, a commonly used diabesity drug that increases urinary glucose excretion.

Association between adaptive thermogenesis and weight loss in 151 overweight patients from three studies after dietary or bariatric surgery-induced weight loss.

"Metabolic damage" does not scale with weight loss: While it would be logical to assume that there was a linear increase in "metabolic damage", i.e. the reduction of your resting metabolic rate, in response to each pound of body weight you've lost. The existing evidence, which has recently been reviewed by Müller et al. (2016), however, suggests that this link does not exist (see Figure on the left). This is also in line with the results of the study at hand and previous studies which didn't find an effect of increasing weight loss on the subjects' appetite (this is discussed in detail below).

In spite of the fact that we are talking about experimental evidence, the scientists still had to rely on math / statistics to come up with data on the actual energy intake of their subjects.

Metabolic damage in Biggest Losers | more

"We calculated the free-living energy intake changes in 153 patients treated with 300 mg/day canagliflozin over a 52-week trial using the mea-sured body weight data and an assumed mean UGE [urinary glucose excretion] of 90 g/day as inputs to a mathematical model that has recently been validated against an expensive biomarker method" (Polidori. 2016 | note: it is still debatable how accu-rate this calculation is as it depends on a relatively simple formula that uses a bunch of input parame-ters based on theoretical assumptions).

Now, this use of a sodium glucose co-transporter inhibitor and the resulting urinary loss of approximately 90 g of glucose per day (that's 360 kcal/day) is an important qualifier here, as it is a way of creating an energy deficit of which the scientists argue based on previous scientific evidence that the way the scientists induced an energy deficit ...

• does not alter the subjects' energy expenditure (regular dieting would acutely decrease their metabolic rate) or central pathways controlling energy intake (hunger & appetite) and 
• allows for weight loss even though the patients are not directly aware of being in an energy deficit - or, put more simply, without any 'dieting efforts' or austerity

As Polidori et al. point out, any observed increased energy intake countering the weight loss induced by SGLT2 inhibition therefore likely reflects the activity of the feedback control system - your body's very own 'calorie counter' as I have called it in the headline.

Learning from those who did it: Wyatt et al. used data from the National Weight Control Registry (Wyatt. 2005) to follow a still barren path in obesity research: studying what those who manage to lose weight and keep it off did right. Until now, way too much effort is spend on identifying diet mistakes; mistakes that would be automatically avoided if you did the right things. Unfortunately, there's no magic bullet or, as the authors say: "If weight loss maintenance requires “swimming upstream” against the environment, then these are the best swimmers" (Wyatt. 2016).

The use of refeeds was not part of Wyatt's research interest, but there's experimental evidence that refeeding twice a week promotes fat loss | more.

What Wyatt et al. were able to show, however, is that people who have successfully maintained weight loss share similarities in how they keep weight off. And here's what they did: (1) They didn't rely on dieting, only, but have increased their total physical activity (to 3,293 kcal per week) as well (only 9% of those who kept the weight off did it with dieting, only); (2) they didn't stop dieting / return to their old habits after losing a certain amount of weight, but maintained a tightly energy controlled diet; (3) they constantly monitored their weight and intervened when they saw weight gain of more than 3-5 pounds; (4) cheri-shing improvements in quality of life and self-confidence.

Aspects I wouldn't include in the list, yet, are: consuming a low fat diet (that was probably due to the popularity of low fat back in the day), eating breakfast everyday (there simply is no convincing evidence that this will mechanistically promote weight loss and maintenance), and improve.

Beware: Chronic dieting at low deficit can make you fat | more!

It is also noteworthy that the study at hand provides additional evidence of the mechanisms which are driving the post-dieting weight regain (i.e. an increase in appetite and thus usually food intake) - a mechanism that is weight and not deficit dependent. This, in turn, may be considered further evidence of the existence of something many people call a "set point" (i.e. a given weight at which your body is "happy" and your appetite will match your energy requirements pretty well). Unfortunately, Polidori, et al. cannot explain why the weight-controlling appetite increase does not scale with the amount of weight the subjects lost. Why's that important? Well, if you lose 10kg or 20kg, your appetite will increase to the same extent. If we assume that this increase in appetite translates directly into increases in food intake, the rate of weight gain will be the same - regardless of whether you lose 10kg or 20kg of body weight - it's the total amount that counts.

Is it futile to even try to lose weight? An excellent comment by Priya Sumithran & Joseph Proietto says NO - (1) Modest (5–10 %) weight loss confers significant reductions in the risks of several weight-related conditions such as type 2 diabetes, obstructive sleep apnoea and non- alcoholic fatty liver disease [18], and is likely to be accompanied by milder metabolic adaptation | (2) Although the majority of people will eventually regain much of the lost weight, results are variable, and a proportion of people manage to maintain clinically beneficial weight loss even in the long-term: more than 4000 U.S. adults in the National Weight Control Registry database (97 % Caucasian, 80 % women), for example, have maintained a loss of at least 13.6 kg (30 lbs) for a mean of over 5 years |  (3) New pharmacological therapies that help weight loss and maintenance are becoming available (e.g. GLP-1 agonists) and other drugs that mimic the effects of RYGB surgery are in the development pipeline. And still, while there's hope, it's important to acknowledge that "[l]ike other chronic con-ditions, obesity is not cured after the phase of treatment (weight loss), and strategies for long-term management (maintenance of weight loss) are required " (Sumithran. 2016).

So does the study just confirm that people who have gotten fat once are doomed forever? That's difficult to tell, after all, some interventions such as RYGB weight loss surgery appear to have a decent rate of success. While the subjects may not turn into fitness models, many manage to maintain a decently healthy weight after crash-dieting down to a normal BMI-range.

Surgery may yet not be the only option. After all, there's reason to believe that there's a threshold level of weight loss after which the previously discussed compensation effects occur. It may thus well be possible that small weight changes are uncompensated by changes in energy intake. If we consider the previously referred to concept of a weight set-point to be dynamic in both directions, it is thus not impossible that losing your weight in baby-steps with adequate periods at an energy equilibrium (calories in = calories out) and no further weight loss in-between the short dieting periods may help you to lower your set-point and achieve (in the long-run) meaningful weight-loss without compensatory increases in appetite that will get you back to your original weight in no time | Comment on Facebook!

References:

• Müller, Manfred J., Janna Enderle, and Anja Bosy-Westphal. "Changes in Energy Expenditure with Weight Gain and Weight Loss in Humans." Current Obesity Reports 5.4 (2016): 413-423.
• Polidori, David, et al. "How strongly does appetite counter weight loss? Quantification of the feedback control of human energy intake." Obesity 24.11 (2016): 2289-2295.
• Sumithran, Priya, and Joseph Proietto. "Maintaining weight loss: an ongoing challenge." Current Obesity Reports 5.4 (2016): 383-385.
• Wyatt, Holly R., et al. "Lessons from patients who have successfully maintained weight loss." Obssity Management 1.2 (2005): 56-61.

In Pro O-Lifters, Pomegranate Juice Boosts Training Volume + Max. Weight, Reduces DOMS, RPE, as Well as Markers of Muscle Damage + CNS Stress and Speeds Up 48h Recovery

Regular POMj did the ergogenic trick.

Pomegranate is one out of a dozen of purported "superfoods" that actually has research backing up its efficacy. With the publication of a recent study by scientists from the University of Sfax and the Otto-von-Guericke-University Magdeburg in Germany (Ammar. 2016).

What makes the study at hand more interesting than most of the previously published studies is that the authors investigated the effect of natural Pomegranate juice supplementation on performance and acute and delayed responses of muscle soreness and biomarkers of muscle damage not in response to endurance training, but rather in response to a weightlifting training session.

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For their study, Ammar et al. recruited 9 elite weightlifters [age: 21 ± 0.5 years, body mass: 80 ± 9.5 kg, height 175 ± 8.1 cm (mean ± SD)]. The inclusion criteria were:

• subjects trained at least five sessions per week (between 15h:30 and 17h:30) with 90 to 120 min per session,
• subjects had an experience of more than 3 years in Olympic weightlifting and 
• subjects didn’t have any injuries and they didn’t use any antioxidant (e.g., vitamin E, A, C etc.) or anti-inflammatory drugs during the experimental period and one month before. 

As you can see in Figure 1 the study used only two acute (+ follow up) response tests in form of Olympic-Weightlifting-sessions after either placebo (PLA) or natural pomegranate juice (POMj) supplementation.

Figure 1: Experimental design. NB: the pre-sessions 1 and 2 values correspond to values of 48-h recovery; Weightlifting performance was calculated during both test sessions; Acute (RPE) and delayed (DOMS) perceived muscle fatigue and soreness were assessed respectively 3min and 48 after both test sessions (Ammar. 2016).

After an initial 1-RM strength test, the subjects performed their habitual training programs (training session includes three Olympic-Weightlifting exercises: snatch, clean and jerk, and squat) on two separate days (3 weeks apart) while using either a placebo (PLA) and/or a pomegranate juice (POMj) supplement in the 48h recovery period:

"Supplements (1500 ml) of PLA or POMj were taken three times daily in the 48h that proceeded respectively these two training sessions (i.e. 250ml × 6 times with 8-h intervals between it). Moreover, 1h before the training sessions, participants consumed an additional 500 ml of PLA and 500 ml of POMj, respectively" (Amman. 2016).

To assess the recovery kinetic of the biological parameters, blood sample, temperature, HR and SBP were collected at resting state (i.e., after 10 days of recovery, blood sample 6) and before, immediately (3min) and 48h after the training session.

In their 2014 study, Machin et al. saw no benefit of doubling the dose of pomegranate juice concentrate and thus the antioxidant load (from 650 mg GAE/d to 1300 mg GAE/d).

A note on POMj dosing: Unfortunately, the full text contains contradictory information on the total dosage, but after reading the respective paragraphs thrice, I believe that the 1250ml that are also mentioned in the FT were consumed only on the workout day, with 500ml "extra" being consumed right before the workout. That's quite a significant amount of pomegranate juice and not cheap - at least if-if you are contemplating using it year-round (I guess I don't have to tell you that it would also be necessary to confirm that this was an effective strategy).

And if we are already talking about dosing, it may be worth mention that Machin et al. didn't find a dose-response effect in their 2014 study, even when they doubled the amount of pomegranate juice concentrate they administered to their subjects before muscle damaging exercise the muscle soreness was not further reduced and the recovery of muscle strength was not accelerate beyond what the lower dose supplmentation regimen achieved (see Figure on the left).

In conjunction with heart rate and blood pressure data, as well as the recorded weightlifting performance, RPE, and DOMS the blood samples which were analyzed for hematological parameters, muscle damage and C-reactive protein (CRP) served as markers of post-exercise recovery with or without 3x250 ml of natural pomegranate juice:

"The tested quantity of the natural POMj was prepared from a fresh pomegranate fruit 48h before the beginning of the experimentation and was frozen and stored at -4°C. No additional chemical products were added to the natural POMj. Each 500-mL of the tested POMj contained 2.56g of total polyphenol, 1.08g of orthodiphenols, 292.59mg of flavonoids and 46.75mg of flavonols" (Ammar. 2016).

The PLA juice was a pomegranate-flavored commercial drink contained water, citric acid, natural flavor and natural identical flavor (Pomegranate), sweeteners (aspartame × (0.3g/l), acesulfame K (0.16g/l)), stabilizers (Arabic gum) and didn’t contain antioxidants, vitamins nor polyphenols.

Figure 2: Calculated performances with PLA and natural POMj supplementations.
*:Significant differences between PLA and POMj conditions (Ammar. 2016).

As you can see in Figure 2, the pomegranate supplement didn't just produce the desired recovery effects, it also increased the the subjects' physical performance (i.e., the total lifted amount and maximally lifted amount) compared to placebo treatment. Furthermore, the scientists' statistical analysis of the data showed a significant POMj supplementation effect (Figure 2 & 3)...

• on both performances variables during POMj condition compared to PLA (+8.29±3.8% and +3.26±0.83%, respectively for the total and the maximally lifted amounts), as well as 
• on RPE and DOMS which were significantly reduced by -4.37±1.45% for RPE and -13.4±3.84% for the knee extensors’ DOMS in the POMj condition.

So, acutely, there were significant benefits of consuming 3x250ml of regular pomegranate juice and an extra 500ml pre-workout.

Figure 3: Deep onset muscle soreness and rate of perceived exertion (Ammar. 2016).

Likewise acute were an augmented increase in the subjects' core temperature (+0.42%) and a lower rate of increase in heart rate (HR) and systolic blood pressure (SBP | -4.46% and -1.81%) the scientists observed in the POMj condition, as well as 20% and 15% reduced creatine kinase and LDH levels (both indicative of reduced muscle damage).

After 48h the improvements in blood pressure and heart rate (indicative of faster recovery of the central nervous system) as well as the reduction in CK and LDH persisted. In addition, the scientists recorded lower levels of the liver enzyme AST, which is likewise an indicator of reduced muscle damage (learn more about AST).

Many other purported superfoods such as walnuts, cacao, and beans, may fail the reality test | learn more.

So what? The ingestion of 3x250ml (+500ml on workout days) of regular (natural) pomegranate juice didn't just improve the 48h exercise-recovery it also reduced the subjects' muscle soreness, their feeling of exertion and that at concomitantly improving performance markers. Even though you could thus argue that their workouts were more intense, the improvements in subjective markers of muscle damage were in line with likewise significant improvements of CK and LDH, which indicate that the subjects muscles were indeed protected from damage during snatching, the clean and jerk, and squatting.

With additional evidence of a less pronounced impact on the central nervous system, and back-up from previous studies by Trombold et al. who found reduced  muscle damage and a faster recovery of arm strength after eccentric exercise in their 2011 study pomegranate juice may in fact be an interesting supplement for resistance training (and probably other) athletes | Comment!

 References:

• Ammar, Achraf, et al. "Pomegranate Supplementation Accelerates Recovery of Muscle Damage and Soreness and Inflammatory Markers after a Weightlifting Training Session." PloS one 11.10 (2016): e0160305.
• Machin, Daniel R., et al. "Effects of differing dosages of pomegranate juice supplementation after eccentric exercise." Physiology Journal 2014 (2014).
• Trombold, Justin R., et al. "Ellagitannin consumption improves strength recovery 2–3 d after eccentric exercise." Med Sci Sports Exerc 42.3 (2010): 493-8.
• Trombold, Justin R., et al. "The effect of pomegranate juice supplementation on strength and soreness after eccentric exercise." The Journal of Strength & Conditioning Research 25.7 (2011): 1782-1788.