Evidence From the Metabolic Ward: 1.6-2.4g/kg Protein Turn Short Term Weight Loss Intervention into a Fat Loss Diet

2x-3x higher than RDA protein intakes work equally well for men and women, to get and stay lean and lose fat and build / maintain muscle.
There are very few principles I believe are set in stone and valid regardless of your age (maybe not for toddlers), your training goals and your nutritional "orientation" (paleo, low carber, low fat eater, or whatever), and among these the "Have at least 30g of quality protein (eggs, meats, dairy, fish, etc.) with every major meal" (this assumes you eat 3meals+ per day) probably is king. It is the recipe to success and I actually don't feel as if it was necessary to convince you of the advantages this high(er) protein intake will have on your physique and - although the medical establishment is still reluctant to admit that - your health, as well. Still, the most recent study from the Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine in Natick, Massachusetts, USA; have much more to offer than "just" some additional evidence to the superiority of high(er) protein diets on a cut.

It's more than high time to revise the RDA

The study was designed to assess the effects of different dietary protein (RDA = 0.8g/kg, 2x RDA = 1.6g/ kg and 3x RDA =2.4g/kg) intake on body composition and postabsorptive and postprandial muscle protein synthesis on a 21-day cut (-30% energy restriction phase; ED). The latter was preceded by a 10-day weight maintenance (WM) period.

To up the calculated energy deficit to 40% the physically active (physical activity 3– 4 d/wk), weight stable ( 2 kg; for a minimum of 2 mo before the study), 39 volunteers [32 men (11 military, 21 civilians) and 7 women (7 civilians)] with a body mass index (BMI) between 22 and 29 kg/m² and a sufficient baseline fitness had to exercise daily:
"You told me to eat more protein and this burger has both meat and cheese!" - This and other mishaps are the rule, not the exception in uncontrolled dietary interventions (learn more). The fact that the study at hand took place in the metabolic ward of the U.S. Department of Agriculture Grand Forks Human Nutrition Research Center really is a HUGE PLUS.
"To isolate the effects of the diet and minimize the potential of an exercise training stimulus, physical activity during WM was prescribed at levels comparable to those reported in prestudy 7-d physical activity records. Volunteers performed low-tomoderate-intensity (40 – 60%Vo2peak) treadmill and cycle ergometry steady-state physical activity sessions daily. Intensity was based on pre-study Vo2peak
measurements obtained during a progressive intensity treadmill test and verified during
familiarization trials using indirect calorimetry (ParvoMedics) and corresponding heart rate. Workloads during steadystate physical activity sessions were adjusted accordingly to
ensure accuracy using the heart rate reserve method and portable heart rate monitors." (Pasiakos. 2013; my emphasis)
The study took place in the metabolic ward (so there was no cheating involved here => HUGE PLUS; cf. ) at the U.S. Department of Agriculture Grand Forks Human Nutrition Research Center. All volunteers were required to abstain from nutritional supplements, alcohol, smoking, and all medications, unless acetaminophen-containing products were provided by the investigator or study physician. Volunteers were also required to be in their assigned rooms with lights out by 11 P.M. (possibly very important; learn why) to ensure adequate and similar levels of sleep.

Don't worry this was not "cardio only"

To maintain prestudy muscular fitness levels, the volunteers also performed resistive-type physical activity 3d/wk. However, "to minimize the potential of an unaccustomed, anabolic stimulus influencing study outcome measures, the intensity and volume of the resistive-type exercise was low" (Pasiakos. 2013):
Table 1: Energy / macronutrient content of the diets (updated on June 21; previously there was a copy + paste error in the table)
"Specifically, volunteers performed one single-joint movement per major muscle group (3 sets of 15 repetitions) using workloads determined during the prestudy period. Frequency, intensity, mode, and volume of resistive-type activities did not change during the 31-d study. Research staff who were blinded from dietary assignment supervised all physical activity sessions for safety and accuracy". (Pasiakos. 2013)
The body weight, was recorded in two day intervals and the body composition was quantified using a  dual-energy X-ray absorptiometry (DXA) during WM (day 9) and ED (day 30). To elicit the underlying mechanisms, the resting metabolic rate, protein synthesis, nitrogen balance and the expression of intracellular signaling proteins were tested, as well.
Figure 1: Change in body composition and protein synthesis (Pasiakos. 2013)
As you can see in figure 1, there was a baseline and dose-dependent effect on the changes it total weight and body composition, respectively.
Body weight during WM was similar between dietary treatment groups and remained stable from d 1 (group mean, 77.5 1 +/-5 kg) through d 10 (77.1 1 +/-5 kg). Overall, volunteers lost 3.2 0 +/- 2 kg during the 21-d ED; 3.5 0 kg for RDA, 2.7 0 kg for 2 -RDA, and 3.3 0 kg for 3 -RDA (P < 0.05). Independent of dietary protein, percentage body fat decreased (P < 0.05) from 19.8 1% during WM to 18.1 1% during ED, and the change in percentage body fat was similar between RDA (1.3 0 +/- 3%), 2 -RDA (1.8 0 +/- 4%), and 3 -RDA (1.9 0 +/- 3%)." (Pasiakos. 2013)
What's worth taking a closer look at, is yet the proportion of total weight loss due to changes in fat mass (FM) and FFM, which differed across dietary protein levels.
  • the percentage of total weight loss attributed to reductions in fat mass (FM) was higher (P < 0.05) for 2 -RDA (70.1 7%; 1.9 0 +/- 3 kg) and 3 -RDA (63.6 5%; 1.9 0 +/- 2 kg) than for RDA (41.8 5%; 1.6 0+/-2 kg)
  • the percentage of total weight loss due to a loss of fat free mass (FFM) was lower for 2 -RDA (29.8 7%; 0.8 0 +/- 2 kg) and 3 -RDA (36.4 5%; 1.2 0. +/- 3 kg) as compared to RDA (58.2 5%; 2.3 0 +/- 3 kg)
  • the fat to lean mass loss ratio was 30% higher in the medium protein intake group, in other words, the increase in protein intake in the 3xRDA group did not protect the lean mass any better than the 1.6g/kg in the 2xRDA group
While the latter change did not reach statistical significance, the trend is clear and I suspect with a higher number of participants, the scientists would have been able to show that the 3x RDA intake is not just worthless, but actually contra-productive, if your goal is stable ongoing fat loss.

No inter-group differences in the majority of signaling proteins

All the changes took place in the absence of statistically significant inter-group differences in the changes in anabolic intracellular signaling and gene expression [ignore the following list if you are no geek ;-], i.e.
  • postprandial Akt (Ser 473) phosphorylation was increased 1.4-fold higher (P < 0.05) compared to postabsorptive levels
  • postprandial p70 S6K1 (Thr 389), eIF4E Ser (209), and rpS6 (Ser 235/236) phosphorylation status was 16, 1.9, and 15.5-fold higher (P < 0.05), respectively, compared to postabsorptive phosphorylation levels
  • phosphorylation status of eEF2 (Thr 56) was lower (P < 0.05) after feeding
The more important general observation was yet that the upregulation of these signals 3 h after consuming a protein-containing meal, demonstrated a main feeding effect for all proteins of interest (P < 0.05). On the other hand, their expression was not influenced by energy status or the level of dietary protein intake (and let's be honest, what would an increase be worth if the data in figure 1 already told us what the real-world implications are?)
Figure 2: Changes in postabsorptive muscle protein synthesis-associated mRNA expression levels during the diet phase (-40% energy intake) of the study (Pasiakos. 2013)
Additionally, the energy deficit increased the mRNA expressions of a couple of other proteins implicated in the intracellular regulation of muscle protein synthesis:
"Transcription of Vps34, a protein involved in amino acid sensing and amino acid-mediated stimulation of mammalian target of rapamycin (mTORC1) signaling, was 1.2-fold higher (P < 0.05), while expression of mTORC1 inhibitors REDD1 and REDD2 were both 1.3-fold higher (P < 0.05) after ED compared to WM. Increasing dietary protein intake increased Vps34 mRNA expression, with 1.2-fold higher levels for 3x-RDA than RDA (P 0.05). MAP4K3, LAT1, and SNAT2 mRNA levels were not influenced by energy and dietary protein manipulations." (Pasiakos. 2013)
In view f the slight advantage of the 3xRDA diet in terms of the stimulation of protein synthesis, you may want to come back to the statistical insignificance of the superiority of the 2xRDA diet to keep indulging the same hilarious amounts of protein that have probably not gotten yourself anywhere near contest shape in the past, well, let's take a look on a couple of other observations, then:
  • While the nitrogen balance remained negative (meaning the body was burning more protein than it stored) over the whole trial in the 0.8g/kg group, it returned to baseline (weight maintenance levels) first in the 1.6g/kg (=2x RDA) group (day 17!). This restoration of to pre-diet levels was observed only on day 30 in the high protein group (2.4g/kg) and the that without any significant advantage of the 3xRDA over the 2xRDA intake (if anything it was lower in the high protein group; see figure 3)
  • There was no "thermogenic advantage" - or whatever people usually like to call the purported beneficial effect that comes with the ingestion of higher amounts of protein; in fact, the resting metabolic rate was identical for all three groups over the whole 21-day diet period. 
  • With a diet that was high in carbohydrates and low in fat (see table 1), the conversion of protein to glucose, was likely relatively limited and the potential downsides of high protein + low carb diets, where most of the protein will be broken down in the liver to supply your body with glucose and any temporary increase in insulin due to fast acting protein sources were not an issue.
In the end, the increase in postprandial protein synthesis in the 3x RDA group is therefore worthless, because it went hand in hand with an increase in wastefulness due to which the absolute protein retention did not differ all that much and the differences in lean mass loss 0.1kg) are clearly insigificant- plus: If you simply do the math, the ratio of fat free to fat mass loss, is still 31% higher in the 2x RDA group.

Irrespective of how many supplements you take - you cannot out-supplement a bad diet, laziness and a lack of motivation & determination. Still, especially for the elderly HMB with it's pronounced anti-cababolic effec could help - particularly on a diet (learn more; leucine vs. HMB)
So what's the optimum then? If we reconcile the results of the study at hand, the "optimal" protein intake would thus probably be somewhere between 1.6g/kg and 2.0g/kg an thus in the <200g range for the vast majority of people. If you also consider that this value includes all protein even that from rice, and other "non-quality" protein sources, the study at hand does not confute my previous recommendation to stick to a 1.5g/kg-2.0g/kg (per total body mass) protein intake from quality protein sources, to discount the additional protein you will be getting from "low protein food" (too much counting will only make you neurotic) and to do that irrespective of whether you are bulking and or dieting  .

One thing you may want to keep in mind though, is the fact that the overall calorie deficit of ~40% may still have been a little to high - it was not enough to elicit a significant reduction in the resting metabolic rate, but still enough to induce a loss of at least 30% of lean mass. A lower caloric deficit 20-30%, a little more patience and a focus on hypertrophy-specific weight lifting are thus probably a way more significant difference, than whether you consume 1.6g/kg or 2.4g/kg body weight.

  • Pasiakos SM, Cao JJ, Margolis LM, Sauter ER, Whigham LD, McClung JP, Rood JC, Carbone JW, Combs GF Jr, Young AJ. Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial. FASEB J. 2013 Jun 5. [Epub ahead of print]
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