Monday, July 22, 2013

The Satiating Truth About Proteins and Why High Protein and Low Amounts of Low GI Carbs Don't Mix Well

So can you? I mean, can you really get rid of hunger pangs by upping the protein content of your meals? Yes, you can, but as usual, there is a string attached, here. One of the infamous "on the other hands", as Carl Lanore likes to call them.
Despite the fact that I actually have to stop some of you from eating too much protein [I am not talking about ill health effects, but a saturation effect for the benefits with 2-3x the RDA, here; cf. "1.6-2.4g/kg Protein Turn Short Term Weight Loss Intervention into a Fat Loss Diet" | read more ], the obese majority of the inhabitants of the Western Obesity belt would certainly benefit from a couple of extra grams of protein in their diets.

One of the reasons protein can help you get and stay lean relates to its profound satiety effects; effects, which have recently been reviewed by a group of researchers from the State Key Laboratory of Cardiovascular Disease at the Fuwai Hospital in Beijing, China (Yang. 2013)

Higher satiety, lower glucose and ghrelin spikes...

... these are the most significant observations the scientists made, when the surveyed the PubMed, Cochrane library, EMBASE, and HighWire Press data bases to identify randomized, crossover trials that investigated the acute effects of isocalorically prescribed high versus normal protein test meals on satiety and ghrelin. Starting out with a total of 1,858 potentially relevant articles the scientists narrowed their selection down to 123 by removing duplicates and studies that did look like they would qualify, but turned out to be off-topic upon closer scrutiny. Of those 123 they eventually dropped another 103 articles based on detailed evaluation, including inadequate data, lack of NP groups, ghrelin administration related study, long-term HP diets and others. That left Yang et al. with 20 studies in total and a couple of interesting results.

Figure 1: Satiety effects (left) and corresponding decreases in the ghrelin AUC in the subjects of the studies under scrutiny in response to high vs. normal protein meals (Yang. 2013)
As you can see in figure 1 the effect size may differ, but with the exception of the 2011 study by Makris et al. the effects were highly beneficial. So what was it about the Makris study that could explain the difference? Well let's see... what are we talking about here? Was there something "wrong" with the breakfast (= test meal)? It consisted of a small scrambled egg and oatmeal prepared with butter and water, sweetened with sugar, and topped with slices of fruit. In order to achieve a lower GI, ...
"[o]ld Wessex instant oatmeal, dextrose, and slices of a semi-ripe banana were used for the high GI meals. McCann’s steel cut oatmeal, fructose, and slices of a Granny Smith apple were used for the low GI breakfasts." (Markris. 2011)
And to get the protein up in the HP conditions, casein powder was added to the scrambled eggs and oatmeal in the high protein condition to increase the protein content from ~14% to 28% of total energy. I see nothing wrong, here, and the same goes for the macronutrient profiles (see table 1).
Table 1: Nutrient content of breakfast meals and amount of water served with the meal (Makris. 2011)
Basically, we have a ~1/2 ratio of protein in the normal vs. high protein arm of a study comparing LGI/normal, HGI/normal to LGI/high and HGI/high protein meals and if we take a close look at the individual results it turns out that no high protein per se, but rather the glorified combination of high protein + low GI carbohydrates appears to be the underlying problem here.

The combination of low GI foods and high protein can make you ravenous

I know it sounds impossible, but in the end, it's logic. Spiking insulin (>50% more insulin in the high protein + low GI vs. the normal protein + low GI arm of the study) in the absence of glucose will make you freakin' hungry (and yes, casein is almost as insulinogenic as whey, learn more). For the subjects in the Makris study this effect was so pronounced that the subjects in the low GI + high protein arm of the study ate ~1800kcal while those in the low GI + normal protein arm consumed only ~430kcal on the subsequent lunch...
Figure 2: Energy intake during lunch after breakfast with high/low GI carbs & high/low amounts of protein (Makris. 2011) the way, did I mention that the high GI + high protein arm displayed the greatest practically relevant satiety effect with a caloric intake of only ~1,300kcal during lunch? I did not? Well it would have been in figure 2, anyway.

High or low GI, carbs in the morning or in the evening, cookies and dingdongs or all bran. Many questions and too many questionable answers from studies on rodents or diabetics and questionable nutrition experts all around the web .. So what are Mr. and Mrs. Healthy-And-Athletic-Average-Joe supposed to do low GI, low carb, low [...] ? (learn more)
Bottom line: The synergy of high protein, high GI carbs in terms of practically relevant increases in satiety that was observed of all things in the study by Makris et al. the only one with an "on average" negative effect of high protein intakes on satiety in the meta-analysis by Yang et al., may in fact be the reason why simply upping your protein intake has proven time and again to help sugar addicted overweight individuals to shed weight and body fat. After all, they are the ones who live on high GI carbs, anyways.

That being said, the 30g/per meal strategy still is an appropriate and simple nutritional strategy both lean and overweight people can benefit from. Larger amounts of low GI carbs, a non-insulingenic protein source, like steak, or a simple mixture of fast and slow carbs all may solve or at least ameliorate the "hunger problem" and help you to lose body fat, stay lean, build muscle and maintaining muscle mass on a diet (see "Protein Timing Reloaded" | learn more).

  • Makris AP, Borradaile KE, Oliver TL, Cassim NG, Rosenbaum DL, Boden GH, Homko CJ, Foster GD. The individual and combined effects of glycemic index and protein on glycemic response, hunger, and energy intake. Obesity (Silver Spring). 2011 Dec;19(12):2365-73. 
  • Yang D, Liu Z, Yang H, Jue Y. Acute effects of high-protein versus normal-protein isocaloric meals on satiety and ghrelin. Eur J Nutr. 2013 Jul 4.