By Daniel Gwartney, M.D.

Observing the trends in science and marketing in the sports nutrition and “weight loss” categories is a lot like watching sports nowadays. You have teams competing against each other (e.g., low-fat versus low-carb; paleo versus vegan; intermittent fasting versus grazing), commentators voicing their opinions (e.g., medical journals), spectators voicing their opinions (website message boards), sponsors tagging along for celebrity endorsement (e.g., the Dr. Oz effect) and players who are pretty much just expendable meat (the 15% of people actually doing anything productive for themselves). A multibillion-dollar industry, much like sports viewing, everything is close up and in high definition. This results in focus on individual components with pro and con arguments for every variety and pattern of nutrition and supplementation. Yet, the game really has not changed; obesity remains a social and cultural challenge, no absolute solution has been discovered.

Those looking to improve their body composition— increase or maintain lean mass while reducing body fat— struggle for some semblance of credibility in the realm of nutritional advice. Somehow, mentioning protein now validates a diet program. People are programmed to nod their heads when a nutritionist (qualified or not) mentions the presence of protein. “Look! There’s protein!” If it can be packaged in a shiny box, one could start a cult. Certainly, it is critical to understand the role proteins play in nutrition and metabolism. Additionally, there are benefits derived from consuming certain types or quantities of protein while pursuing weight loss. However, for the purpose of contributing to weight-loss efforts or weight management, protein can be both simple and complex.

The “simple” of protein is that it is necessary for building structural tissue and functional molecules, but can also serve as a source of energy or calories. The “official” word on protein is that a person needs 0.8 grams of protein per kilogram of bodyweight daily. That amount will prevent short-term loss of lean mass in a sedentary person. It is like saying one needs only 60 milligrams of vitamin C to prevent scurvy. Let’s deal with reality for a moment and use pounds, as the introduction of the metric system to the U.S. consumer failed 40 years ago; also, those who truly care about their personal nutrition are not sedentary. The recommendation for protein intake in a physically active person is 1.6 to 1.8 grams per kilogram of bodyweight per day— meaning the old adage used for decades of one gram per POUND of bodyweight daily is pretty much spot on.1 [There are 2.2 pounds per kilogram]

Finding the “Sweet Spot” of Protein Consumption

Now, having been to the Golden Corral buffet, I have seen people attempt (and succeed) to ingest more than 200 grams of protein in a single meal— accompanied by a diet soda. However, the protein not only needs to be ingested (i.e., eaten), it also has to be digested, absorbed by the intestines, and finally assimilated into the various tissues of the body (e.g., skeletal muscle). It just is not practical to consume that much protein at once.

While the “sweet spot” of protein consumed in a single meal remains to be discovered, despite the self-promotional proclamations of one study, there is a ceiling on what each person can productively consume. There are a number of variables that need be accounted for, such as: lean mass; postprandial versus post-absorptive state (i.e., time passed since last meal); habitual diet; activity; hormonal status; age; etc. Gender does not appear to be a significantly relevant factor. One study that offers insight, though is not as conclusive as it has been stated, suggests 20 grams of protein in a single meal maximizes muscle protein synthesis. Beyond that, additional protein is preferentially diverted into gluconeogenesis or ketogenesis— protein breakdown pathways that produce sugar or ketones which are used for producing (or being stored as) energy.2 This study produced valuable data, but the design and statistical power had certain flaws that were addressed by the authors in their discussion. Other studies show increased muscle protein synthesis at levels of 30 and 36 grams of protein.3-5

Using another rule of thumb— 10 calories per pound of bodyweight per day for a hypocaloric intake in a moderately active person— this means that of 2,000 total daily calories, up to 40 percent would be protein. For some people, this number may be adjusted down. Performance athletes, or people who perform a lot of higher intensity, long-duration exercise, benefit from a higher carbohydrate intake to replenish muscle and liver stores of glycogen (sugar stores). Recall, past a certain point, protein begins to be used for energy instead of tissue building. Also, when sugar stores become depleted during physical stress, the body breaks down muscle protein to provide needed energy (in addition to the contribution from fatty acids).

Thus, a tennis player or cyclist may substitute about 50 grams of protein for 50 grams of carbohydrate in their daily total. It is generally accepted that performance athletes do best with approximately 55 percent carbohydrate to meet the metabolic demands of their training. So, for a resistance-trained athlete or recreational fitness person seeking to improve body composition, a diet may consist of 40 percent carbohydrate/40 percent protein/20 percent fat; a performance athlete may see a diet closer to 55/30/15.

Metabolic Response to Dietary Protein

The “complex” of protein refers to the metabolic response to dietary protein or specific amino acids, as well as the probable contribution from associated fat consumed with animal protein. Realize that these points supporting the power of protein compare the results against diets or meals low in protein. A low-protein meal may have 5 percent protein, or contain less than 10 grams total protein.

Protein promotes weight loss by increasing satiety, improving body composition and increasing calorie expenditure through thermogenesis. Satiety is part of appetite. You can reduce appetite by either suppressing hunger or increasing satiety. There are complementary tracts in the brain controlling each component. When you suppress hunger, you delay or reduce food seeking. When you increase satiety, the urge to consume is satisfied earlier and with less. By increasing satiety, protein reduces the number of calories consumed in a meal, and possibly in subsequent meals.6-8 A related effect is noted with certain proteins in decreasing a hormone known to signal hunger, providing a two-pronged attack against hunger and overeating.9,10 The resulting difference between a diet that includes eggs at breakfast versus the more typical “milk and cereal” may be on the order of 500 calories less each day.9

Surprisingly, whey does not induce satiety as long or reliably. Yet, another study showed whey to be more effective at reducing the appetite four hours later, compared to tuna, egg and turkey protein.13 Another surprise lies in the power of gelatin as a protein in promoting satiety. Cheap, low in BCAAs, easy to make and maligned; gelatin is about 40 percent more potent in promoting satiety, resulting in 20 percent fewer calories consumed.14 Another weight-loss powerhouse protein rarely considered for this ability is fish protein. Blinded by the benefits of omega-3 fatty acids, people fail to appreciate the research showing fish protein to be a superior protein for promoting weight loss.15,16 A brief mention should be made that dietary fat does not appear to promote satiety, leading to overeating.17 In fact, high-fat diets blunt the signals involved in appetite suppression. Protein also increases energy expenditure, and not just by supporting the maintenance or building of lean mass during a hypocaloric diet. It is well understood that additional protein during a low-calorie diet protects against the loss of muscle, and muscle mass has a direct relationship with the number of calories a person burns daily.18,19

Thermogenesis and Weight Loss

There is an underappreciated calorie-burning effect of protein that also contributes to weight loss— thermogenesis. This refers to the effect protein in the diet has on generating heat instead of energy with its caloric energy— it is literally “calorie burning.” People are likely familiar with thermogenic weight-loss supplements, such as the days of ephedrine and caffeine products. However, the energy required to digest and absorb protein causes the intestines to generate heat, much like your car engine getting hot as it runs faster.20 Also, if the protein source contains fat, bile will be released from the gallbladder that contains bile acids. It is interesting that unsaturated fats (e.g., olive oil) increase calorie loss and thermogenesis much greater than saturated fat.21 Bile acids interact with receptors in a specialized tissue called brown fat to generate heat by “wasting” calories as heat.22 Lastly, the intestines release hormones during digestion that activate brown fat in addition to the effect of bile acids.23 Also, regular meal patterns improve the thermic effect of meals.24 People may be exposed to this kind of meal variability on weekends, or while traveling, as schedules are less regimented.

Take-Home Message

What is the take-home message? It doesn’t require much, but ensuring that an adequate amount of protein is present in each meal will aid in maximizing the weight-loss effect of dieting while protecting against lean muscle loss. The power of protein lies in its ability to reduce the appetite, and maintain the metabolism while following a hypocaloric diet, compared to a low-protein plan. It seems that a breakfast with eggs, a protein shake or two, and a nice fish dinner would be not only healthy and effective, but delicious and satisfying as well.

1. Churchward-Venne TA, Murphy CH, et al. Role of protein and amino acids in promoting lean mass accretion with resistance exercise and attenuating lean mass loss during energy deficit in humans. Amino Acids 2013;45:231-40.

2. Witard OC, Jackman SR, et al. Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise. Am J Clin Nutr 2014;99:86-95.

3. Areta JL, Burke LM, et al. Reduced resting skeletal muscle protein synthesis is rescued by resistance exercise and protein ingestion following short-term energy deficit. Am J Physiol Endocrinol Metab 2014;306:E989-97.

4. Yang Y, Breen L, et al. Resistance exercise enhances myofibrillar protein synthesis with graded intakes of whey protein in older men. Br J Nutr 2012;108:1780-8.

5. Robinson MJ, Burd NA, et al. Dose-dependent responses of myofibrillar protein synthesis with beef ingestion are enhanced with resistance exercise in middle-aged men. Appl Physiol Nutr Metab 2013;38:120-5.

6. Leidy HJ, Ortinau LC, et al. Beneficial effects of a higher-protein breakfast on the appetitive, hormonal, and neural signals controlling energy intake regulation in overweight/obese, “breakfast-skipping,” late-adolescent girls. Am J Clin Nutr 2013;97:677-88.

7. Westerterp-Plantenga MS, Lemmens SG, et al. Dietary protein – its role in satiety, energetics, weight loss and health. Br J Nutr 2012;108 Suppl 2:S105-12.

8. Douglas SM, Ortinau LC, et al. Low, moderate, or high protein yogurt snacks on appetite control and subsequent eating in healthy women. Appetite 2013;60:117-22.

9. Fallaize R, Wilson L, et al. Variation in the effects of three different breakfast meals on subjective satiety and subsequent intake of energy at lunch and evening meal. Eur J Nutr 2013;52:1353-9.

10. Bayham BE, Greenway FL, et al. A randomized trial to manipulate the quality instead of quantity of dietary proteins to influence the markers of satiety. J Diabetes Complications 2014 Feb 13. [E-pub, ahead of print]

11. Lam SM, Moughan PJ, et al. The influence of whey protein and glycomacropeptide on satiety in adult humans. Physiol Behav 2009;96:162-8.

12. Bendtsen LQ, Lorenzen JK, et al. Effect of dairy proteins on appetite, energy expenditure, body weight, and composition: a review of the evidence from controlled clinical trials. Adv Nutr 2013;4:418-38.

13. Pal S, Ellis V. The acute effects of four protein meals on insulin, glucose, appetite and energy intake in lean men. Br J Nutr 2010;104:1241-8.

14. Veldhorst MA, Nieuwenhuizen AG, et al. A breakfast with alpha-lactalbumin, gelatin, or gelatin + TRP lowers energy intake at lunch compared with a breakfast with casein, soy, whey, or whey-GMP. Clin Nutr 2009;28:147-55.

15. Ramel A, Jonsdottir MT, et al. Consumption of cod and weight loss in young overweight and obese adults on an energy reduced diet for 8 weeks. Nutr Metab Cardiovasc Dis 2009;19:690-6.

16. Thorsdottir I, Tomasson H, et al. Randomized trial of weight-loss-diets for young adults varying in fish and fish oil content. Int J Obes 2007;31:1560-6.

17. Strik CM, Lithander FE, et al. No evidence of differential effects of SFA, MUFA or PUFA on post-ingestive satiety and energy intake: a randomised trial of fatty acid saturation. Nutr J 2010;9:24(12 pp).

18. Tang M, Armstrong CL, et al. Normal vs. high-protein weight loss diets in men: effects on body composition and indices of metabolic syndrome. Obesity 2013;21:E204-10.

19. Meckling KA, Sherfey R. A randomized trial of a hypocaloric high-protein diet, with and without exercise, on weight loss, fitness, and markers of the Metabolic Syndrome in overweight and obese women. Appl Physiol Nutr Metab 2007;32:743-52.

20. Johnston CS, Day CS, et al. Postprandial thermogenesis is increased 100% on a high-protein, low-fat diet versus a high-carbohydrate, low-fat diet in healthy, young women. J Am Coll Nutr 2002;21:55-61.

21. Krishnan S, Cooper JA. Effect of dietary fatty acid composition on substrate utilization and bodyweight maintenance in humans. Eur J Nutr 2014;53:691-710.

22. Chen X, Lou G, et al. TGR5: a novel target for weight maintenance and glucose metabolism. Exp Diabetes Res. 2011:853501(5 pp).

23. van den Beukel JC, Grefhorst A. Interactions between the Gut, the Brain and Brown Adipose Tissue Function. Front Horm Res 2014;42:107-22.

24. Farshchi HR, Taylor MA, et al. Decreased thermic effect of food after an irregular compared with a regular meal pattern in healthy lean women. Int J Obes Relat Metab Disord 2004;28:653-60.