Nutrition

February 6, 2011

It’s the Protein, Dummies!

From a nutrition perspective, we can look back at the 80’s as the low-fat decade where consumption of as little dietary fat as possible was believed to be the key to weight management. The 90’s saw a backlash to this notion and hence became the low carb era where steak and eggs became standard fare. Today, consumers are understandably confused as to the best way to eat. Meanwhile, the low carb vs. high carb debate continues to rage on.

A recent ABC news article titled May the Best Calorie Lose explored the subject of whether certain eating styles may have a bearing on weight loss, above and beyond simply consuming fewer calories than you expend. While the article does make for good theater, both sides in the debate seem to be missing the boat.

On a basic level, it *is* calories that count. This is consistent with Newton’s First Law of Thermodynamics, which states that energy can neither be created or destroyed, only transferred from one form to another. Thus, if you consume more calories than you expend, you will gain weight; if you expend more calories than you consume, you’ll lose weight. Mark Haub’s recent experiment with the Twinkie Diet is ‘Exhibit A’ in support of the concept. Simple, right? Well, not exactly…

In vivo (i.e. within living subjects), there are mitigating conditions by which the body can become either more or less efficient at utilizing calories for energy production. So while over the short term you will lose weight simply by cutting calories below maintenance levels, over the long term the types of foods you eat will indeed have an effect on weight management. Unfortunately, those in the “low carb” and “high carb” camps are both off-base in their focus on the subject.

Fact is, neither carbs nor fat are inherently “evil.” Rather, it’s the *types* of carbs and fat that have the greater effect on weight maintenance. There is a big difference between consuming a slice of Wonder bread and a bowl of steel cut oatmeal. Yes, both are carbohydrates, but their effect on the body couldn’t be more different. Similarly, there is a big difference between consuming salmon versus bacon, despite both containing copious amounts of dietary fat (hint: the omega-3 fats in salmon are heart healthy and highly bioactive compared to the saturated fat in bacon). This is why it is silly for the nutritionist in the above article to cite a study comparing consumption of candy versus peanuts, and claim that it supports a low carb lifestyle. It’s an apples to oranges argument.

Yet the most important aspect of diet which seems to escape many nutritional professionals is the effect of protein consumption on body composition–irrespective of carbs or fat. Pure and simple, protein is the most important nutrient in your diet. For one, eating protein creates a sensation of satiety (i.e. fullness) that leaves a person feeling satisfied after a meal. The prevailing body of research studies show that protein induces a greater effect on satiety than either carbs or fat (1, 2, 3). It is believed this may be due to the effects of protein on various hormones involved in signaling the brain as to whether or not you are full (4, 5).

Proetin also has a much greater thermic effect than either carbs or fat. This phenomenon, called the thermic effect of food (TEF), describes the energy cost associated with digestion. The TEF of protein is approximately 25-30% of calories while that of carbs is generally determined to be less than 10%. Dietary fat has a negligible thermic effect, depending on the type of fat consumed. Studies show that because of the TEF, diets higher in protein exert a larger effect on energy expenditure than diets lower in protein, and can even help to attenuate weight gain during times of overfeeding (6).

Lastly, and perhaps most importantly, protein consumption helps to preserve lean mass (read: muscle tissue) during dieting. For every pound lost on a diet the typical “normal” protein diet (at levels prescribed by the RDA), approximately 1/3 of a pound comes from the breakdown of muscle tissue. Remember that muscle is metabolically active tissue and its loss will inevitably cause a slowing of your metabolism and subsequent weight regain. The only way to counteract this occurrence is by consuming extra protein. Keeping protein intake high helps to preserve lean tissue, preventing the negative consequences of muscle wasting (7, 8, 9).

So how much protein should you consume. The RDA for protein intake is 0.8 grams/kilogram of body weight. By all accounts, this is too low, even for couch potatoes. Recent research shows that elderly individuals lose functional ability when following the RDA guidelines resultant to losses in lean mass (10). Studies show that physically active individuals need approximately 1.4 to 2.0 grams per kilogram of body weight, depending on types and intensity of exercise (11). My general recommendation is to round this off and consume approximately one gram of protein per pound of ideal body weight (i.e. the weight you aspire to being when you are at your leanest). This provides a margin of safety, ensuring you never fall into negative nitrogen balance. And in case you’re worried about negative health effects, rest easy. As long as you have healthy kidney function, research has debunked the claims that higher protein diets will put you on dialysis.

Stay Fit!

Brad

1. Leidy HJ, Armstrong CL, Tang M, Mattes RD, Campbell WW. The influence of higher protein intake and greater eating frequency on appetite control in overweight and obese men. Obesity (Silver Spring). 2010 Sep;18(9):1725-32.

2. Westerterp-Plantenga MS, Rolland V, Wilson SA, Westerterp KR. Satiety related to 24 h diet-induced thermogenesis during high protein/carbohydrate vs high fat diets measured in a respiration chamber. Eur J Clin Nutr. 1999 Jun;53(6):495-502.

3. Hill AJ, Blundell JE: Macronutrients and satiety; The effects of a high protein or high carbohydrate meal on subjective motivation to eat and food preferences. Nutr Behav 3:133–144, 1986.

4. Leidy HJ, Mattes RD, Campbell WW. Effects of acute and chronic protein intake on metabolism, appetite, and ghrelin during weight loss. Obesity (Silver Spring). 2007 May;15(5):1215-25.

5. Bowen J, Noakes M, Trenerry C, Clifton PM. Energy intake, ghrelin, and cholecystokinin after different carbohydrate and protein preloads in overweight men. J Clin Endocrinol Metab 2006; 91: 1477–148

6. Halton TL, Hu FB. The effects of high protein diets on thermogenesis, satiety and weight loss: a critical review. J Am Coll Nutr. 2004 Oct;23(5):373-85. Review.

7. Leidy HJ, Carnell NS, Mattes RD, Campbell WW. Higher protein intake preserves lean mass and satiety with weight loss in pre-obese and obese women. Obesity (Silver Spring). 2007 Feb;15(2):421-9.

8. Blackburn, GL. Protein requirements with very low calorie diets. Postgrad Med J. 1984;60 Suppl 3:59-65.

9. Piatti PM, Monti F, Fermo I, Baruffaldi L, Nasser R, Santambrogio G, Librenti MC, Galli-Kienle M, Pontiroli AE, Pozza G. Hypocaloric high-protein diet improves glucose oxidation and spares lean body mass: comparison to hypocaloric high-carbohydrate diet. Metabolism 1994 Dec;43(12):1481-7

10. Campbell WW, Trappe TA, Wolfe RR, Evans WJ. The recommended dietary allowance for protein may not be adequate for older people to maintain skeletal muscle. J Gerontol A Biol Sci Med Sci. 2001 Jun;56(6):M373-80.

11. Campbell B, Kreider RB, Ziegenfuss T, La Bounty P, Roberts M, Burke D, Landis J, Lopez H, Antonio J. International Society of Sports Nutrition Position Stand: Protein and Exercise. J Int Soc Sports Nutr. 2007;4:8