Although many people suggest that weight loss is just attributed to the energy balance (calories in vs. calories out) which to some extent it is, this would suggest eating 100 calories (kcal) of nuts to have the same effect on the body as 100kcals of sweets. So why would nuts be the obvious better choice when dieting?

Put simply, a calorie IS a calorie – containing 4.184 joules of energy. However when it comes to nutrition the impact of a calorie on the body is not as simple you might think, all foods have different properties which impact the body in different ways. To demonstrate this, one study found two weeks of overfeeding on candy vs. peanuts to only increase waist circumference in the candy group, even though both groups had an identical increase in calorie intake, suggesting different metabolic effects of foods.

This is where the thermic effect of food is often referenced – the caloric cost of digesting and processing different foods, which accounts for around 10% of calories burned per day. It was noted in the 19^th century that protein has a much higher thermic effect (requiring more energy to digest and process) than carbohydrates or fat (which are a lot easier to metabolise). The thermic effect of protein is thought to be around 20-30% whilst 5-10% for carbohydrates and just 0-3% for fats. This means if someone was to eat 200 calories of protein, the body is likely to use between 40 and 60kcal just in digestion.

So, does this mean certain foods may be more beneficial for improved weight management? A recent study set to find out if a high protein directly affected the body composition of resistance trained men and women. When compared to a control group, a high protein diet (4.4g/kg/d – more than five times the recommended daily allowance!) was found to have no effect on body composition and did not result in a gain in fat mass, despite the high protein group consuming over 800kcal more per day for a period of eight weeks!

This study certainly dispels the myth of a calorie just being a calorie, suggesting that it may be more difficult to gain body weight when over consuming protein, potentially due its high thermic effect. Similar studies involving overconsumption of carbohydrates have consistently led to a gain in fat mass, highlighting that a diet higher in protein and lower in carbohydrates may be beneficial to weight management, especially along with exercise.

As the study only investigated the impacts of a VERY high protein diet in resistance trained individuals, the results may be different in those who exercise little or not at all, not to mention the possible influence of many other variables. In addition to this, much of the protein consumed in the study was from whey protein powder which is said to have a greater thermic effect than other sources.

Whilst this is not an excuse to over consume protein, it does give implications that a high protein diet may be effective along with exercise in improving weight management. Not only for its higher thermic effect but also due to its beneficial effects on satiety and the retention of lean muscle mass, which have been noted in many other studies.

Adie Blanchard – Researcher

References

Antonio, J., Peacock, C. A., Ellerbroek, A., Fromhoff, B., & Silver, T. (2014). The effects of consuming a high protein diet (4.4 g/kg/d) on body composition in resistance-trained individuals. Journal of the International Society of Sports Nutrition, 11(1), 19.

Claesson, A. L., Holm, G., Ernersson, Å., Lindström, T., & Nystrom, F. H. (2009). Two weeks of overfeeding with candy, but not peanuts, increases insulin levels and body weight. Scandinavian Journal of Clinical & Laboratory Investigation, 69(5), 598-605.

Paddon-Jones, D., Westman, E., Mattes, R. D., Wolfe, R. R., Astrup, A., & Westerterp-Plantenga, M. (2008). Protein, weight management, and satiety. The American Journal of Clinical Nutrition, 87(5), 1558S-1561S.

Tappy, L. (1996). Thermic effect of food and sympathetic nervous system activity in humans. Reproduction Nutrition Development, 36(4), 391-397.