I do a lot of weight training and take in my 1.6g/kg per day amount of protein as a woman. The amount for men is 1.8g/kg per day. One of the concerns of weight trainers is if they eat too much protein that it will turn to fat in the body. How many protein shakes should I really be drinking?. In this blog post we determine ‘fat’ from fiction and discover if eating a high protein diet leads to an increase in body fat.
Study of Low, Normal and High Protein Diet
In order to test the hypothesis that protein from a high protein diet gets turned into fat, researches took a sample of 25 healthy individuals. They ranged between 18 and 35 years of age from the Baton Rouge, Louisiana community in the US.
Researchers divided the group of people into 3 groups – low, normal (15% energy from protein) and a high protein diet (25% energy from protein) protein diets. They kept the level of carbohydrates the same (around 40%). This equated to 47g/d of protein for low protein, 139 g/d for the normal protein and 228 g/d for the high protein diet. The amount they were overfed was 40% more than weight maintenance energy expenditure. The amount of calories that were eaten was the same between all participants.
Before the study they performed baseline measures for total energy expenditure and body composition (body weight, lean body mass, fat mass).
After 56 days of over feeding all groups put on weight and the average amount of fat mass that was put on was 3.51 kg (95% CI, 3.06 to 3.96 kg). There was no statistically significant difference between the 3 groups. This meant that they all added fat to their body independent of the amount of protein that they ate. Notably, the low protein diet put the least amount of weight on. This was because they didn’t put on any muscle mass. There was also an increase in resting metabolism but this was due to the fact that the participants all put muscle mass on.
What Does This Mean?
What we can gather from the study is that calories alone were the reason that the men put the weight on and not the amount of protein that they were eating. However the extra protein were responsible for the increase in lean body mass but not fat mass. So this means that a high protein diet doesn’t lead to an increase in body fat.
George A. Bray, MD, Steven R. Smith, MD, Lilian de Jonge, PhD, Hui Xie, PhD, Jennifer Rood, PhD, Corby K. Martin, PhD, Marlene Most, PhD, Courtney Brock, MS, RD, Susan Mancuso, BSN, RN, and Leanne M. Redman, , ‘Effect of Dietary Protein Content on Weight Gain, Energy Expenditure, and Body Composition During Overeating’, JAMA. 2012 Jan 4; 307(1): 47–55.