The effects of dietary protein on weight loss seem to be an ongoing dilemma for scientists. Putting forth another side to it, a team from the American Medical Association has assessed the influences of high, low and normal consumption of protein diets on weight loss or gain, energy metabolism and body constitution.
This analysis was a single-blind randomized controlled trial that constituted 25 healthy male and female volunteers whose body weight was steady. The participants were in the age-group 18 to 35 with a BMI in the range 19 to 30.
Firstly, the subjects were overfed with a weight-stabilizing diet for a span of 13 to 25 days, after which they were categorized into 3 groups. Each of these sets was exposed to diets comprising 5% protein falling under the low protein group, 15% protein considered to be the normal protein group and 25% protein regarded as the high protein group.
As per the outcomes of the study, the protein diet apparently accounted for 40% excess energy intake as compared to the energy attained in the weight stabilization period. This percentage is estimated to be equivalent to 954kcal/d.
Notably, overeating seemed to result in less weight gain in the low-protein diet group than the normal protein diet and the high protein diet set. Body mass appeared to elevate in a similar manner in all 3 groups presenting almost 50% to above 90% additional calories. The resting energy expenditure, cumulative energy expenditure and body protein did not supposedly increase via overfeeding of low-protein diet. However, the same parameters apparently elevated to a large extent in case of normal and high protein diets.
The scientists concluded that calories alone are responsible for weight gain, while proteins play a role in energy expenditure and storage of lean body mass and not body fat. This study is published in JAMA.