Protein intake and lean body mass preservation during energy intake restriction in overweight older adults

BACKGROUND: Dietary-induced weight loss is generally accompanied by a decline in skeletal muscle mass. The loss of muscle mass leads to a decline in muscle strength and impairs physical performance. A high dietary protein intake has been suggested to allow muscle mass preservation during energy intake restriction. OBJECTIVE: To investigate the impact of increasing dietary protein intake on lean body mass, strength and physical performance during 12 weeks of energy intake restriction in overweight older adults. DESIGN: Sixty-one overweight and obese men and women (63+/-5 years) were randomly assigned to either a high protein diet (HP; 1.7 g kg-1 per day; n=31) or normal protein diet (NP; 0.9 g kg-1 per day; n=30) during a 12-week 25% energy intake restriction. During this controlled dietary intervention, 90% of the diet was provided by the university. At baseline and after the intervention, body weight, lean body mass (dual-energy X-ray absorptiometry), leg strength (1-repetition maximum), physical performance (Short Physical Performance Battery, 400 m) and habitual physical activity (actigraph) were assessed. RESULTS: Body weight declined in both groups with no differences between the HP and NP groups (-8.9+/-2.9 versus -9.1+/-3.4 kg, respectively; P=0.584). Lean body mass declined by 1.8+/-2.2 and 2.1+/-1.4 kg, respectively, with no significant differences between groups (P=0.213). Leg strength had decreased during the intervention by 8.8+/-14.0 and 8.9+/-12.8 kg, with no differences between groups (P=0.689). Physical performance as measured by 400 m walking speed improved in both groups, with no differences between groups (P=0.219). CONCLUSIONS: Increasing protein intake above habitual intake levels (0.9 g kg-1 per day) does not preserve lean body mass, strength or physical performance during prolonged energy intake restriction in overweight older adults.International Journal of Obesity advance online publication, 3 November 2015; doi:10.1038/ijo.2015.182.