Objective: To examine the effects of dietary protein and obesity classification on energy-restriction-induced changes in weight, body composition, appetite, mood, and cardiovascular and kidney health.
Research methods and procedures: Forty-six women, ages 28 to 80, BMI 26 to 37 kg/m(2), followed a 12-week 750-kcal/d energy-deficit diet containing higher protein (HP, 30% protein) or normal protein (NP, 18% protein) and were retrospectively subgrouped according to obesity classification [pre-obese (POB), BMI = 26 to 29.9 kg/m(2); obese (OB), BMI = 30 to 37 kg/m(2)).
Results: All subjects lost weight, fat mass, and lean body mass (LBM; p < 0.001). With comparable weight loss, LBM losses were less in HP vs. NP (-1.5 +/- 0.3 vs. -2.8 +/- 0.5 kg; p < 0.05) and POB vs. OB (-1.2 +/- 0.3 vs. -2.9 +/- 0.4 kg; p < 0.005). The main effects of protein and obesity on LBM changes were independent and additive; POB-HP lost less LBM vs. OB-NP (p < 0.05). The energy-restriction-induced decline in satiety was less pronounced in HP vs. NP (p < 0.005). Perceived pleasure increased with HP and decreased with NP (p < 0.05). Lipid-lipoprotein profile and blood pressure improved and kidney function minimally changed with energy restriction (p < 0.05), independently of protein intake.
Discussion: Consuming a higher-protein diet and accomplishing weight loss before becoming obese help women preserve LBM. Use of a higher-protein diet also improves perceptions of satiety and pleasure during energy restriction.