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.

Satiety and energy intake after single and repeated exposure to gel-forming dietary fiber: post-ingestive effects.

BACKGROUND: Viscous or gel-forming dietary fibers can increase satiety by a more firm texture and increased eating time. Effects of viscous or gel-forming fibers on satiety by post-ingestive mechanisms such as gastric emptying, hormonal signals, nutrient absorption or fermentation are unclear. Moreover, it is unclear whether the effects persist after repeated exposure. OBJECTIVE: To investigate satiety and energy intake after single and repeated exposure to gelled fiber by post-ingestive mechanisms. DESIGN: In a two-arm crossover design, 32 subjects (24 female subjects, 21±2 y, BMI 21.8±1.9 kg m(-2)) consumed test foods once daily for 15 consecutive days, with 2 weeks of washout. Test foods were isocaloric (0.5 MJ, 200 g) with either 10 g gel-forming pectin or 3 g gelatin and 2 g starch, matched for texture and eating time. Hourly satiety ratings, ad libitum energy intake and body weight were measured on days 1 (single exposure) and 15 (repeated exposure). In addition, hourly breath hydrogen, fasting glucose, insulin, leptin and short-chain fatty acids were measured. RESULTS: Subjects rated hunger, desire to eat and prospective intake about 2% lower (P<0.015) and fullness higher (+1.4%; P=0.041) when they received pectin compared with control. This difference was similar after single and repeated exposure (P>0.64). After receiving pectin, energy intake was lower (-5.6%, P=0.012) and breath hydrogen was elevated (+12.6%, P=0.008) after single exposure, but not after repeated exposure. Fasting glucose concentrations were higher both after single and repeated exposure to pectin (+2.1%, P=0.019). Body weight and concentrations of insulin, leptin and short-chain fatty acids did not change during the study. CONCLUSIONS: Gelled pectin can increase satiety and reduce energy intake by post-ingestive mechanisms. Although the effects were small, the effects on satiety were consistent over time, whereas the effects on energy intake reduction were not.