Protein intake during energy restriction: effects on body composition and markers of metabolic and cardiovascular health in postmenopausal women

OBJECTIVE: The primary aim of this study was to assess the effects of dietary protein intake on energy restriction (ER)-induced changes in body mass and body composition. Clinical markers of metabolic and cardiovascular diseases were also measured. DESIGN: 54 postmenopausal women, age 58 +/- 2 y, body mass index 29.6 +/- 0.8 kg/m(2), were assigned to one of four groups. For 9 weeks, three ER groups ate a 1000 kcal/d lacto-ovo vegetarian basal diet plus 250 kcal/d of either beef (BEEF, n = 14), chicken (CHICKEN, n = 15), or carbohydrate/fat foods (CARB (lacto-ovo), n = 14), while a control group (CON, n = 11) consumed their habitual diets. RESULTS: Energy intake was lower in the ER groups compared to CON (BEEF, 1114 +/- 155 kcal/d, CHO: PRO: FAT, 46:24:30 % of energy intake; CHICKEN, 1098 +/- 203 kcal/d, 51:25:24; CARB 1158 +/- 341 kcal/d, 59:17:24; CON, 1570 +/- 633 kcal/d, 47:20:33), but did not differ among ER groups. For all ER subjects combined, body mass (-6.7 +/- 2.4 kg, 9 %), fat mass (-4.6 +/- 1.9 kg, 13 %), and fat-free mass (-2.1 +/- 1.1 kg, 5 %) decreased. These responses did not differ among the ER groups, except for body mass (CHICKEN -7.9 +/- 2.6 kg(a); BEEF -6.6 +/- 2.7 kg(a,b); CARB -5.6 +/- 1.8 kg(b); CON -1.2 +/- 1.2 kg(c); values with a difference superscript differ, p