Moderate protein intake improves total and regional body composition and insulin sensitivity in overweight adults.

A high protein intake (approximately 40% of energy intake) combined with aerobic and resistance exercise training is more closely associated with improved body composition and cardiovascular risk profile than a traditional protein intake (approximately 15% of intake) combined with moderate-intensity aerobic exercise. However, there is concern that such high-protein diets may adversely affect health. We therefore tested the hypothesis that moderate protein intake (approximately 25% of energy intake) would elicit similar benefits on body composition and metabolic profile as high protein intake. Twenty-four overweight/obese men and women (body mass index [BMI] = 32.2 +/- 3.4, percentage of body fat [%BF] = 37.3 +/- 8.0) were matched for BMI and %BF and randomly assigned to one of 3 groups for a 3-month nutrition/exercise training intervention: (1) high-protein diet (approximately 40% of energy intake) and combined high-intensity resistance and cardiovascular training (HPEx, n = 8, 5 female and 3 male), (2) moderate-protein diet (approximately 25% of energy intake) and combined high-intensity resistance and cardiovascular training (MPEx, n = 8, 5 female and 3 male), or (3) high-protein diet only (HPNx, n = 8, 5 female and 3 male). Total and regional body composition (dual-energy x-ray absorptiometry), insulin sensitivity (insulin sensitivity index to the oral glucose tolerance test), insulin-like growth factor-1 (IGF-1), IGF binding protein-1 (IGFBP-1), IGF binding protein-3 (IGFBP-3), and blood lipids were measured at baseline and after the intervention. All groups experienced significant (P < .05) and similar losses of body weight, BMI, and total and abdominal %BF, and similar improvements in insulin sensitivity (HPEx, 6.3 +/- 1.2 vs 9.5 +/- 0.98; MPEx, 6.2 +/- 1.4 vs 8.4 +/- 1.6; HPNx, 3.7 +/- 1.1 vs 7.0 +/- 1.1; insulin sensitivity index to the oral glucose tolerance test; P < .05) and leptin levels. Furthermore, the HPEx group demonstrated decreases in total cholesterol (TC) and triglycerides, and increases in IGF-1 and IGFBP-1. The MPEx group experienced decreases in TC, whereas the HPNx group had increases in high-density lipoprotein cholesterol, TC to high-density lipoprotein, IGF-1, and IGFBP-1. In conclusion, moderate protein intake elicits similar benefits in body composition and insulin sensitivity as a high-protein diet. These findings may have practical implications for individuals interested in diets containing elevated dietary protein.

Increased dietary protein and combined high intensity aerobic and resistance exercise improves body fat distribution and cardiovascular risk factors.

We investigated the effectiveness of two lifestyle modification programs of exercise training and nutritional intake (ad libitum) on improving body composition and disease risk in overweight/obese men and women. Sixty-three subjects were weight matched and assigned to one of three groups for a 12 wk intervention: (1) high-intensity resistance and cardiovascular training and a balanced diet (RC+BD, 40% CHO: 40% PRO; n=27, 16 female/11 male, age = 42 +/- 9 y); (2) moderate-intensity cardiovascular training and a traditional food guide pyramid diet (C+TD, CHO 50 to 55%; PRO 15 to 20%; FAT < 30%; n=19, 10 female/9 male, age = 43 +/- 10 y); and (3) an inactive control group (C, n=17, 5 female/12 male, age 43 +/- 11 y). RC+BD resulted in more favorable changes (P < 0.01) in percent body fat (-15.8% vs. -6.9%) and abdominal fat (-15.6% vs. -7.5%) compared to C+TD and C. Total cholesterol (-13.8%), LDL-cholesterol (-20.8%), and systolic blood pressure (-5.7%) declined (P > 0.05) in RC+BD, whereas C+TD and C remained unchanged. Our results suggest that RC+BD may be more effective than C+TD and C in enhancing body composition and lowering cardiovascular risk in obese individuals.