No significant differences were observed for weight , waist circumference , fat mass , blood lipids ( i.e. total cholesterol , LDL-cholesterol , HDL-cholesterol , triacylglycerols ) , C-reactive protein , diastolic and systolic blood pressure , fasting glucose and glycosylated hemoglobin .
Sensitivity analysis of high quality RCTs confirmed the data of the primary analyses , while exclusion of studies with diabetic subjects result ed in an additional benefit of high-protein diets with respect to a more marked increase in HDL-cholesterol .
Conclusion According to the present meta- analysis of long-term RCTs , high-protein diets exerted neither specific beneficial nor detrimental effects on outcome markers of obesity , cardiovascular disease or glycemic control .
Background Meta-analyses of short-term studies indicate favorable effects of higher protein vs. lower protein diets on health outcomes like adiposity or cardiovascular risk factors , but their long-term effects are unknown .
A moderate-protein diet produces sustained weight loss and long-term changes in body composition and blood lipids in obese adults.
Diets with increased protein and reduced carbohydrates ( PRO ) are effective for weight loss , but the long-term effect on maintenance is unknown . This study compared changes in body weight and composition and blood lipids after short-term weight loss ( 4 mo ) followed by weight maintenance ( 8 mo ) using moderate PRO or conventional high-carbohydrate ( CHO ) diets .  Participants ( age = 45.4 + /- 1.2 y ; BMI = 32.6 + /- 0.8 kg/m(2 ) ; n = 130 ) were r and omized to 2 energy-restricted diets ( -500 kcal/d or -2093 kJ/d ) : PRO with 1.6 g x kg(-1 ) x d(-1 ) protein and < 170 g/d carbohydrates or CHO with 0.8 g x kg(-1 ) x d(-1 ) protein , > 220 g/d carbohydrates . At 4 mo , the PRO group had lost 22 % more fat mass ( FM ) ( -5.6 + /- 0.4 kg ) than the CHO group ( -4.6 + /- 0.3 kg ) but weight loss did not differ between groups ( -8.2 + /- 0.5 kg vs. -7.0 + /- 0.5 kg ; P = 0.10 ) . At 12 mo , the PRO group had more participants complete the study ( 64 vs. 45 % , P < 0.05 ) with greater improvement in body composition ; however , weight loss did not differ between groups ( -10.4 + /- 1.2 kg vs. -8.4 + /- 0.9 kg ; P = 0.18 ) . Using a compliance criterion of participants attaining > 10 % weight loss , the PRO group had more participants ( 31 vs. 21 % ) lose more weight ( -16.5 + /- 1.5 vs. -12.3 + /- 0.9 kg ; P < 0.01 ) and FM ( -11.7 + /- 1.0 vs. -7.9 + /- 0.7 kg ; P < 0.01 ) than the CHO group . The CHO diet reduced serum cholesterol and LDL cholesterol compared with PRO ( P < 0.01 ) at 4 mo , but the effect did not remain at 12 mo . PRO had sustained favorable effects on serum triacylglycerol ( TAG ) , HDL cholesterol ( HDL-C ) , and TAG : HDL-C compared with CHO at 4 and 12 mo ( P < 0.01 ) . The PRO diet was more effective for FM loss and body composition improvement during initial weight loss and long-term maintenance and produced sustained reductions in TAG and increases in HDL-C compared with the CHO diet
No significant differences were observed for weight , waist circumference , fat mass , blood lipids ( i.e. total cholesterol , LDL-cholesterol , HDL-cholesterol , triacylglycerols ) , C-reactive protein , diastolic and systolic blood pressure , fasting glucose and glycosylated hemoglobin .
Sensitivity analysis of high quality RCTs confirmed the data of the primary analyses , while exclusion of studies with diabetic subjects result ed in an additional benefit of high-protein diets with respect to a more marked increase in HDL-cholesterol .
Conclusion According to the present meta- analysis of long-term RCTs , high-protein diets exerted neither specific beneficial nor detrimental effects on outcome markers of obesity , cardiovascular disease or glycemic control .
Background Meta-analyses of short-term studies indicate favorable effects of higher protein vs. lower protein diets on health outcomes like adiposity or cardiovascular risk factors , but their long-term effects are unknown .