Background – Although diets with increased protein to carbohydrate appear more effective for improving body composition and metabolic outcomes in women, they have been poorly studied in men.
Objective – Our study aimed to comprehensively assess the efficacy of a high protein low GI diet (HP) compared to a high carbohydrate low GI diet (HC) for weight loss in overweight/obese men. Design–Onehundredandtwentythreeoverweightmenaged49±9yandBMI34±6kg/m wererandomizedtoone of 2 isocaloric (7MJ) weight loss diets for 12 weeks. HP: (Protein:CHO:Fat;%Sat Fat = 35:40:25;8%) or HC (17:58:25;8%). Outcome measures were regional fat and lean loss as well as cardiovascular risk markers.
Outcome – Weight loss on both diets was similar; 8.9±4.2kg (mean±SD). Total abdominal fat mass loss was significantly greater on HP compared with HC even after controlling for baseline differences (HP -0.76±0.38 kg vs HC, -0.56±0.36 kg; P=0.02). Triglycerides (TG) fell by 0.45±0.70 mmol/L, LDL cholesterol by 0.48±0.66 mmol/L, blood pressure by 11/12±10/8mmHg and HDL cholesterol remained unchanged independent of diet composition. Glucose and insulin fell by 0.27±0.58mmol/L and 4±6mU/L respectively. CRP fell significantly only in those subjects with TG>2 mmol/L and on HP (P=0.03 time/diet/TG status interaction). Plasma folate increased 7% on both diets and homocysteine remained unchanged at 7.7 μmol/L. Plasma B12 increased significantly only on HP by 20% (P=0.027 for diet interaction).
Conclusion – Both high protein diets and high carbohydrate low GI diets are effective in improving cardiovascular risk in obese men but with some metabolic advantages on the higher protein pattern.