A study, reported in the American Journal of Clinical Nutrition (June 2005), compared the effects of a high-protein and a high-carbohydrate diet on weight loss, blood lipids, bone turnover, and renal function in overweight women. Overall, both diets led to about a 16-pound weight loss during the 12 week study. Both diets also led to significant improvements in markers for cardiovascular risk.
The high-protein diet, however, was associated with better B12 status, greater improvements in hemoglobin, and greater reductions in triacylglycerol concentrations. High triacylglycerol concentrations is one of the key markers of insulin resistance.
The researchers did a subgroup analysis to see if insulin resistance predicted how the women responded to the diets. Women who had high levels of triacylglycerol at the start of the study lost 50% more total fat on the high-protein diet than on the high-carbohydrate diet.