Effect of a high- protein diet on plasma inflammatory proteins in obese women

Obesity is an independent risk factor for cardiovascular diseases and diabetes. The abnormalities involved may be mediated by increased secretions of inflammatory proteins called adipocytokines by the adipose tissue. Thus, monitoring adipocytokines during weight loss could be helpful in progress evaluation of weight reduction programs. Since high-protein diets are considered diets of choice for weight reduction in some communities, their effectiveness should be re-evaluated. The objective of this study was to compare the effects of a standard-protein diet with a high-protein diet on weight loss and biochemical health indices, e.g., the blood lipid profile and plasma inflammatory proteins, in obese women. Twenty-eight 20-48 year-old obese women [BMI= 30-41 kg/m[2]] were divided into 2 groups. One group was assigned to a high-protein diet [HP, protein supplying 30% of energy] and one to a standard-protein diet [SP, protein supplying 15% of energy]. Anthropometric and biochemical variables were measured at the beginning and after 10 weeks. The magnitude of weight loss [6.0 +/- 2.3 kg on HP and 4.9 +/- 2.4 kg on SP; P = 0.43] and fat loss [4.6 +/- 2.1kg on HP and 3.9 +/- 2.0 kg on SP; P = 0.63] did not differ significantly between the 2 groups. Insulin sensitivity index improved more on the HP diet [P = 0.01]. The reduction in the serum triacylglycerol concentration was significant in both groups [HP, P= 0.005; SP, P = 0.03] without any diet effect. Total cholesterol, HDL-C and LDL-C did not change significantly in either group. On the other hand, plasma leptin decreased more on the HP than on the SP diet [diet effect; P<0.05]. No significant changes in adiponectin, TNF-a, IL-6 or log CRP were observed after weight loss, although there was an desirable trend in all these inflammatory proteins. The high-protein diet was more effective in lowering plasma leptin concentration and improving insulin sensitivity than the standard-protein diet. However, the magnitude of weight loss and changes in the serum lipid or plasma inflammatory protein levels did not differ significantly between the energy-restricted high-protein and standard-protein groups