The effect of diets high in protein or carbohydrate on inflammatory markers in overweight subjects

AIM: Increased levels of inflammatory markers have been associated with weight gain and cardiovascular disease. The aim of the present study was to investigate the effect of diets high in either carbohydrate or protein on the inflammatory markers C-reactive protein (CRP), haptoglobin and transferrin in plasma after weight loss. METHODS: Fifty overweight subjects [age: 18-56 years, body mass index (BMI): 27-34] were randomly assigned to an ad libitum, fat-reduced diet (30% of energy, E%), either high in protein and low in carbohydrate (25 E and 45 E% respectively) or high in carbohydrate and low in protein (58 E and 12 E% respectively), during 6 months of strictly controlled dietary intervention with dietary counselling. RESULTS: An average reduction of 25% in CRP and an average increase of 20% in haptoglobin and transferrin were seen in both groups, however, these changes were not significant. In cross-sectional analyses after the intervention CRP was associated with fat mass (r = 0.323, p = 0.03), and the changes in CRP were associated with various indices of body fatness (Deltabody weight r = 0.346, p = 0.02). Changes in body fatness were positively associated with Deltatransferrin (r = 0.344, p = 0.02) and nearly significantly associated with Deltahaptoglobin (r = 0.271, p = 0.07) after 6 months. Multiple regression analysis showed no associations between dietary protein and carbohydrate content and serum CRP, haptoglobin or transferrin concentrations, and this remained unaltered after adjustment for weight change. CONCLUSION: Dietary carbohydrate/protein ratio has no effect on inflammatory markers, but the study confirmed that body fatness is positively associated with levels of serum CRP.