(12-01-06) Comparison of 4 ad libitum weight loss diets of varying glycemic load on cardiovascular risk factors.

McMillan-Price J, Petocz P, Atkinson F, O'neill K, Samman S, Steinbeck K, Caterson I, Brand-Miller J.

Human Nutrition Unit, University of Sydney, NSW.

Background - Compared with conventional low fat diets, high-protein and low-glycemic index (GI) diets have been associated with greater rate of weight loss. While both methods reduce dietary glycemic load (GL), the effects on cardiovascular risk may differ. Objective - To evaluate the effects of 4 diets varying in GL, GI and protein on lipid and glucose metabolism. Design - A 12-week randomised trial of 4 ad libitum diets: diet 1 was a high carbohydrate, high GI diet (HGI), diet 2 was similarly high in carbohydrate but low GI (LGI), diets 3 and 4 replaced some of the carbohydrate with protein, specifically from lean red meat, and included carbohydrate from either high or low GI foods (HP/HGI and HP/LGI respectively). The diets were similar in fat (30% energy) and type of fat. All key foods and some pre-prepared meals were provided on a weekly basis to assist compliance. Fasting blood samples were taken 0, 6 and 13 weeks. Outcomes - In total, 129 subjects were recruited and 116 completed the intervention. Changes in weight and body composition were reported previously. In the primary intention-to-treat analysis, total cholesterol and LDL-cholesterol changes showed significant differences among the 4 diets (P = 0.04 and 0.019 respectively). Despite similar weight loss, total and LDL-cholesterol rose by +5% and +8% respectively on the HP/HGI diet and fell by -4% and -6% respectively on the LGI diet (p = 0.033 and 0.013 for total and LDL-cholesterol respectively). Overall, there was a significant effect of GI, but not protein content, on change in total cholesterol (P = 0.019) and LDL cholesterol (P = 0.009). HDL-cholesterol rose and triglyceride concentrations fell in all groups with no differences among the four diets. Conclusions - Reduced GL diets have varying effects on cardiovascular risk factors. Low GI carbohydrate foods may be more important in high protein diets because of their capacity to attenuate undesirable changes in lipid metabolism.

Asia Pac J Clin Nutr. 2005;14 Suppl:S51.

PMID: 16326510 [PubMed - in process]

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