Effects of a high-protein, low-glycemic-index diet on body weight and waist circumference in late postmenopausal women: a randomized controlled trial.

Objective: To describe the secondary outcomes (weight loss, waist circumference [WC], and glycolipid profile) of a previous randomized controlled trial designed to investigate the impact of a high-protein, low-glycemic-index (GI) diet on lean body mass in late postmenopausal women.

Subjects and methods: A total of 26 healthy women aged ≥ 65 years and with a mean body mass index (BMI) of 26.1 ± 3.5 kg/m² were randomly assigned to follow a low-GI diet (GI < 55) with protein consumption at the current recommended dietary allowance (RDA, 0.8 g/kg body weight) or twice the RDA (2RDA, 1.6 g/kg body weight). Changes in body weight, BMI, WC, glucose, homeostasis model assessment of insulin resistance (HOMA-IR), total cholesterol, and triglycerides were assessed at 3- and 6-month of follow-up in all participants. An intention-to-treat analysis was performed using a linear mixed model.

Results: Weight loss (mean change -1.7 kg, 95% confidence interval [CI] -2.8 to -0.5 kg, p = 0.004) was observed at 6 months, with no significant difference between the RDA and 2RDA groups. An overall significant WC decrease was observed at 6 months in all participants (mean change -3.8 cm, 95% CI -5.5 to -2.1 cm, p < 0.001), with no differences between groups. The glycolipid profile remained unchanged after 6 months of dietary intervention.

Conclusion: Increasing protein intake did not lead to greater weight loss or reduction in WC in a sample of healthy postmenopausal women following a low-GI diet for 6 months.