Graded Doses of Exercise and Insulin Resistance in Nondiabetic Post-Menopausal Women

Abstract

Moderate-intensity aerobic exercise has been shown to be effective in modulating insulin resistance (IR) in diabetic populations; however, the effect of graded doses of exercise on IR in nondiabetic populations is unclear. PURPOSE: To examine the effects of graded exercise doses on fasting insulin, glucose and HOMA-IR (homeostasis model of assessment of IR) in nondiabetic women in the DREW (Dose Response to Exercise in Women Aged 45–75y) study. METHODS: Data from 374 previously sedentary, overweight (BMI 25–40 kg/m2), nondiabetic (fasting glucose <126 mg/dL) post-menopausal women with elevated BP (SBP 120–159 mm Hg, DBP ≤99 mm Hg) was used for analysis. Participants were randomized into a control group (A, n = 83) or 1 of 3 exercising groups: B) low dose (4 kcals/kg/week-KKW, n = 123), C) moderate dose (8 KKW, n = 80), or D) high dose (12 KKW, n = 88). Participants in the exercise groups completed 3–5 exercise sessions/ week at a HR associated with 50% VO2peak for 6 months. Fasting blood samples were obtained at baseline and post-intervention, analyzed for glucose and insulin levels, and HOMA was calculated [(insulin (μU/mL) X glucose (mM))/22.5]. The distribution of insulin and HOMA values were skewed and, thus, logarithmically transformed to normalize distribution of the residuals. Post-intervention log insulin, glucose and log HOMA were compared across groups using the SAS general linear model after adjustment for age and baseline values. RESULTS: Post-intervention fasting glucose was significantly (P < 0.01) lower for all exercise groups (94 ±0.6, 93 ±0.8, and 92 ± 0.8 mg/dL for B, C and D) versus controls (96 ± 0.8). Insulin levels were significantly (P < 0.04) lower in the high dose group (9.7 ± 1.0) and marginally lower (P < 0.06) in the moderate dose group (9.8 ± 1.0 μU/mL) relative to controls (10.9 ± 1.0) following intervention. Post-intervention HOMA was significantly lower in the moderate (P < 0.03) and high dose (P < 0.02) groups (2.2 ±1.0 and 2.2 ±1.0 Units) versus controls (2.6 ± 1.0). The trend across groups was significant for glucose, insulin and HOMA (P < 0.0001). CONCLUSIONS: Moderate-intensity aerobic exercise, specifically at or above doses recommended by the U.S. Surgeon General (8 KKW), improves IR in nondiabetic post-menopausal women. Supported by NIH grant HL66262 and equipment grants from Life Fitness.