Exercise Training and Dietary Glycemic Load May Have Synergistic Effects on Insulin Resistance in Older Obese Adults

• Published in: Annals of nutrition and metabolism 2009-01, Vol.55 (4), p.326-333
• Main Authors: Kirwan, John P., Barkoukis, Hope, Brooks, Latina M., Marchetti, Christine M., Stetzer, Bradley P., Gonzalez, Frank
• Format: Article
• Language: English
• Subjects: Aged; blood glucose; blood lipids; Body Mass Index; Body weight; carbohydrate loading; Combined Modality Therapy - statistics & numerical data; Diabetes Mellitus - prevention & control; Diet; Dietary Carbohydrates; elderly; elderly nutrition; energy intake; Exercise; Exercise - physiology; Female; Glucose Clamp Technique; glucose tolerance; Glycemic Index; Heart rate; Humans; Insulin; Insulin resistance; Insulin Resistance - physiology; Lipids - blood; Load distribution; Male; Metabolic disorders; noninsulin-dependent diabetes mellitus; Nutrition research; Obesity; Obesity - complications; Obesity - physiopathology; Obesity - therapy; Older people; Original Paper; overweight; Oxygen Consumption; Physical Fitness; Physical training; randomized clinical trials; senescence; Synergistic effect
• ISSN: 0250-6807; 1421-9697
• DOI: 10.1159/000248991

Background/Aims: The aim of this study was to assess the combined effects of exercise and dietary glycemic load on insulin resistance in older obese adults. Methods: Eleven men and women (62 ± 2 years; 97.6 ± 4.8 kg; body mass index 33.2 ± 2.0) participated in a 12-week supervised exercise program, 5 days/week, for about 1 h/day, at 80-85% of maximum heart rate. Dietary glycemic load was calculated from dietary intake records. Insulin resistance was determined using the euglycemic (5.0 mM) hyperinsulinemic (40 mU/m2/min) clamp. Results: The intervention improved insulin sensitivity (2.37 ± 0.37 to 3.28 ± 0.52 mg/kg/min, p < 0.004), increased VO2max (p < 0.009), and decreased body weight (p < 0.009). Despite similar caloric intakes (1,816 ± 128 vs. 1,610 ± 100 kcal/day), dietary glycemic load trended towards a decrease during the study (140 ± 10 g before, vs. 115 ± 8 g during, p < 0.04). The change in insulin sensitivity correlated with the change in glycemic load (r = 0.84, p < 0.009). Four subjects reduced their glycemic load by 61 ± 8%, and had significantly greater increases in insulin sensitivity (78 ± 11 vs. 23 ± 8%, p < 0.003), and decreases in body weight (p < 0.004) and plasma triglycerides (p < 0.04) compared to the rest of the group. Conclusion: The data suggest that combining a low-glycemic diet with exercise may provide an alternative and more effective treatment for insulin resistance in older obese adults.