Inflammation, insulin, and glucose differences between high and low glycemic index diets following downhill running in overweight and obese women
McNulty, Katherine Angela Maureen.
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Low-grade chronic inflammation is associated with excess adipose tissue, and often precedes chronic disease. Overweight and obese individuals lose the ability to control inflammation as percent body fat increases, likely linked to inefficient carbohydrate oxidation that amplifies inflammation. Little is known about how the quality of carbohydrates influences inflammation of muscle in this population. The purpose of this study was to determine whether there are differences in inflammation and glucose metabolism between low glycemic index (LGI) and high glycemic index (HGI) diets following downhill running in overweight and obese women. This study was a pre-post design in which overweight and obese women (n = 20) were placed in matched pairs for percentage body fat, each receiving an isomacronutrient LGI or HGI diet. Participants completed a downhill run at heart rates at 65% predicted maximal oxygen consumption (VO 2max) until 15% loss of isometric force of the hip and knee extensors, or volition fatigue, was achieved. Participants ate their prescribed diet for 24 h post exercise. Glucose, insulin, creatine kinase (CK), C-reactive protein, tumor necrosis factor-alpha, and interleukin-6 were measured pre-exercise, 0, 24, and 48 h post-exercise. Isometric force and muscle tenderness were measured when blood was collected. Serum CK changed significantly over time (p < 0.001), with the peak at 24 h in the HGI group, and at 48 h in the LGI group. Isometric force decreased most at 24 h for the HGI group, and at 48 h for the LGI group, with significant differences occurring over time (p = 0.01), and a significant time/diet interaction (p = 0.02). No significant changes were seen in any of the inflammatory variables for diet or time, with the exception of the expected increase in IL-6 immediately post-exercise. There was a significant (p = 0.035) difference in delta insulin between groups. Delta IR also changed significantly over time between groups (p = 0.044). We conclude that while inflammation was not different between groups, a LGI diet following downhill running results in an acute improvement in insulin and IR in overweight and obese women.