The Influence of Diet During and After Exercise on Metabolic Benefits of Exercise in Overweight Adults

Participants: Women (n=24; 18-55 y) with a BMI > 25 and < 35 kg·m-2 who are sedentary to moderately active were recruited to participate. Research Design: This study was a randomized, counter-balanced, cross-over clinical trial consisting of three experimental conditions in which each participant served as her/his own control. Assessments of health history, physical activity (to confirm that participants were physically inactive), anthropometrics, resting metabolic rate, and aerobic capacity were made during an initial laboratory visit. Participants performed three different study conditions, typically separated by one week, thus women were not tested in a specific menstrual cycle phase. Participants recorded their diet the day before and the morning of the first condition and replicated this for the second and third conditions. On the study days, participants consumed their breakfast prior to 9:00 AM and arrived in the lab at 11 AM. The three conditions were performed in randomized order. In the control condition (CON), participants rested quietly for 1 hour. In the remaining two conditions, participants performed 45 minutes of treadmill exercise at 11 AM. Following the rest or exercise period, subjects were provided energy balanced diets. Total energy intake was balanced across exercise conditions and appropriately adjusted for the lack of exercise in the CON condition. At 7 AM on the following morning, following an overnight fast, an oral glucose tolerance test (OGTT) was performed. Measurements were made to determine fasting glucose, insulin and lipid panel, 2-hour OGTT glucose, insulin sensitivity (SI OGTT), early (0-30 min) and late (30-120 min) glucose stimulated insulin secretion (GSIS) based on c-peptide concentrations. Indirect calorimetry was also performed to determine resting carbohydrate and fat oxidation and metabolic flexibility, defined as the change in respiratory exchange ration (RER) during the OGTT. Interleukin-6, tumor necrosis factor-alpha, and reactive oxygen species were measure before, 60, and 120 minutes during the OGTT to assess the inflammation response.