Exercise Effects on Insulin, Gut Peptides, and Appetite

Specific aim: Determine whether a change in macronutrient composition from 60% carbohydrate and 25% fat to 30% carbohydrate and 45% fat is responsible by itself for suppression of hunger and increased secretory response of glucose-dependent insulinotropic hormone (GIP) and glucagon-like peptide-1 (GLP-1), or whether these changes depend on preceding exercise. We will measure (a) concentrations of plasma GIP and GLP-1 by chemiluminescent multiplex assay, (b) concentrations of plasma ancetaminophen to assess the gastric emptying rate, (c) concentrations of plasma insulin, and glucagon by radioimmunoassay, and glucose, ketone bodies, and free fatty acids with appropriate spectrophotometric methods, (d) hourly appetite responses with visual analog scale under two conditions: sedentary (SED) and exercise (EX).

Hypothesis: Hunger suppression and secretion of GIP and GLP-1 after the morning meal will be greater with slower gastric emptying rate when a meal consisting of 45% fat and 30% carbohydrate follows three hours after a 2-hour bout of moderate-intensity exercise than in the absence of exercise.

Inclusion criteria

• Postmenopausal status
• Age 50 to 65 years
• BMI between 20 and 30 kg/m2.
• Good health status (normotensive, fasting glucose < 100 mg/dl, , hematocrit > 32%, hemoglobin >12 mg/dl)
• Absence of restricted food intake
• Absence of endocrine and metabolic disorders requiring medication other than hormonally corrected hypothyroidism
• Absence of musculoskeletal disabilities that would prevent walking

Exclusion criteria

• Presence of endocrine and metabolic disease requiring medication, other than hormonally corrected hypothyroidism
• Presence of musculoskeletal disabilities that would prevent walking
• Smoking
• Active dieting
• Absence of listed inclusion criteria
• Unwillingness to follow study protocol.