Exercise Effects on Insulin, Gut Peptides, and Appetite

Not Applicable

Completed

Brief Summary: Determine whether the mid-day suppression of hunger and amplified increase in the release of glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide 1 (GLP-1) following morning exercise is due to increased fat content of the diet per se or a combination of high fat diet after morning exercise. The action of gut peptides, particularly GLP-1, on gastric emptying is likely to be important in mediating its effects on postprandial appetite and glycemia (Nauck et al. 1997). Our hypothesis is that exercise amplifies gut peptide secretion when diet is enriched with fat, and that this stimulus suppresses the hunger sensation.

Detailed Description: 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.

Recruitment & Eligibility

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.

Arm && Interventions

Group	Intervention	Description
Sedentary-high-fat diet	Exercise and diets	Sedentary trial with two high-fat meals
Exercise-high-carbohydrate diet	Exercise and diets	Two bouts of exercise followed by a high-carbohydrate meal
Exercise-high-fat diet	Exercise and diets	Two bouts of exercise followed by a high-fat meal
Sedentary-high-carbohydrate diet	Exercise and diets	Sedentary trial with two high-carbohydrate meals

Primary Outcome Measures

Name	Time	Method
Plasma concentration of beta-hydroxybutyrate	36 hours	Changes in plasma concentration of beta-hydroxybutyrate to two bouts of exercise followed by either a high-carbohydrate or a high-fat meal
Plasma glucagon concentration	36 hours	Changes in plasma glucagon concentration to two bouts of exercise followed by either a high-carbohydrate or a high-fat meal
Plasma concentration of free fatty acids	36 hours	Changes in plasma concentration of free fatty acidsto two bouts of exercise followed by either a high-carbohydrate or a high-fat meal
daytime hourly appetite ratings	36 hours	Changes in daytime hourly appetite ratings to two bouts of exercise followed by either a high-carbohydrate or a high-fat meal
Plasma insulin concentration	36 hours	Change in plasma insulin to two bouts of exercise followed by a high-carbohydrate or a high fat diet
Plasma glucose concentration	36 hours	Changes in plasma glucose concentration to two bouts of exercise followed by either a high-carbohydrate or a high-fat meal
Plasma concentration of glucose-dependent insulinotropic peptide (GIP)	36 hours	Changes in plasma concentration of glucose-dependent insulinotropic peptide (GIP)to two bouts of exercise followed by either a high-carbohydrate or a high-fat meal

Secondary Outcome Measures

Name	Time	Method
Plasma concentrations of glucagon-like peptide-1 (GLP-1)	36 hours	Changes in plasma concentrations of glucagon-like peptide-1 (GLP-1)to two bouts of exercise followed by either a high-carbohydrate or a high-fat meal
Plasma concentrations of peptide tyrosine tyrosine (PYY)	36 hours	Changes in plasma concentrations of peptide tyrosine tyrosine (PYY) to two bouts of exercise followed by either a high-carbohydrate or a high-fat meal

Locations (1): Michigan Clinical Research Unit
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Ann Arbor, Michigan, United States