Metabolic Adaptations to Chronic and Acute Exercise in Overweight Adults (ATX-Study)

Subjects will be asked to complete the Substrate Metabolism Laboratory General Screening Questionnaire and American Heart Association Health/Fitness Questionnaire to determine if they are eligible to complete the preliminary testing procedures. If eligible, subjects will be asked to visit the Substrate Metabolism Laboratory to participate in the preliminary testing procedures (listed below) before participating in the experimental trial.

PRELIMINARY TESTING PROCEDURES:

• Blood pressure, height and weight measurements
• Body Composition Assessment (~20 min)
• Exercise Fitness Test (~10 min)
• Resting Metabolic Rate (RMR) measurement (~30 min)
• 3 hour Oral Glucose Tolerance Test (OGTT)

EXPERIMENTAL TRIAL:

The evening before the experimental trial, subjects will eat a standardized dinner meal and snack. The meal and snack must be eaten at specific times as indicated by the research staff. After eating the snack, subjects will need to fast (no food or beverages - besides water) overnight.

Participants who exercise regularly will be instructed to exercise exactly 3 days before the experimental trial, and then abstain from their exercise training program until after the study is complete.

In the morning, subjects will return to the Substrate Metabolism Laboratory. The research team will collect a blood sample from the subject's hand or forearm and a small sample of fat tissue in the subject's abdomen with a needle. Next, subjects will exercise on a treadmill at a moderate intensity for about 1 hour. Immediately after exercising the research team will collect a second blood sample. Subjects will remain in the laboratory for 1 hour after exercising, and then the research team will collect another blood and fat tissue sample. Upon completion of the experimental trial, subjects will be provided a snack before leaving the laboratory.

Inclusion criteria

• Age: 18-40
• Body Mass Index: 25-35 kg/m2
• Regular exercisers: (≥4 days/wk of aerobic exercise; 30-60min/session at moderate and vigorous intensities)
• Non-exercisers: no regularly planned exercise/physical activity
• Women must have regularly occurring menses and must be premenopausal

Exclusion criteria

• Blood pressure > 140/90 mm Hg
• Pregnant or lactating
• Evidence/history of cardiovascular or metabolic disease
• Medications known to affect lipid or glucose metabolism