The primary aim of this study is to evaluate if a single bout of AM vs PM resistance exercise has different effects on insulin sensitivity and sleep. A randomized cross-over trial be used to compare resistance exercise at two different times of the day. Each condition will take place in a laboratory setting. Each condition will consist of exercise, overnight sleep, and oral glucose tolerance tests the following day. The AM exercise will occur ~1.5 hours after habitual wake, and PM exercise will occur ~11 hours after habitual wake. After a 2-6 week washout, participants will complete the other condition. The hypothesis is that PM exercise will be more beneficial than AM exercise in improving insulin sensitivity. This study could identify if there is a better time of day to perform resistance exercise to decrease risk of developing Type 2 Diabetes Mellitus.

Inclusion Criteria:

• Men and women, all ethnicities, aged 50-74 years
• BMI ≥25 kg/m² and <45 kg/m²
• Weight stable (less than 5% change in the past 6 months)
• Generally healthy individuals
• Not meeting recommended activity guidelines for aerobic or resistance exercise

Exclusion Criteria:

• Uncontrolled cardiovascular, metabolic, renal, or pulmonary disease
• Cancer treatment in the past 5 years
• Untreated thyroid disease or other medical conditions affecting weight or energy metabolism
• Current use of weight loss medication or other medications likely to impact energy balance
• Bariatric surgery or extensive bowel resection in the past 2 years
• Current or recent history (past 2 years) of eating disorder
• Diagnosis of insomnia, sleep apnea, or other sleep and circadian disorders
• Non-English speaking
• HbA1c >6.5%