The overall goal is to examine the efficacy of a circadian intervention in people with overweight and obesity and habitual short sleep duration (HSSD). Participants will undergo a randomized controlled trial, with circadian intervention and control (healthy lifestyle) groups. The circadian intervention is designed to reduce nighttime light exposure and after-dinner snack food intake. Alternatively, the control group will receive basic health information (e.g., physical activity, goal setting, and nutrition when eating out).

The study is a randomized controlled trial with control and circadian intervention groups. Group allocation will be blinded to research staff and participants until the conclusion of the baseline segment. The circadian intervention group will receive counseling and instruction to reduce evening and nighttime light exposure, increase morning room light and sunlight exposure, and complete all food consumption at least 4 hours before bedtime. Participants randomized to control will maintain their habitual food intake and sleep habits in their home environment for ~8 weeks. Both groups will have equal contact time with the study team.

Prior to enrollment participants will complete an clinical overnight sleep disorders screening. Baseline consists of an ~1-week ambulatory real-world monitoring segment. Following baseline participants will be randomized to the control or intervention groups for the 8 week experimental segment. Throughout the study sleep duration will be monitored using an actiwatch wrist-device and a daily electronic sleep log. At the end of the baseline and experimental segments participants will complete overnight laboratory visits to assess insulin sensitivity and circadian timing by oral glucose tolerance test and dim light melatonin onset, respectively.

Inclusion Criteria:

1. Age: 18-45 years old; equal numbers of men and women
2. Body mass index (BMI): 25.0-34.9 kg/m2,
3. Sleep Habits: habitual self-reported average total sleep time (TST) <6.5 hours per night for prior 6 months

Exclusion Criteria:

1. Clinically diagnosed sleep disorder or major psychiatric illness
2. Evidence of significant organ dysfunction or disease (e.g., diagnosed diabetes, cardiovascular disease, or kidney disease)
3. Use of prescription drugs or substances known to influence sleep or glucose metabolism
4. Shift-work: current or history of within last year
5. Weight change: >10% of body weight over prior six months
6. Experiencing menopause or post-menopausal
7. Current enrollment in weight loss or physical activity program like the Diabetes Prevention Program
8. Currently pregnant or planning to become pregnant, or currently lactating.
9. Currently smoking
10. Alcohol intake >3 drinks per day or >14 drinks per week

Group allocation will be blinded to research staff and participants until the conclusion of the baseline segment.