Daily Eating Patterns for Total Health Study

The goal of this randomized controlled trial is to learn how the time of day when calories are eaten affects weight loss in the long-term (12 months). The main aims are to learn:

1. The influence of time-based energy intake goals on longer-term weight loss.
2. The influence of time-based energy intake goals on eating temporal patterns, sleep regularity, and appetite regulation.

Researchers will compare whether goals to eat most of a person's calories in the morning or evening work to treat obesity.

Participants will:

1. Eat a reduced-calorie, low-fat diet (some participants will have goals to eat their calories at certain times of day based on their group)
2. Be physically active at least 200 minutes
3. Receive a cognitive behavioral intervention

This randomized controlled trial investigates the longer-term (12 months) effect of time-based energy intake goals on weight loss. It also explores whether enhanced appetite regulation is a mediator of the relationship and if chronotype moderates the effect. Adults with overweight or obesity are randomly assigned to one of three, 12-month lifestyle interventions: 1) Morning; 2) Evening; or 3) Standard. All conditions receive a reduced-energy, low-fat dietary prescription (1200-1500 kcal/d, \< 30% energy from fat), physical activity goals (\> 200 min/wk of moderate- to vigorous-intensity physical activity \[MVPA\]) and a cognitive behavioral intervention. To minimize the effect of other eating temporal variables on outcomes, guidance on the eating window length and the number of eating occasions in the day are consistent across all three conditions. Thus, the three conditions are instructed to have their first eating occasion \< 60 minutes of awakening, and eat their three meals and one snack within a 12-hr eating window. Morning group has time-based energy intake goals of 70% of kcal within the first 6 hrs of the eating window and 30% of kcal within the last 6 hrs of the eating window (a morning-loaded energy distribution). Evening group has the opposite time-based energy intake goals (an afternoon/evening-loaded energy distribution). Standard group receives no guidance on energy intake distribution (standard lifestyle intervention). Assessments occur at 0, 3, 6, and 12 months on anthropometrics, diet (24-hr recalls with time-stamped digital images verifying timing of intake, combined with continuous blood glucose monitoring \[CGM\] to objectively assess for length of the eating window and number of eating occasions), sleep regularity (actigraphy supported by sleep logs collected via ecological momentary assessment \[EMA\] using smartphones), appetite regulation assessed via EMA using smartphones, chronotype (self-reported midpoint of sleep on work-free days), and MVPA (actigraphy).

The primary aims are to determine:

1. The influence of time-based energy intake goals on longer-term weight loss.
2. The influence of time-based energy intake goals on eating temporal patterns, sleep regularity, and appetite regulation.

The exploratory aims are to consider:

1. If appetite regulation mediates the relationship between time-based energy intake goals and weight loss.
2. The moderating effect of chronotype on weight loss and changes in eating temporal patterns, sleep regularity, and appetite regulation in the three conditions.

Eligibility Criteria:
Inclusion Criteria:

* Body mass index (BMI) between 27 and 45 kg/m2.

Exclusion Criteria:

* Report not regularly (\>/= 5 days/wk) consuming energy (\>/= 100 kcal) prior to 12 pm, and not being able to consume energy every day (\>/= 50 kcal) within one hour of awakening.
* Report taking sleep medication or not regularly (\>/= 5 nights/wk) getting at least 6 hrs of total sleep.
* Report being a shift workers/alternative shift workers that work outside of 7 am and 7 pm.
* Report being diagnosed with type 1, or type 2 diabetes and taking medication that requires eating to occur at certain time periods.
* Report a heart condition, chest pain during periods of activity or rest, or loss of consciousness on the Physical Activity Readiness Questionnaire (PAR-Q). Individuals reporting joint problems, prescription medication usage, or other medical conditions that could limit exercise will be required to obtain written physician consent to participate.
* Report being unable to walk for 2 blocks (1/4 mile) without stopping.
* Report major psychiatric diseases or organic brain syndromes.
* Report currently participating in a weight loss program and/or taking weight loss or appetite regulation medication or lost \>/= 5% of body weight during the past 6 months.
* Report having bariatric surgery for weight loss/planning to have bariatric surgery in the next 12 months.
* Report being pregnant, lactating, \< 6 months post-partum or plan to become pregnant (next 12 months).
* Report planning to move outside of the metropolitan area within the time frame of the investigation.
* Do not have daily access to PC with internet or smartphones (needed for self-monitoring).