Time Restricted Feeding (4-hour Versus 6-hour) for Weight Loss in Obese Adults

Modest weight loss of 5-10% is sufficient to reduce metabolic disease risk in obese
individuals. The first line of therapy prescribed for weight loss is daily calorie
restriction (CR; 25% restriction every day). However, adherence to CR greatly diminishes
after 4-6 weeks, due to subject frustration with constantly having to count calories and
never being able to eat freely. In light of these issues with CR, another approach that
limits timing of food intake, instead of number of calories consumed, has been developed.
This strategy is termed time restricted feeding (TRF), and involves confining the period of
food intake to 8 h/d (10 am to 6 pm) without calorie counting. Preliminary findings of 8-h
TRF demonstrate modest weight loss and blood pressure reductions after 12 weeks. What remains
unknown however, is whether shorter feeding windows during TRF (such as 4-h or 6-h feeding
windows) can produce even greater weight loss in obese adults. Also of interest, is the
impact of these shorter feeding windows on metabolic disease risk indicators (such as plasma
lipids, blood pressure, and insulin resistance), sleep, and inflammatory markers.
Accordingly, the aims of this proposal are: AIM 1: To compare the effects of 4-h versus 6-h
time restricted feeding (TRF) on body weight and body composition in adults with obesity; AIM
2: To compare the effects of 4-h versus 6-h TRF on metabolic disease risk factors in adults
with obesity; AIM 3: To compare the effects of 4-h versus 6-h TRF on sleep quality and
duration in adults with obesity; AIM 4: To compare the effects of 4-h versus 6-h TRF on
inflammatory markers. To test the study objectives, a 10-week randomized, controlled,
parallel-arm trial, divided into 2 consecutive periods: (1) 2-week baseline period; and (2)
8-week TRF weight loss period, will be implemented. Obese subjects (n = 150) will be
randomized to 1 of 3 groups: (1) 4-h TRF (n = 50), (2) 6-h TRF (n = 50), or a no-intervention
control group (n=50). This study will be the first randomized controlled trial of 4-h versus
6-h TRF, and will show that the 4-h TRF diet produces greater improvements in body weight,
body composition, metabolic disease risk factors, sleep, and inflammation when compared to
the 6-h TRF diet.

Inclusion Criteria:

- Male or female;

- body mass index (BMI) between 30.0 and 49.9 kg/m2;

- age between 18 and 65 years; sedentary (light exercise less than 1 h per week) or
moderately active (moderate exercise 1 to 2 h per week);

- weight stable for >3 months prior to the beginning of the study (gain or loss <4 kg);

- able to give written informed consent

Exclusion Criteria:

- Smoker; diabetic;

- history of alcohol dependance (score >20 from Alcohol and Health Questionnaire 8);

- taking weight loss medications;

- taking medication that requires eating food before (or with) the medication; history
of eating disorders;

- night-shift workers;

- perimenopausal;

- pregnant women