Time restricted feeding (TRF) is a form of intermittent fasting that has gained substantial popularity
over recent years as a weight loss regimen. Despite its growing popularity, very few studies have
examined the weight loss efficacy of this diet. TRF involves eating within a specific window of time
each day, and water fasting for the rest of the day. The goal of this study was to compare the effects of
a 4-h TRF versus 6-h TRF on body weight, metabolic disease risk factors, inflammation, and sleep, in
adults with obesity. Subjects with obesity (n = 58) were randomized to 1 of 3 groups: 1) 4-h TRF (ad
libitum feeding between 3pm to 7pm, water fasting between 7pm to 3pm), 2) 6-TRF (ad libitum
feeding between 1pm to 7pm, water fasting between 7pm to 1pm), or 3) control group (usual diet with
no meal timing restrictions) for 8 weeks. Results from this study show that 8 weeks of 4-h and 6-h TRF
decreases body weight by -3.2% and -3.2%, respectively, relative to controls. Subjects were adherent
to the prescribed eating window on 6.2 days per week, and this level of adherence remained constant
throughout the 8-week trial. Our findings also indicate that reducing the daily eating window to either
4-h or a 6-h decreases caloric intake by ~550 kcal/d, without intentional calorie counting. Both TRF
interventions produced significant reductions in fasting insulin, HOMA-IR (measurement of insulin
resistance) and oxidative stress, versus controls. However, other metabolic disease risk parameters
such as plasma lipids, blood pressure, and inflammation, remained unchanged. As for sleep, sleep
quality and duration remained unchanged in all groups. Our results also suggest that TRF is a safe diet
therapy that does not induce any significant adverse effects. These data offer promise for the use of
shorter (4-h and 6-h) eating windows as safe and effective weight loss regimens in adults with obesity.
However, longer-term, larger-scale randomized controlled trials will be required before solid
conclusions can be reached
