Relative Effects of Time-Restricted Eating, Energy-Restricted Eating, and Unrestricted Eating on Eating Patterns and Dietary Intake: Results From a Randomized Controlled Trial.

BackgroundTime-restricted eating (TRE) may be as effective as an energy-restricted (ER) diet for weight loss. However, little is known about the effects of TRE on eating patterns and dietary intake.ObjectiveThe aims of this study were to examine the relative effects of TRE, ER, and unrestricted eating (UE) diets on eating patterns and dietary intake.DesignThis study is a secondary analysis of data from a randomized controlled trial carried out between October 2020 and October 2023. Over this period, 88 participants were randomized to a TRE, ER, or UE diet group.Participants/settingAdults with obesity in the Minneapolis-Saint Paul, Minnesota, metropolitan area who completed study baseline and follow-up measures of dietary intake (n = 73).InterventionThe interventions were (1) TRE with an 8-hour self-chosen window with ad libitum diet; (2) ER diet with 15% reduction of energy intake; or (3) UE in which self-monitoring of food intake was encouraged with no specific change to eating recommended. The intervention period was 12 weeks.Main outcome measuresOutcomes included meals eaten and intake of vegetables, fruit, dairy, protein foods, grains, energy, added sugars, saturated fat, sodium, dietary fiber, and potassium.Statistical analysesMultivariate linear regression analyses were carried out to compare the change in food and nutrient intake between experimental groups. Logistic mixed-effects models were constructed to examine the change in meals eaten.ResultsThe TRE group ate fewer daily meals at end-intervention (-1.1 meals/day; 95% confidence interval [CI], -1.6, -0.7) compared with baseline, whereas the ER and UE groups did not experience a change in eating occasions. Those in the TRE group were less likely to report eating breakfast during end-intervention compared with baseline (odds ratio [OR], 0.13; 95% CI, 0.05, 0.33), whereas no statistically significant change in behavior was identified for the ER (OR, 1.02; 95% CI, 0.41, 2.55) or UE (OR, 0.68; 95% CI, 0.28, 1.68) groups. Between baseline and end-intervention those in the TRE group had a decrease in intake of energy (-469 kcal/day; 95% CI, -681, -257), saturated fat (-8.5 g/day; 95% CI, -12.9, -4.1), potassium (-496 mg/day; 95% CI, -729, -263), and total (-1.7 ounce equivalents/day; 95% CI, -2.9, -0.6) and refined grains (-1.6 ounce equivalents; 95% CI, -2.6, -0.6). These changes were more marked compared with changes in the UE group. There were no statistically significant differences found between those in the TRE and ER groups.ConclusionsFindings suggest that TRE with an 8-hour window and ad libitum intake may have similar effects on food and nutrient intake as an energy-restricted diet.