Timing Meals or Cutting Calories: Which Is Better?

TOPLINE:

A clinical trial comparing time-restricted eating (TRE), caloric restriction, and unrestricted eating for 12 weeks showed that TRE shortened eating windows to 9.8 hours but had no significant advantages in weight loss or improvements in metabolic measures.

METHODOLOGY:

• TRE, which restricts the consumption of food to a 4- to 12-hour window, simplifies dieting and may improve metabolism through extended fasting, regardless of weight loss.
• Researchers conducted a 12-week clinical trial to compare the effects of self-selected 8-hour TRE, 15% caloric restriction, and unrestricted eating on weight, body composition, caloric intake, glycemic measures, and metabolic flexibility in 88 patients with obesity and without diabetes (mean age, 43.2 years; mean body mass index, 36.2; 54.5% women; 87.5% White).
• Participants were required to self-report waking times between 5 AM and 9 AM, a sleep duration of 6-9 hours, and stable weight ±5 lb for more than 3 months prior to enrollment.
• They also recorded all their oral intake, except for water and medications.
• The primary outcome was the absolute change in weight; the secondary outcomes included the change in body composition (assessed using dual-energy x-ray absorptiometry/MRI), caloric intake, and metabolic flexibility.

TAKEAWAY:

• The final eating window was lowest for TRE (9.8 hours; 95% CI, 9.0-10.6) and comparable for caloric restriction (12.9 hours; 95% CI, 11.9-13.9) and unrestricted eating (11.8 hours; 95% CI, 11.0-12.7).
• Weight changes were not significantly different between TRE (P = .53) and caloric restriction (P = .18) compared with unrestricted eating.
• TRE demonstrated lower metabolic flexibility than caloric restriction (−0.041; 95% CI, −0.080 to −0.002); neither group showed differences in resting energy expenditure, lipid profile, or glycemic measures.
• A reduction in the eating window was correlated with a decrease in caloric intake and visceral fat.

IN PRACTICE:

“[The study finding] suggests that extending TRE [time-restricted eating] beyond 12 weeks may yield benefits,” the authors wrote.

SOURCE:

This study was led by Niki Oldenburg, Department of Medicine, University of Minnesota, Minneapolis. It was published online in Obesity.

LIMITATIONS:

This study required consistent use of the myCircadianClock app before randomization, potentially introducing selection bias by favoring participants with high logging adherence and mobile technology skills. Although the TRE group was asked to maintain an 8-hour eating window, the achieved window was approximately 9-10 hours. The 12-week study duration may have limited insights into long-term metabolic adaptations. The caloric reduction group achieved a reduction of approximately 9% instead of the targeted 15%, which may have contributed to the null findings among the groups.

DISCLOSURES:

This study received support from the University of Minnesota’s Clinical and Translational Science Award, National Institutes of Health, the Robert Wood Johnson Foundation, and Dexcom, Inc. (product support only). One author reported receiving royalty for authoring a book titled The Circadian Code, which recommends TRE.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.