Time-restricted eating starting early in the morning offers benefits

Key takeaways

• Choosing an 8-hour eating window that starts at 7 a.m. is more effective for weight loss than a typical 12-hour eating schedule.
• The intervention could potentially be used to treat obesity and hypertension.
• People who practiced time-restricted eating starting early in the morning also saw benefits for their mood.

When practicing a form of intermittent fasting — time-restricted eating — starting earlier in the day may be more effective for weight loss than typical eating habits, according to researchers.

Humaira Jamshed, PhD, an assistant professor of integrated sciences and mathematics at Habib University in Karachi, Pakistan, and colleagues sought to understand if the time in which one practices time-restricted eating influences weight loss and other outcomes. They found that, compared with normal eating over a period of 12 or more hours, time-restricted eating starting earlier in the day (eTRE) is more effective for both weight loss and lowered diastolic BP.

The intervention, they wrote, “may therefore be an effective treatment for both obesity and hypertension” — findings that align with previous research that has also linked intermittent fasting to weight loss and benefits for patients with obesity and insulin resistance.

In the randomized clinical trial, published in JAMA Internal Medicine, 90 people — 80% of whom were female — received an energy restriction weight-loss treatment and were randomly assigned to a control group or eTRE. The energy restriction weight-loss treatment included one-on-one counseling with a dietician, in which the participants were instructed to exercise between 75 and 150 minutes per week and follow a diet that is 500 kcal per day below their resting energy expenditure.

Those in the control group were able to choose a period of 12 or more hours to eat, mimicking average meal timing habits in the United States, and those in the eTRE group ate between 7 a.m. and 3 p.m. Adherence rates were good, the researchers wrote, noting that both groups kept to their diets at least 6 days per week and ate within the window of times they were allotted. Participants in the control group ate during a mean time of 12.3 hours, while those in the time-restricted group ate during a mean time of 7.6 hours — a difference of 4.8 hours (P < .001).

Both groups were similarly satisfied with their eating window, and 41% in the eTRE group reported that they wanted to continue the intervention. Among those who tried eTRE, 28% said they intended to continue to eat in the 7 a.m. to 3 p.m. window after completing the intervention, and the rest wanted a different time-restricted eating window.

Participants in the control group (4.0 kg [4.2%]; 95% CI, 5.1 to 2.9 kg) and eTRE group (6.3 kg [5.7%]; 95% CI, 7.4 to 5.2 kg) “achieved clinically meaningful weight loss,” but the eTRE group saw an additional loss of 2.3 kg (95% CI, 3.7 to 0.9 kg; P = .002), about a 50% improvement in weight loss. Additionally, those in the eTRE group had lowered their diastolic BP by an additional 4 mm Hg (95% CI, 8 to 0 mm Hg; P = .04).

The researchers also found that eTRE was more effective when it came to improving mood disturbances. These, however, were the only major differences. There were no statistically significant differences in fat loss, the ratio of fat loss to weight loss, systolic BP, insulin levels, heart rate or other measurements.

The trial, the researchers wrote, “lays important groundwork” for future intermittent fasting research in that future studies could assess who can adhere to time-restricted eating and if the duration or timing of the eating window would affect results.

“The eTRE intervention should be further tested as a low-cost, easy-to-implement approach to improve health and treat disease,” they concluded.