Number and Size of Daily Meals, Not Intermittent Fasting, Associated with Long-term Weight Loss in New Study

Long-term weight loss is associated with the average daily number of medium and large meals but not with a specific time-restricted eating strategy, according to new research published in the Journal of the American Heart Association.

In an electronic health record-based cohort study of 547 participants from 3 US health systems, the number of daily meals was positively associated with weight change over a median of 6.3 years; however, the time interval between first and last meal was not associated with weight change.

Previous studies suggest that the timing of food consumption (eg, through intermittent fasting or time-restricted feeding) could regulate metabolic function and reduce body weight, however, no population-based, longitudinal studies have been designed to specifically evaluate the association between meal intervals and changes in weight, according to researchers.

“In addition to windows between meals, the role of the frequency and size of meals on weight has been also controversial,” wrote senior author Wendy L. Bennett, MD, MPH, associate professor of medicine, Johns Hopkins University School of Medicine, and colleagues. “Cross‐sectional studies have shown that a greater meal frequency was either not associated or associated with a reduced prevalence of abdominal and general obesity, while 2 large‐scale prospective cohort studies showed that greater meal frequency was associated with increased weight gain and body mass index (BMI).”

Bennett and colleagues recruited 547 adults aged ≥18 years with electronic health records from 1 of 3 health systems, who had at least 1 weight and height measurement within 2 years before the enrollment window (February 2019-July 2019). Overall, the mean age of participants was 51.1 years, mean BMI was 30.8 kg/m², 77.9% were women, and 77.5% were White.

Over a 6-month study period, participants downloaded and used a mobile application the research team created called Daily24. On the app, participants recorded their timing of meals and sleep for at least 1 day. Investigators assessed data on weight and comorbidities at all outpatient visits for up to 10 years before until 10 months after baseline and modeled weight trajectories.

The mean interval from first to last meal was 11.5 hours and was not associated with weight change, according to study results. In adjusted models, each 1-hour increase in time from first to last meal at baseline was associated with a 0.005 kg (95% CI, -.08 to .09) average annual weight change. The annual weight changes during follow-up associated with time from wake up to sleep, time from last meal to sleep, and sleep duration were 0.02 kg (95% CI, -0.08 to 0.12), 0.07 kg (95% CI, -.03 to 0.17), and 0.11 kg (95% CI, -.06 to 0.28), respectively.

Investigators observed that the total daily number of large meals (>1000 calories) and medium meals (500-1000 calories) were each associated with increased weight over the 6-year follow up, while fewer small meals (<500 calories) were associated with decreasing weight. The average annual weight changes associated with a daily increase of 1 large, medium, or small meal were 0.69 kg (95% CI, 0.19 to 1.18), 0.97 kg (95% CI, 0.64 to 1.29), and −0.30 kg (95% CI, −0.53 to −0.07), respectively.

The distribution of energy intake earlier during the day appeared to be associated with less weight increase after enrollment, noted researchers.

“Our findings did not support the use of time‐restricted eating as a strategy for long‐term weight loss. Further large‐scale studies with long follow‐up time are needed to better characterize the association for time of eating with weight change,” concluded Bennett et al.

Reference: Bennett WL, Zhao D, Guallar E, et al. Association of eating and sleeping intervals with weight change over time: The Daily24 cohort. J Am Heart Assoc. Published online January 18, 2023. doi:10.1161/JAHA.122.026484.