Reducing Total Calories, Not Intermittent Fasting, More Effective for Weight Loss

Wendy Bennett, MD, MPH

Results of a 6-year study of more than 500 adult patients indicate the frequency and size of meals was a stronger determinant of weight loss than time between meals, suggesting reducing caloric intake may be a more effective approach for weight management than intermittent fasting.

A multisite prospective cohort study of patients within the PaTH Clinical Research Network, results of the study demonstrate no association between meal timing and weight change was observed, but the number of meals per day was associated with weight change, with each additional meal per day associated with a mean annual weight change of more than half a pound.

“Importantly, we found an association between the eating of more frequent and larger meals per day and weight increase, indicating that total overall caloric intake is the major driver of weight gain,” wrote investigators.

Funded by an American Heart Association Strategically Funded Research Network Grant to Johns Hopkins University School of Medicine, the current study was led by Wendy Bennett, MD, MPH, an associate professor of medicine at Johns Hopkins University School of Medicine, with the intent of exploring how the impact of between meal intervals and other factors on weight trajectory among a cohort of adult patients. Named the Daily24 cohort, patients included in the current study were aged 18 years or older, recruited from 3 health care systems within the PaTH Clinical Research Network, and had electronic health record data with at least 1 weight and height measurement within 2 years before the study’s enrollment window, which took place from February 1, 2019-July 31, 2019.

Patients included in the study were instructed to use the Daily24 mobile application, which was designed to record timing of waking up, sleeping, and each eating occasion for each 24-hour window in real-time for each participant. As part of study protocol, all participants completed an online survey at enrollment and were asked to report weight at baseline and in a 4-month follow-up survey. Investigators pointed out EHR data was used to assess all weight and height information from up to 10 years before enrollment and until 10 months after enrollment. For the purpose of analysis, mixed linear regression was used to model weight trajectories.

Overall, 1017 individuals completed baseline surveys. After exclusion of those who did not download the Daily24 mobile app and those who did not use it for at least 1 day, investigators identified a final sample of 547 individuals. This cohort had a mean BMI of 30.8 (SD, 7.8) kg/m2, a mean age of 49.3 (SD, 15.0) years, 20.1% were men, 79.9% were White, and a mean follow-up time of 6.3 (SD, 2.9) years. Among the cohort, the mean times from first to last meal, wake up to first meal, last meal to sleep, and sleep duration of study participants were 11.5 (SD, 2.3), 1.6 (SD, 1.9), 4.0 (SD, 2.1), and 7.5 (SD, 1.2) hours, respectively.

Upon analysis, results indicated the time from first to last meal, wake up to first meal, last meal to sleep, and total sleep duration at enrollment were not associated with weight change during the follow-up period. 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, -0.08 to 0.09) average annual weight change.

Further analysis suggested total daily number of large and medium meals was associated with increased weight during follow-up, while decreasing weight was observed for those with total number of small meals. Specifically, the average annual weight changes associated with a daily increase of a single, 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 window of time between first to last meal was not associated with weight change over an average of about 6 years of follow-up. However, the average daily number of large and medium meals was associated with increased weight over time, suggesting that the meal frequency and meal sizes, rather than the timing of meals, was a stronger determinant of weight gain over time,” wrote investigators.

This study, “Association of Eating and Sleeping Intervals With Weight Change Over Time: The Daily24 Cohort,” was published in the Journal of the American Heart Association.