There has been a debate going on for a while about what is better for weight loss: intermittent fasting (eating only during designated time periods, without calorie counting) or actually cutting back calories. One recent study examined this issue and found that...drum roll.... the frequency of meals (and calories) a person eats every day is more important for weight loss than intermittent fasting.
Main finding: Large or moderately sized meals (no matter when eaten) were associated with weight gain over the 6 year period of the study, while eating fewer, small meals were associated with weight loss. In other words, the number of meals eaten each day and meal sizes (calories), and not their timing, was most important in determining weight gain or loss.
The results did not support intermittent fasting (time-restricted eating) as a weight loss strategy. Instead, focus on calorie intake. Bummer... You didn't think it would be easy, did you?
Excerpts from Science Daily: Reducing total calories may be more effective for weight loss than intermittent fasting
The frequency and size of meals was a stronger determinant of weight loss or gain than the time between first and last meal, according to new research published today in the Journal of the American Heart Association, an open access, peer-reviewed journal of the American Heart Association.
According to the senior study author Wendy L. Bennett, M.D., M.P.H., an associate professor of medicine at Johns Hopkins University School of Medicine in Baltimore, although 'time-restricted eating patterns' -- known as intermittent fasting -- are popular, rigorously designed studies have not yet determined whether limiting the total eating window during the day helps to control weight.
This study evaluated the association between time from the first meal to last meal with weight change. Nearly 550 adults (18 years old or older) from three health systems in Maryland and Pennsylvania with electronic health records were enrolled in the study. Participants had at least one weight and height measurement registered in the two years prior to the study's enrollment period (Feb.-July 2019).
Overall, most participants (80%) reported they were white adults; 12% self-reported as Black adults; and about 3% self-identified as Asian adults. Most participants reported having a college education or higher; the average age was 51 years; and the average body mass index was 30.8, which is considered obese. The average follow-up time for weight recorded in the electronic health record was 6.3 years.
The research team created a mobile application, Daily24, for participants to catalog sleeping, eating and wake up time for each 24-hour window in real time. Emails, text messages and in-app notifications encouraged participants to use the app as much as possible during the first month and again during "power weeks" -- one week per month for the six-month intervention portion of the study.
The data analysis found:
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- Meal timing was not associated with weight change during the six-year follow-up period. This includes the interval from first to last meal, from waking up to eating a first meal, from eating the last meal to going to sleep and total sleep duration.
- Total daily number of large meals (estimated at more than 1,000 calories) and medium meals (estimated at 500-1,000 calories) were each associated with increased weight over the six-year follow up, while fewer small meals (estimated at less than 500 calories) was associated with decreasing weight.
- The average time from first to last meal was 11.5 hours; average time from wake up to first meal measured 1.6 hours; average time from last meal to sleep was 4 hours; and average sleep duration was calculated at 7.5 hours.
- The study did not detect an association meal timing and weight change in a population with a wide range of body weight.
As reported by Bennett, even though prior studies have suggested intermittent fasting may improve the body's rhythms and regulate metabolism, this study in a large group with a wide range of body weights did not detect this link. Large-scale, rigorous clinical trials of intermittent fasting on long-term weight change are extremely difficult to conduct; however, even short-term intervention studies may be valuable to help guide future recommendations.
Although the study found that meal frequency and total calorie intake were stronger risk factors for weight change than meal timing, the findings could not prove direct cause and effect, according to lead study author Di Zhao, Ph.D., an associate scientist in the division of cardiovascular and clinical epidemiology at Johns Hopkins Bloomberg School of Public Health.
According to the American Heart Association's 2022 statistics, 40% of adults in the U.S. are obese; and the Association's current diet and lifestyle recommendations to reduce cardiovascular disease risk include limiting overall calorie intake, eating healthy foods and increasing physical activity.