Research Highlights:
Embargoed until 4 a.m. CT/5 a.m. ET, Wed., Jan. 18, 2023
DALLAS, Jan. 18, 2023 — 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.
Participants with a higher body mass index at enrollment were more likely to be Black adults, older, have Type 2 diabetes or high blood pressure, have a lower education level, exercise less, eat fewer fruits and vegetables, have a longer duration from last mealtime to sleep and a shorter duration from first to last meal, compared to the adults who had a lower body mass index.
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.
Based on the timing of sleeping and eating each day recorded in the mobile app, researchers were able to measure:
They calculated an average for all data from completed days for each participant.
The data analysis found:
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.
Researchers note there are limitations to the study since they did not evaluate the complex interactions of timing and frequency of eating. Additionally, since the study is observational in nature, the authors were unable to conclude cause and effect. Future studies should work toward including a more diverse population, since the majority of the study’s participants were well-educated white women in the mid-Atlantic region of the U.S., the authors noted author.
Researchers also were not able to determine the intentionality of weight loss among study participants prior to their enrollment and could not rule out the additional variable of any preexisting health conditions.
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.
The 2017 American Heart Association scientific statement: Meal Timing and Frequency: Implications for Cardiovascular Disease Prevention did not offer clear preference for frequent small meals or intermittent fasting. It noted that irregular patterns of total caloric intake appear to be less favorable for the maintenance of body weight and optimal cardiovascular health. And, altering meal frequency may not be useful for decreasing body weight or improving traditional cardiometabolic risk factors.
Other co-authors of this study are Eliseo Guallar, M.D., Dr. P.H.; Thomas B. Woolf, Ph.D.; Lindsay Martin, M.A.; Harold Lehmann, M.D., Ph.D.; Janelle Coughlin, Ph.D.; Katherine Holzhauer, B.A.; Attia A. Goheer, Ph.D.; Kathleen M. McTigue, M.D., M.P.H., M.S.; Michelle R. Lent, Ph.D.; Marquis Hawkins, Ph.D.; and Jeanne M. Clark, M.D., M.P.H. Authors’ disclosures are listed in the manuscript.
This study was funded by an American Heart Association Strategically Funded Research Network Grant to Johns Hopkins University School of Medicine.
Studies published in the American Heart Association’s scientific journals are peer-reviewed. The statements and conclusions in each manuscript are solely those of the study authors and do not necessarily reflect the Association’s policy or position. The Association makes no representation or guarantee as to their accuracy or reliability. The Association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific Association programs and events. The Association has strict policies to prevent these relationships from influencing the science content. Revenues from pharmaceutical and biotech companies, device manufacturers and health insurance providers and the Association’s overall financial information are available here .
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Journal of the American Heart Association
Association of Eating and Sleeping Intervals With Weight Change Over Time: The Daily24 Cohort