Are you trying to lose weight? The 2017 American Heart Association scientific statement on Meal Timing and Frequency may have some answers for you. According to the statement, reducing total calorie intake may be a more effective approach for weight loss than intermittent fasting. So, instead of focusing on the timing and frequency of your meals, consider focusing on overall calorie intake to achieve your weight loss goals.
Both reducing total calories and intermittent fasting can be effective for weight loss, but the best approach for an individual will depend on their specific needs and preferences. Some people find it easier to stick to a consistent calorie restriction, while others prefer the flexibility of intermittent fasting. Consulting with a healthcare professional or a registered dietitian can help determine which approach is best for you.
According to Wendy L. Bennett, M.D., M.P.H., an associate professor of medicine at Johns Hopkins University School of Medicine, while intermittent fasting is a popular weight loss method, there is not yet enough evidence from well-designed studies to confirm its effectiveness in controlling weight.
This research looked into the correlation between the duration of the first and last meals of the day with weight change in nearly 550 adults (18 years old or older) from three health systems in Maryland and Pennsylvania with electronic health records. The participants were enrolled in the study during the period of Feb.-July 2019 and had at least one weight and height measurement recorded in the two years prior to the study.
The majority of the study participants (80%) were white adults, 12% identified as Black, and 3% as Asian. They had a high level of education, the average age was 51 and the average body mass index (BMI) was 30.8, which is considered obese. The study had an average follow-up time of 6.3 years for weight recorded in the electronic health record.
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 developed a mobile application called Daily24 which enabled participants to record their sleep, eating, and wake-up time for each 24-hour period in real-time. The team encouraged participants to use the app frequently during the first month and again during specific “power weeks” which were one week per month throughout the 6-month intervention phase of the study by sending emails, text messages, and in-app notifications.
Based on the timing of sleeping and eating each day recorded in the mobile app, researchers were able to measure:
- the time from the first meal to the last meal each day;
- the time lapse from waking to first meal; and
- the interval from the last meal to sleep.
They calculated an average for all data from completed days for each participant.
The data analysis found:
- 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.
- The 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) were associated with decreasing weight.
- The average time from first to last meal was 11.5 hours; the average time from waking up to first meal measured 1.6 hours; the average time from last meal to sleep was 4 hours; and the average sleep duration was calculated at 7.5 hours.
- The study did not detect an association between meal timing and weight change in a population with a wide range of body weights.
According to Bennett’s report, previous research suggested that intermittent fasting may have benefits for regulating the body’s rhythms and metabolism. However, the study in question, which included a large and diverse group of participants, did not find evidence of this link. Conducting large, well-designed clinical trials on the long-term effects of intermittent fasting on weight change is challenging, but short-term studies may still provide valuable insights for future recommendations.
As stated by Di Zhao, Ph.D., lead study author and associate scientist in the division of cardiovascular and clinical epidemiology at Johns Hopkins Bloomberg School of Public Health, the study results showed that meal frequency and total calorie intake were stronger factors in weight change than meal timing, but it couldn’t establish direct causality between those factors and weight change.
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.
The 2017 American Heart Association scientific statement on Meal Timing and Frequency stated that there was no clear preference for frequent small meals or intermittent fasting. It also noted that irregular patterns of total calorie intake may not be favorable for maintaining body weight and optimal cardiovascular health and that changing meal frequency may not be effective in reducing body weight or improving cardiometabolic risk factors.
This study was funded by an American Heart Association Strategically Funded Research Network Grant to Johns Hopkins University School of Medicine.
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