Calorie restriction is more effective for weight loss than intermittent fasting: Study
A study found that large meals are more beneficial than intermittent fasting.
The study was published in the Journal of the American Heart Association. According to senior study author Wendy L. Bennett, MD, MPH, associate professor of medicine at the Johns Hopkins University School of Medicine in Baltimore, despite the popularity of “time-restricted eating patterns” — known as intermittent fasting — , but well-designed studies have yet to determine whether restricting total eating time during the day helps control weight.
This study assessed the association between the time from first to last meal and weight change. Nearly 550 adults (age 18 or older) with electronic health records from three health systems in Maryland and Pennsylvania participated in the study. Participants registered weight and height measurements at least once in the two years preceding the study enrollment period (February-July 2019).
Overall, the majority of participants (80%) indicated they were white adults; 12% identified themselves as black adults; and about 3% identified themselves as Asian adults. Most participants indicated college or higher education; mean age was 51; mean body mass index was 30.8, which is considered obese. The average follow-up time for weights recorded in electronic health records 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, be less educated, exercise less, eat fewer fruits and Adults with a longer last meal were more likely to fall asleep and had a shorter duration from their first meal to their last meal than adults with a lower BMI.
The research team created a mobile app called Daily24 for participants to record in real time when they sleep, eat and wake up for each 24-hour window. Emails, text messages, and in-app notifications encouraged participants to use the app as much as possible during the first month, and to use the app again during “power weeks” — one week per month during the six-month study intervention part.
From daily sleep and meal times recorded in the mobile app, the researchers were able to measure:
– the time from the first to the last meal of the day;
– time from waking up to first meal; and
– Time interval from last meal to bedtime.
They calculated the average of all data for the number of days completed by each participant.
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 first meal, from last meal to falling asleep, and total sleep time.
– At six-year follow-up, the total number of daily large meals (estimated to be more than 1,000 calories) and medium meals (estimated to be 500-1,000 calories) was associated with weight gain, while fewer small meal (estimated to be less than 500 calories) calories ) are associated with weight loss.
– The average time from first meal to last meal was 11.5 hours; the average time from waking up to first meal was 1.6 hours; the average time from last meal to sleep was 4 hours; average sleep time was calculated as 7.5 hours.
– The study found no association between meal timing and weight change in a population with a wide range of weight changes.
As Bennett reports, while previous research has suggested that intermittent fasting may improve the body's rhythms and regulate metabolism, this study of a large group of people with a wide range of weights found no such link. Clinical trials of large-scale, rigorous intermittent fasting on long-term weight change are extremely difficult; however, even studies of short-term interventions may help guide future recommendations.
Although the study found meal frequency and total calorie intake to be stronger risk factors for weight change than meal timing, the findings could not prove direct cause and effect, said the study's lead author, Dr. Di Zhao, an associate scientist at The Johns Hopkins Department of Cardiovascular and Clinical Epidemiology, University of Bloomberg School of Public Health.
The researchers noted that the study was limited in that they did not assess the complex interplay of timing and frequency of eating. Also, because the study was observational in nature, the authors were unable to draw causality. The authors note that future studies should strive to include a more diverse population, since most of the study's participants were white, well-educated women in the mid-Atlantic United States.
The researchers also could not determine the study participants' weight loss intentions before enrollment, nor could they rule out any additional variables of pre-existing health conditions.
According to the American Heart Association's 2022 statistics, 40% of adults in the United States are obese; the association's current diet and lifestyle recommendations to reduce the risk of cardiovascular disease include limiting total calorie intake, eating healthy foods, and increasing physical activity .