Statistics from the American Heart Association for 2022 show that 40% of adults in the U.S. are obese. To lower the risk of cardiovascular disease, the Association recommends limiting overall calorie intake, eating healthy foods, and getting more exercise.

A new study released today in the Journal of the American Heart Heart Association found that the frequency and size of meals were more important than the time between the first and last meal in predicting weight loss or gain.

Although “time-restricted eating patterns,” also known as intermittent fasting, are well-liked, senior study author Wendy L. Bennett, claims that it is unclear whether or not they are effective at regulating body weight.

This study looked at the link between the time between the first and last meals and weight change. The research included over 550 participants (18 years of age or older) from three health systems with electronic health records in Maryland and Pennsylvania. All research participants had at least one documented height and weight assessment from the two years previous to study participation (Feb.-July 2019).

The majority of participants identified as white (80%), followed by 12% who said they were Black and 3% who said they were Asian. The majority of participants claimed to have a bachelor’s degree or above; the average participant was 51 years old; and the average body mass index was 30.8, which is regarded as being obese. The average duration of weight monitoring in the EHR was 6.3 years.

Adults who had a higher body mass index when they joined the study were more likely to be Black, older, have Type 2 diabetes or high blood pressure, have a lower education level, exercise less, eat fewer fruits and vegetables, take longer to go to sleep after their last meal and less time between their first and last meals than adults who had a lower body mass index.

Daily24 is a smartphone app developed by the study team to help participants keep track of when they go to bed, get up, and eat throughout the course of a 24-hour period. Throughout the six-month intervention phase of the trial, participants received emails, texts, and in-app alerts urging them to use the app as much as possible during the first month and again during “power weeks,” one week every month.

Researchers used data from a mobile app to track the timing of sleeping and eating for each participant. They then calculated the average for each of the following: the time between the first and last meals of the day, the time from waking to first meal, and the time from last meal to sleep.

The data evaluation revealed:

• During the six-year follow-up, there was no link between when people ate and how much weight they gained or lost. This includes the time between the first and last meal, the time between getting up and eating the first meal, the time between eating the last meal and going to sleep, and the total amount of time spent sleeping.
• Over a six-year period, eating more large meals (estimated to have more than 1,000 calories) and medium meals (estimated to have between 500 and 1,000 calories) was linked to gaining weight, while eating fewer small meals (estimated to have less than 500 calories) was linked to losing weight.
• The average amount of time between the first and last meals was 11.5 hours. The average amount of time between waking up and the first meal was 1.6 hours. The average amount of time between the last meal and going to sleep was 4 hours. The average amount of time spent sleeping was 7.5 hours.
• In a group of people with different body weights, the study did not find a link between when meals were eaten and how much weight they gained or lost.

According to Bennett, previous studies have shown that intermittent fasting may improve the body’s rhythms and help keep the metabolism in check. However, this study of a large group of people with a wide range of body weights did not find a link between the two. It is very hard to do large-scale, rigorous clinical trials on the long-term effects of intermittent fasting on weight change. However, even short-term intervention studies may be useful to help guide future recommendations.

According to Di Zhao, Ph.D., the study’s lead author, meal frequency and total calorie intake were found to be more significant risk factors for weight change than meal timing. Nevertheless, the study’s findings could not establish a causal link between these factors and weight change.

Researchers say that the study has some flaws because they didn’t look at how timing and frequency of eating interact with each other. Furthermore, since the research was observational in design, the scientists were unable to draw any conclusions on cause and effect. Since most of the study’s participants were well-educated white women from the mid-Atlantic area of the U.S., the authors said that future studies should try to include a more diverse group of people.

Researchers also were not able to assess the intentionality of weight reduction among research participants previous to their enrolment and could not rule out the extra variable of any preexisting health issues.

Source: 10.1161/JAHA.122.026484

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