New research casts doubt on certain claimed benefits of intermittent fasting, finding no link between a person’s timing of meals and their chances of long-term weight loss. The frequency and size of people’s meals, however, was linked to modest changes in weight.
Scientists from the Johns Hopkins Bloomberg School of Public Health recruited adult patients from one of three major health care systems to use an app (“Daily 24”) where they would report their sleeping and eating habits for up to six months. These reports were then used as a barometer for people’s routine eating and sleeping behavior. The researchers also kept track of the volunteers’ health outcomes, including weight, before and after the study began through their electronic medical records. About 550 people used the app during the study period, and the researchers were able to track these people’s weight over an average length of six years.
The team found no significant association between the timing of meals and annual changes in weight in their study sample. People who reported skipping breakfast or taking long breaks between meals, for instance, didn’t noticeably lose or gain any more weight on average than those who didn’t do that. The findings were published Wednesday in the Journal of the American Heart Association.
This type of study is known as observational research, which can only be used to find correlations between two variables, not necessarily a cause-and-effect relationship. And this study in particular wasn’t measuring what might happen to people who newly decide to start intermittent fasting, but rather the possible effects of someone’s regular eating habits on their weight over time. That said, several small trials, including one published last April, have tracked people as they started dieting and have found that intermittent fasting may not provide any added weight loss over a typical eating schedule.
“Based on other studies that have come out, including ours, we are starting to think that timing of meals through the day most likely doesn’t immediately result in weight loss,” lead author Wendy Bennett, an associate professor of medicine in the division of general internal medicine at Johns Hopkins, told CNN.
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Bennett and other researchers studying the topic have cautioned that their results don’t necessarily rule out that intermittent fasting can have some unique positives. It’s possible that some populations, such as those with type 2 diabetes, could experience greater weight loss than they would otherwise while fasting. And for some people, intermittent fasting might simply be easier or preferable as a way to keep track of their eating.
Still, for those who are trying to diet, these findings suggest that there are other patterns they should be more mindful about than timing. The study found that people who ate more frequent medium or large meals during the day gained modest amounts of weight over time (up to two pounds a year linked to every extra meal a day on average). Conversely, eating many small meals throughout the day was linked to a small amount of annual weight loss.