Intermittent fasting has limited effect on weight loss, study finds

Reducing calories proved to be more effective than intermittent fasting for weight loss.
Ayesha Gulzar
Intermittent fasting stock image.
Intermittent fasting stock image.

Sasithorn Phuapankasemsuk/iStock 

Intermittent fasting has been a popular weight loss method in recent years. However, a new study suggests that the timing of meals may not significantly impact long-term weight loss. Instead, calorie restriction appeared to be a better alternative than intermittent fasting for weight loss.

Intermittent fasting is an eating plan that switches between fasting and eating on a regular schedule. The new study, conducted by the Johns Hopkins Bloomberg School of Public Health, investigated the link between the timing of meals and long-term weight loss.

Researchers recruited about 550 adult patients from three major healthcare systems for the study. Participants used an app called "Daily 24" to 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 data collected through the app was used as a barometer for people's routine eating and sleeping behavior. Additionally, the researchers kept track of the participants' health outcomes, including weight, through electronic medical records before and after the study began. Researchers tracked the participant's weight over six years.

The frequency and smaller meals are the keys to weight loss

The results suggest that the timing of meals is not linked to long-term weight loss. Instead, the frequency and smaller meals were associated with weight loss.

"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," said Dr. Wendy Bennett, an associate professor of medicine at Johns Hopkins School of Medicine

The study also showed that the average daily number of large (estimated at more than 1,000 calories) and medium meals (estimated at 500-1,000 calories) led to weight increases.

In contrast, small meals (estimated at less than 500 calories) were associated with decreasing weight, suggesting that overall caloric intake remains a key contributor to weight gain.

Limitations of the study

While the study provides valuable insights, it should not be taken as the definitive answer on the topic of intermittent fasting and weight loss. The authors noted a need for more research on a more diverse population.

The researchers also said they couldn't tell if people were trying to lose weight before they joined the study and if existing health conditions made a difference. Those factors could be important for getting a better look at the effects of meal timing.

The study was observational, meaning that they looked at existing patterns for the study instead of making changes to a randomized group.

There is no one-size-fits-all approach to weight loss

For some people, intermittent fasting or restricting eating intervals can be a helpful way to take note of personal tendencies and eating habits that could lead to weight loss.

However, it is important to remember that there is no one-size-fits-all approach to nutrition and weight loss. Different people have different dietary needs and preferences, and what works for one person may not work for another.

“If you make some effort to consume a healthy diet, you make some effort to be physically active, you’re less likely to have diabetes, chronic kidney you're, obstructive pulmonary disease, and hypertension,” said Alice Lichtenstein, professor of nutrition science and policy at Tufts University to CNN.

The study was published in the Journal of the American Heart Association.


Background: We aim to evaluate the association between meal intervals and weight trajectory among adults from a clinical cohort.

Methods and Results: This is a multisite prospective cohort study of adults recruited from 3 health systems. Over the 6‐month study period, 547 participants downloaded and used a mobile application to record the timing of meals and sleep for at least 1 day. We obtained information on weight and comorbidities at each outpatient visit from electronic health records for up to 10  years before until 10 months after baseline. We used mixed linear regression to model weight trajectories. Mean age was 51.1 (SD 15.0) years, and body mass index was 30.8 (SD 7.8) kg/m2; 77.9% were women, and 77.5% reported White race. Mean interval from first to last meal was 11.5 (2.3) hours and was not associated with weight change. The number of meals per day was positively associated with weight change. The average difference in annual weight change (95% CI) associated with an increase of 1 daily meal was 0.28 kg (0.02–0.53).

Conclusions: Number of daily meals was positively associated with weight change over 6 years. Our findings did not support the use of time‐restricted eating as a strategy for long‐term weight loss in a general medical population.

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