- Intermittent fasting has become a popular health trend, but research in this area is still ongoing.
- A recent review found that intermittent fasting may not offer major benefits when it comes to weight loss.
- Additional research into this area may be helpful to understand the full effects of intermittent fasting and how it may help people with certain conditions.
Intermittent fasting has become the subject of recent research, and it is sometimes suggested as a way to help with weight loss.
A review published in the Cochrane Library put this idea to the test by looking at what studies actually showed about the benefits and harms of intermittent fasting.
Overall, the results suggested that intermittent fasting does not help much with weight loss, compared to receiving traditional weight loss treatment or not receiving treatment at all.
While addressing obesity is still important, intermittent fasting may not provide much help, but more research is likely required in this area.
The authors of this review highlight the problem of obesity and how it is a risk factor for health problems like cancer. Intermittent fasting involves a number of different eating patterns, where there are timeframes of food intake and periods with little or no intake.
There is variation, and people may also pair this with special diets when they are eating. For this review, researchers wanted to specifically examine the relationship between intermittent fasting and weight. In addition to weight loss, other critical outcomes included adverse events and quality of life.
This review specifically focused on randomized controlled trials and cluster-randomized controlled trials, where the fasting intervention was at least four weeks, and the minimum follow-up was at least six months.
In all, the authors included 22 studies using data from 1,995 participants between them. All participants were at least 18 years old and had overweight or obesity.
Researchers looked at studies that compared intermittent fasting to traditional dietary advice, as well as those that compared it to no intervention or being on a waiting list to receive treatment.
Most studies compared intermittent fasting to other strategies, such as reducing calorie intake. The most common intermittent fasting method was time-restricted feeding, which involves only eating within a specific timeframe each day. Thirteen of the studies combined intermittent fasting with other interventions like nutritional guidance.
Compared to regular dietary advice, researchers concluded that intermittent fasting may have little to no impact on weight loss, quality of life, or adverse events.
Researchers were more confident about their findings comparing intermittent fasting to being on a waiting list for treatment or receiving no treatment. However, this analysis only included six studies.
They concluded with moderate certainty that intermittent fasting has little to no effect on weight loss. They concluded with very low certainty that it has little to no impact on the “general physical health domain of quality of life,” and a similar finding for adverse events.
Intermittent fasting also may not have a major impact on total cholesterol or triglycerides. However, it might increase levels of good cholesterol. Sensitivity analyses revealed similar findings to the initial analyses.
In the subgroup analyses, researchers did find some differences for adverse events. For example, compared to regular dietary advice, men may be more likely to experience adverse events from intermittent fasting than women, although there is a need for more research in this area.
They also found some differences when it came to triglycerides and different methods of intermittent fasting when compared to no intervention or being on a waiting list.
This review does have limitations, both from the data and methods used. Researchers faced challenges from high workloads and having to label some information as awaiting classification due to a lack of information.
There is a possibility that this review does not provide complete information, and there is likely a need for more research.
Researchers assessed each study’s risk for bias “for the results of the primary outcomes.” They note that for most outcomes, there was an overall high risk of bias.
Furthermore, there was a lack of data in a number of areas. For example, the authors noted that none of the studies included information about diabetes status, participant satisfaction, or an overall measure of comorbidity, or co-occurring conditions. Additionally, less than half of the studies reported on participant adherence to the intervention.
There are also the limitations of the individual trials included in the review. For instance, most of the studies did not have a follow-up timeframe that lasted longer than a year.
Most were single-center studies, seven trials focused mainly on female participants, and a majority were conducted in high-income countries, accounting mainly for white participants.
In some of the studies included, intermittent fasting was often combined with other interventions, and it is unclear how these impacted trial results. The authors noted that most of the studies also “reported results that were inconclusive.”
Finally, body mass index (BMI) also has limitations as a weight measurement. The authors of the review themselves highlighted that BMI “is not a reliable indicator of obesity at the individual level,” though it is what they used in this review to determine overweight or obesity.
Priya Kalia, MD, a family medicine and obesity medicine board-certified doctor, and assistant professor in family medicine, who was not involved in this research, commented the following regarding the review:
“According to this Cochrane review, from the available randomized evidence, there’s not much of a difference [between] intermittent fasting compared to standard caloric restricted diet. One key point is that major metabolic outcomes — like diabetes prevention, diabetes remission, or long-term cardiometabolic risk — were not well studied or reported in these trials. Also, 5 lb [pounds] of muscle is not the same as 5 lb of fat when it comes to metabolic health. It would be nice to see studies incorporate body compositional analysis to have better measured outcomes.”
This review findings do not necessarily imply that people should avoid intermittent fasting, but they suggest this dietary approach might not provide the benefits that some people hope for.
It is something people should discuss with their doctors if they are interested in exploring how it might benefit them.
Kalia noted to Medical News Today that “intermittent fasting should be viewed as a dietary structure, adjuvant, not a metabolic therapy.“
“If a patient finds it simple, sustainable, and it helps them reduce calories without adverse effects, it can be a reasonable option. But it shouldn’t be marketed as metabolically superior, nor should patients feel they’re missing out on benefits if another approach works better for them,“ she cautioned.
“The strongest predictors of metabolic improvement remain the fundamentals: sustained weight loss, diet quality, physical activity, sleep, and — when appropriate — evidence-based medications like GLP-1 receptor agonists. Meal timing alone isn’t a substitute for those,” Kalia explained.
Mir Ali, MD, a bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, likewise not involved in the research also advised:
“In my experience, time-restricted eating can be effective, particularly when paired with a balanced, nutrient-dense diet. Both the quantity and quality of calories are critical; without improvements in food choices, results are often limited. For patients interested in time-restricted eating, I recommend beginning with a shorter fasting window, such as 12 hours, and gradually extending it to 14–16 hours as tolerated. Maintaining proper nutrition is essential, with an emphasis on adequate protein intake, vegetables, and minimizing refined carbohydrates and added sugars.”
