A new Cochrane review of 22 clinical trials shows that intermittent fasting does not lead to greater weight loss than standard diet advice for overweight or obese adults. The analysis, involving nearly 2,000 participants, challenges the popularity of fasting methods amid rising global obesity rates. Researchers emphasize the need for more long-term studies and personalized approaches.
Obesity has become a pressing public health issue, with the World Health Organization noting that adult obesity rates have tripled since 1975. In 2022, approximately 2.5 billion adults were overweight, including 890 million living with obesity.
Intermittent fasting, popularized through social media and wellness trends, involves strategies like alternate-day fasting, periodic fasting, and time-restricted feeding. However, a Cochrane review published in 2026 examined 22 randomized clinical trials with 1,995 adults from regions including North America, Europe, China, Australia, and South America. Most trials lasted up to one year.
The review found no clinically meaningful difference in weight loss between intermittent fasting and conventional diet advice or no intervention at all. Side effects were not consistently reported, limiting assessments of risks. The studies primarily involved white participants from high-income countries, highlighting gaps in research for diverse populations.
"Intermittent fasting just doesn't seem to work for overweight or obese adults trying to lose weight," stated Luis Garegnani, lead author from the Universidad Hospital Italiano de Buenos Aires Cochrane Associate Centre. He added, "Intermittent fasting may be a reasonable option for some people, but the current evidence doesn't justify the enthusiasm we see on social media."
The lack of long-term data poses challenges, as obesity is a chronic condition. "Obesity is a chronic condition. Short-term trials make it difficult to guide long-term decision-making for patients and clinicians," Garegnani noted.
Senior author Eva Madrid from the Cochrane Evidence Synthesis Unit Iberoamerica remarked, "With the current evidence available, it's hard to make a general recommendation. Doctors will need to take a case-by-case approach when advising an overweight adult on losing weight."
The authors suggest results may vary by factors such as sex, age, ethnicity, medical conditions, or eating behaviors, calling for further research in low- and middle-income countries.
