A recent scientific review has revealed that intermittent fasting is no more effective than traditional dietary advice, or even no diet at all, in reducing weight in obese or overweight adults.
Obesity is a major public health problem and a leading cause of death in high-income countries. Globally, the rate of obesity among adults has more than tripled since 1975, according to the World Health Organization. In 2022, 2.5 billion adults were overweight, including 890 million who were obese.
Intermittent fasting has seen a surge in popularity in recent years, fueled by social media, lifestyle influencers, and claims of rapid weight loss and metabolic benefits.
In a new review, researchers from the Cochrane Database of Systematic Reviews analyzed data from 22 randomized clinical trials involving 1,995 adults from North America, Europe, China, Australia, and South America. These trials explored various forms of intermittent fasting, including alternate-day fasting, cyclical fasting, and time-restricted eating, with most participants being followed for up to 12 months.
The researchers found no real difference in weight loss between people who followed intermittent fasting and those who stuck to the usual dietary advice, or even compared to those who did not follow any specific regimen.
Furthermore, information on the side effects of fasting was incomplete and inconsistent in most studies, making it difficult for researchers to reach definitive conclusions. The number of studies is also limited, and many are small or lack accurate data documentation.
"Intermittent fasting simply doesn't seem to work for overweight or obese adults who are trying to lose weight," said Luis Garignan, lead author of the review from the Cochrane Library's University Hospital Italiano Center in Buenos Aires.
Garignan also cautioned against the online hype surrounding fasting, noting that while intermittent fasting may be a reasonable option for some, current evidence does not justify the widespread enthusiasm seen on social media. He added that obesity is a chronic condition, and short-term experiences make it difficult to guide long-term decisions for both patients and doctors.
The researchers noted that the majority of studies included white populations in high-income countries. Since obesity is a rapidly growing crisis in low- and middle-income countries, more research is urgently needed in these population groups.
The researchers caution that these findings only provide indicators and cannot be generalized to the entire population, as they may vary according to gender, age, ethnic origin, health status, or underlying eating disorders.
