An international study suggests that intermittent fasting may not provide significant benefits for overweight or obese individuals, prompting scrutiny from an Australian researcher regarding the review’s limitations.
According to a report by the Cochrane Review, the outcomes associated with intermittent fasting are so minimal compared to traditional weight loss strategies that obese adults might achieve better results by following standard dietary guidelines or opting for no regimen at all.
Researchers from around the globe examined data from 22 randomized clinical trials involving nearly 2,000 adults, including participants from Australia. These trials focused on various intermittent fasting techniques, such as alternate-day fasting, periodic fasting, and time-restricted feeding.
The findings revealed that intermittent fasting did not show a clinically meaningful impact on weight loss.
Professor Leonie Heilbronn, the Group Leader of Obesity and Metabolism at Adelaide University, indicated that the results align with numerous other meta-analyses on the subject. Specifically, intermittent fasting led to weight loss comparable to other moderate calorie restriction methods—around 7% after six to twelve months. In contrast, more effective weight-loss strategies, such as very low-calorie diets (10-15%), pharmacotherapy (15-20%), or surgical interventions (>20%), produced significantly better outcomes.
Nevertheless, she argues that a major shortcoming of the review is the lack of differentiation between various types of intermittent fasting and the neglect of broader health advantages beyond weight loss.
“This review erroneously combines various forms of intermittent fasting,” Professor Heilbronn notes.
“Different types of intermittent fasting are not equivalent for weight loss and should not be grouped together,” she adds.
“Some evidence suggests that time-restricted eating may enhance health outcomes despite modest weight loss, as it better aligns with circadian rhythms.”
She also voices concerns about the limited number of studies reviewed to reach their conclusions.
“It’s important to note that the type of control group can significantly affect the results. In some trials, control groups were not completely inactive; they received some guidance for weight loss, which diminishes the apparent effectiveness of intermittent fasting,” she states.
“The diverse results stem from the fact that various diets are unnecessarily combined, leading to inconsistencies. Some studies included participants with diabetes who often struggle to lose weight, even with medications like semaglutide.”
Professor Heilbronn believes that general practitioners can confidently suggest intermittent fasting as a validated alternative to continuous calorie restriction for periods of six to twelve months, based on existing scientific evidence.
“Numerous individuals face challenges in maintaining weight loss beyond twelve months, regardless of the method employed,” she explains.
“This occurs due to biological mechanisms that promote weight regain post-weight loss.”
“For instance, levels of satiety hormones drop, leading to decreased energy expenditure, while hunger hormones such as ghrelin increase.”
“As a result, people often find themselves regaining weight after a year, whether they followed a calorie-restricted diet or intermittent fasting.”
“Incorporating exercise and weight loss medications can aid in sustaining weight loss by counterbalancing these biological signals.”
Nance Haxton has spent nearly two decades as a journalist at ABC. She has also served as an Advocate at the Disability Royal Commission, helping individuals with disabilities share their stories, and worked as a senior reporter for the National Indigenous Radio Service.
Throughout her career, she has earned numerous Australian and international awards, including two Walkley Awards and three New York Festivals Radio Awards trophies.
Now freelancing as The Wandering Journo, Nance is independently producing podcasts, including her personal audio project titled “Streets of Your Town.”
Subscribe to the free InSight+ weekly newsletter here. The newsletter is accessible to all readers, not only registered medical practitioners.
