Intermittent fasting has surged in popularity with huge enthusiasm for the diet on social media – but research suggests simply fasting is unlikely to lead to weight loss.
The diet trend promises to hack biology without counting calories. Instead, it involves fasting for an extended period and then eating breakfast, lunch and dinner in a condensed eight-hour window.
Obesity is a significant public health problem that has become a leading cause of death in high-income countries. In 2022, 2.5 billion adults were overweight; of these, 890 million were living with obesity. In England, more than two-thirds of adults are estimated to be overweight or obese.
Being overweight or obese is a leading cause of cancer, second only to smoking, and is linked to at least 13 types of the disease.
But intermittent fasting is unlikely to lead to greater weight loss in overweight or obese adults than traditional dietary advice or doing nothing, a new Cochrane review has found.
“Intermittent fasting may be a reasonable option for some people, but the current evidence doesn’t justify the enthusiasm we see on social media,” said Luis Garegnani, lead author of the review from the Universidad Hospital Italiano de Buenos Aires Cochrane Associate Centre. “Intermittent fasting just doesn’t seem to work for overweight or obese adults trying to lose weight.”
The review analysed evidence from 22 randomised clinical trials involving 1,995 adults across North America, Europe, China, Australia, and South America.
The trials examined multiple forms of intermittent fasting, including alternate-day fasting, periodic fasting, and time-restricted feeding. Most studies followed participants for up to 12 months.
Researchers found intermittent fasting does not have a clinically meaningful effect on weight loss compared to standard dietary advice or doing nothing.
“Intermittent fasting is not a magic solution for weight loss,” Kim Pearson, a nutritionist specialising in weight loss, told The Independent. She explained that while it can help people reduce their calorie intake, as shown in the review, improving overall diet quality is more likely to help with weight loss.
“More aggressive approaches are often difficult to sustain and do not address the root causes of weight gain, such as poor diet quality, excess ultra-processed foods and blood sugar instability,” she said.
Instead, she urges people to focus on eating protein, fibre and healthy fats while reducing ultra-processed foods, sugar and refined starchy carbohydrates.
“This helps regulate appetite naturally, supports stable blood sugar and allows the body to burn stored body fat more efficiently,” she added.
Rob Hobson, registered nutritionist and author of the low appetite cookbook, also suggests eating minimally processed foods, protein and fibre. He warns that fasting can lead to overeating later.
He told the Independent: “Where fasting can fall down is adherence because restrictive eating windows or very low-intake days can ( in some people) lead to compensatory overeating, low energy, or simply not being sustainable over the long term, and it’s long-term consistency that really drives results when it comes to weight loss.”
Dr Earim Chaudry, chief medical officer at online pharmacy Voy, added that weight loss isn’t a “matter of willpower” and while fasting can help in the short term, it’s not more effective than changing your diet and lifestyle.
“Limiting eating windows does not address the biological drivers of appetite, metabolic adaptation and weight regain, and it is often difficult to sustain,” he told The Independent.
However, Ms Pearson explains there could be some benefits to fasting because not eating overnight for 12-14 hours “aligns with our circadian biology and gives the body time to move out of a constant fed state”, she said. But she stressed there is no need for extreme fasting.
