Intermittent Fasting Fails to Deliver Superior Weight Loss Results, Major Study Concludes
Intermittent fasting, a diet trend that has exploded in popularity across social media platforms, is unlikely to lead to greater weight loss in overweight or obese adults than following standard healthy eating advice or making no dietary changes at all. This is the key finding from a new Cochrane review, which analysed evidence from 22 randomised clinical trials involving nearly 2,000 participants worldwide.
The Hype Versus the Evidence
The diet, which involves fasting for extended periods—such as condensing breakfast, lunch, and dinner into an eight-hour window—promises to hack biology without calorie counting. However, the review, led by researchers from the Universidad Hospital Italiano de Buenos Aires Cochrane Associate Centre, found no clinically meaningful difference in weight loss outcomes when comparing intermittent fasting to conventional dietary guidance or no intervention.
"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, the review's lead author. "Intermittent fasting just doesn't seem to work for overweight or obese adults trying to lose weight."
Understanding the Global Obesity Crisis
Obesity remains a critical public health challenge, recognised as a leading cause of death in high-income nations. In 2022, global figures indicated 2.5 billion adults were overweight, with 890 million living with obesity. In England alone, more than two-thirds of adults are estimated to be overweight or obese. Being overweight or obese is a primary risk factor for cancer, linked to at least 13 types of the disease, and is second only to smoking as a cause.
The Cochrane review examined various forms of intermittent fasting, including alternate-day fasting, periodic fasting, and time-restricted feeding. Most studies followed participants for up to twelve months, providing a robust long-term perspective.
Expert Insights on Sustainable Weight Management
Nutrition experts emphasise that while intermittent fasting can help reduce calorie intake, it is not a magic solution. "Intermittent fasting is not a magic solution for weight loss," explained Kim Pearson, a nutritionist specialising in weight management. She noted that more aggressive dietary approaches are often difficult to maintain and fail to address underlying causes of weight gain, such as poor diet quality, excessive consumption of ultra-processed foods, and blood sugar instability.
Pearson advocates for a 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, a registered nutritionist and author, echoes this sentiment, warning that fasting can lead to compensatory overeating later. "Where fasting can fall down is adherence because restrictive eating windows or very low-intake days can lead to compensatory overeating, low energy, or simply not being sustainable over the long term," he told The Independent. "It's long-term consistency that really drives results when it comes to weight loss."
The Biological and Psychological Factors
Dr Earim Chaudry, chief medical officer at online pharmacy Voy, highlighted that weight loss is not merely a matter of willpower. While fasting might offer short-term benefits, it is not more effective than comprehensive diet and lifestyle changes. "Limiting eating windows does not address the biological drivers of appetite, metabolic adaptation and weight regain, and it is often difficult to sustain," he explained.
Despite these criticisms, Pearson acknowledged potential benefits to fasting, such as aligning with circadian biology by not eating overnight for 12-14 hours, which gives the body time to move out of a constant fed state. However, she stressed that extreme fasting is unnecessary and that sustainable, balanced eating habits are paramount for long-term health and weight management.
The findings challenge the widespread social media promotion of intermittent fasting as a superior weight loss strategy, urging a more nuanced and evidence-based approach to dietary interventions in the fight against obesity.
