Alternate day fasting—the practice of fasting every other day—may be more effective for weight loss than other popular intermittent fasting methods or continuous calorie restriction. This conclusion comes from a comprehensive review analyzing data from 99 studies involving over 6,500 participants.
Intermittent fasting has surged in popularity in recent years, with additional approaches like time-restricted eating (such as the 16:8 diet, where one fasts for 16 hours and eats during an 8-hour window) and whole-day fasting plans (like the 5:2 diet, involving two fasting days per week) also attracting attention.
The multinational research team from Scotland, the US, Canada, and Germany sought to directly compare these fasting strategies against traditional continuous calorie restriction diets. Participants in the analyzed studies had an average Body Mass Index (BMI) of 31, with nearly 90% presenting pre-existing health conditions.
While both intermittent fasting and calorie-restriction diets led to weight loss, alternate day fasting stood out as the only method producing a statistically significant greater reduction in body weight compared to continuous energy restriction. On average, those following alternate day fasting lost 1.29 kg more than those on traditional diets, according to findings published in The BMJ.
The researchers described the weight difference as modest but meaningful, noting other intermittent fasting approaches like time-restricted eating and whole-day fasting did not significantly outperform continuous calorie restriction. They summarized, “Alternate day fasting demonstrated a benefit in weight reduction compared to continuous energy restriction, whereas time-restricted eating and whole-day fasting did not.”
With obesity affecting nearly 29% of adults in the UK, these insights hold particular relevance. Meanwhile, the NHS is preparing to expand access to new weight loss medications such as tirzepatide (marketed as Mounjaro), potentially offering additional powerful tools in tackling obesity—a health concern prompting comparisons to the transformative impact of statins.