Intermittent fasting may be just as effective as traditional calorie-restricted diets for helping people lose weight, according to a comprehensive new review published in The BMJ. The study suggests that certain fasting methods, such as alternate-day fasting, might offer slightly greater benefits. However, researchers caution that longer-term studies are needed to confirm these effects.
The findings come amid rising global concern about obesity.
As of 2022, the World Health Organisation estimated that around 2.5 billion adults worldwide were overweight, and nearly 900 million were classified as obese.
Obesity significantly increases the risk of chronic illnesses like type 2 diabetes, cardiovascular disease, and high blood pressure. Intermittent fasting, an eating pattern that involves cycles of fasting and eating, has grown in popularity as an alternative to traditional calorie-counting diets. However, questions have remained about whether it is equally effective or more beneficial in the long run.
To address this, researchers reviewed data from 99 randomised clinical trials involving more than 6,500 adults, most of whom had pre-existing health conditions and an average BMI of 31.
The studies lasted anywhere from three to 52 weeks, and covered a variety of intermittent fasting styles, including: Time-restricted eating (e.g., 16:8 method) Alternate day fasting (24-hour fast every other day) Whole day fasting (e.g., the 5:2 diet) All forms of intermittent fasting and continuous calorie restriction resulted in small weight reductions compared to diets with no calorie control.
Among the fasting types, alternate-day fasting showed the most notable, though still modest, advantage, producing slightly more weight loss than calorie restriction and other intermittent fasting strategies.