Intermittent fasting is unlikely to produce greater weight loss in overweight or obese adults than standard dietary advice, or even no intervention at all, according to a new Cochrane review.
Obesity remains a major public health challenge and is one of the leading causes of death in high-income countries. The World Health Organization reports that global adult obesity has more than tripled since 1975. In 2022, an estimated 2.5 billion adults were overweight, including 890 million living with obesity.
In recent years, intermittent fasting has gained widespread popularity, propelled by social media, lifestyle influencers, and claims of rapid weight reduction and metabolic improvements.
The review examined 22 randomised controlled trials involving 1,995 adults from North America, Europe, China, Australia, and South America. The studies evaluated several forms of intermittent fasting, including alternate-day fasting, periodic fasting, and time-restricted eating. Most trials followed participants for up to 12 months.
When compared with traditional dietary advice or no intervention, intermittent fasting did not demonstrate a clinically meaningful advantage in terms of weight loss.
Adverse effects were reported inconsistently across studies, limiting the ability to draw firm conclusions about safety. The evidence base remains relatively small, with many trials involving limited sample sizes and variable reporting standards.
Study authors urge caution regarding the strong promotion of fasting online. While intermittent fasting may suit some individuals, current evidence does not support the level of enthusiasm seen on social media platforms.
Long-term data are also lacking. Given that obesity is a chronic condition, short-term studies provide limited guidance for sustained management decisions. Few trials have assessed outcomes beyond one year.
Most participants in the included studies were white and from high-income countries. As obesity rates continue to rise in low- and middle-income settings, further research is needed in more diverse populations.
The authors emphasise that findings cannot be generalised to all groups, as outcomes may differ according to sex, age, ethnicity, underlying health conditions, or disordered eating patterns.
Overall, the authors conclude that current evidence does not support a universal recommendation. Instead, clinicians should adopt an individualised, case-by-case approach when advising patients with overweight or obesity on weight management strategies.
Source: Cochrane
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