Intermittent fasting may make little difference to weight loss, review finds

Source: Hacker News

Overview

A review of 22 studies involving nearly 2,000 adults examined whether short‑term intermittent fasting (up to 12 months) leads to greater weight loss than standard dietary advice or no advice at all.

Types of intermittent fasting

• Eating only during a set period each day
• Fasting on certain days of the week
• Alternating between days of normal eating and days of very low intake

Main findings

• Compared with traditional dieting advice (e.g., reducing calories and eating more healthily), intermittent fasting produced little to no difference in weight loss or quality of life.
• Compared with no advice or waiting for advice, intermittent fasting also showed little to no difference in weight loss; the effect on quality of life was unclear.
• Researchers expressed moderate confidence in these findings but were less confident when comparing intermittent fasting directly with standard dieting, due to methodological limitations in many of the included studies (small sample sizes, less robust designs).

Expert commentary

• Luis Garegnani, lead review author (Universidad Hospital Italiano de Buenos Aires):

  “Intermittent fasting may be a reasonable option for some people, but the current evidence doesn’t justify the enthusiasm we see on social media.”

• Eva Madrid, senior review author:

  “Doctors will need to take a case‑by‑case approach when advising an overweight adult on losing weight.”

• Dr. Baptiste Leurent, associate professor in medical statistics (University College London):

  “Taken together, the individual studies provide a clear indication that intermittent fasting offers little benefit.”

• Prof. Keith Frayn, emeritus professor of human metabolism (University of Oxford):

  “Intermittent fasting has been widely promoted as a means of achieving weight loss—often on the basis of claims it has ‘special effects on metabolism.’ This study shows that such claims can have little relevance. There are no quick fixes for overweight or obese individuals beyond reducing calorie intake.”

Limitations of the evidence

• Many studies lacked robust methodology and involved small participant numbers, making it difficult to determine true effects.
• The review highlighted the need for more detailed data on how different fasting protocols affect men and women separately, as well as variations by BMI, geography, and underlying health conditions (e.g., type 2 diabetes).

Need for further research

The review, published in the Cochrane Database of Systematic Reviews, calls for additional studies to assess:

• Impacts of intermittent fasting on health outcomes beyond weight (e.g., type 2 diabetes, cardiovascular risk).
• Participant satisfaction and quality‑of‑life measures.
• Differences in effectiveness across genders, BMI categories, and cultural contexts.

The included studies were conducted in Europe, North America, China, Australia, and South America.

Context: Other weight‑loss approaches

• Approximately 1.6 million adults in the UK are reported to be using injectable weight‑loss medications such as Wegovy and Mounjaro, primarily via private prescriptions.
• A recent study found that individuals who discontinue these injections may regain weight up to four times faster than those who stop conventional dieting and exercise.

Reference

• Review published in the Cochrane Database of Systematic Reviews – link