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Does intermittent fasting burn more fat and help you live longer?

What you hear: “Squeezing your meals into a short daily window (like 16:8) burns more fat than ordinary dieting and helps you live longer.”

What the studies found

A 2026 Cochrane review of 22 trials (1,995 adults) found fasting plans gave about the same weight loss as regular diet advice (a difference of 0.33 percentage points of body weight, not significant). In a 12-month trial, eating only between 8am and 4pm plus calorie limits lost 8.0 kg versus 6.3 kg for calorie limits alone, a 1.8 kg gap that was not significant. A 2025 BMJ analysis of 99 trials found only alternate-day fasting beat steady calorie cutting, by about 1.3 kg, in mostly short trials. Longer life has been shown in mice; in people, observational data instead link eating one meal a day to a 30% higher death rate (a link, not proof).

Take care: In a small trial of people with type 2 diabetes on glucose-lowering medicines, fasting days roughly doubled low-blood-sugar episodes, so anyone taking insulin or diabetes medicines should plan fasting with their doctor.

What you could do

If a shorter eating window helps you eat less, it is a fair option, but pick the plan you can stick with rather than expecting extra fat loss.

See it in the habit library, with what it means for your own longevity score.

Not medical advice. General information from published studies, not a diagnosis or a treatment plan. Talk with your doctor before starting a supplement or changing a medicine, especially if you are pregnant, take other medicines or have a health condition.

How we judged it

Partly true: Some truth, but oversold as usually said. We judge the claim as it is usually said online, not the habit itself. Trials assign people at random, so they can show cause; observed studies follow people and show a link, not proof. Last checked: October 2026.

The studies, in their own words

1. Garegnani et al. Cochrane Database Syst Rev 2026

   Compared to regular dietary advice, intermittent fasting may result in little to no difference in percentage from baseline weight loss (MD -0.33, 95% CI -0.92 to 0.26; 21 studies, 1430 participants; low-certainty evidence due to risk of bias).

2. Liu et al. N Engl J Med 2022

   Changes in weight were not significantly different in the two groups at the 12-month assessment (net difference, -1.8 kg; 95% CI, -4.0 to 0.4; P = 0.11).

3. Semnani-Azad et al. BMJ 2025

   Compared with continuous energy restriction, alternate day fasting was the only form of intermittent fasting diet strategy to show benefit in body weight reduction (mean difference -1.29 kg (95% CI -1.99 to -0.59), moderate certainty of evidence).

4. Sun et al. J Acad Nutr Diet 2023

   Compared with participants eating three meals per day, the multivariable-adjusted HRs for participants eating one meal per day were 1.30 (95% CI 1.03 to 1.64) for all-cause mortality

5. National Institute on Aging news, mouse fasting study

   their findings are encouraging for future studies on how these types of time-restricted eating patterns might help humans

6. Corley et al. Diabet Med 2018

   Fasting increased the rate of hypoglycaemia despite medication reduction (RR 2.05, 95% CI 1.17 to 3.52).

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