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Pooled review (meta-analysis)

Pooled review of 99 studies: only alternate day fasting beat calorie cutting

Semnani-Azad and colleagues · BMJ (Clinical research ed.) · 2025

Original title: Intermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis of randomised clinical trials.

Under review. A person has not yet checked this summary against the paper. It is written from the PubMed abstract. Until a person checks it, search engines are asked not to list this page.

What the study found

Mixed

All fasting plans and calorie cutting lost weight vs eating freely. Vs calorie cutting, only alternate day fasting did better: mean difference -1.29 kg (95% CI -1.99 to -0.59). Trials of 24 weeks or more showed no gap.

The study at a glance

Type of study
Pooled review (meta-analysis)
Who or what was studied
99 studies, 6,582 people · adults, healthy or with health conditions
What was tested
alternate day fasting, time restricted eating and whole day fasting, vs daily calorie cutting or eating freely; mostly under 24 weeks
What it measured
The question itself: weight loss, compared with ordinary calorie cutting
Trial registration
NCT05309057
Who has a stake
Company stake
Several authors report fees or advisory roles with Novo Nordisk, Eli Lilly and food companies; none stated for fasting products.
Journal
BMJ (Clinical research ed.), 2025
Source
PubMed record 40533200. This page is based on the abstract only.

How much this study counts

  • ✓Pools the results of 99 studies with 6,582 people.
  • •A pooled review is only as strong as the studies it pools.
  • ✓Measured the question itself: weight loss, compared with ordinary calorie cutting.
  • –Company stake: Several authors report fees or advisory roles with Novo Nordisk, Eli Lilly and food companies; none stated for fasting products.
  • •Summarized from the PubMed abstract only. The full paper may hold details the abstract leaves out.

✓ Strength– Limit• Note

These points come from fixed rules about the type of study, its size and length, what it measured, and who has a stake. Every study on Digestery gets the same rules.

Where this study sits

This paper is not on the ladder. It is a pooled review (meta-analysis), and reviews and opinion pieces discuss studies that are already counted on the steps below.

↑ Stronger evidence

  1. Trials in people: weight loss

    9

    5 benefit, 2 mixed, 2 no difference

  2. Trials in people: other measures

    8

    4 benefit, 3 mixed, 1 no difference

  3. Trials in people: lab tests or safety

    1

    1 benefit

  4. Population studies

    0

    None among the papers we read.

  5. Blood levels and genes

    0

    None among the papers we read.

↓ Weaker evidence

  • Points to benefit
  • Mixed
  • No difference
  • No direction
  • Points to harm

How it fits with the other research

The short answer to “Does intermittent fasting help with weight loss?”

Yes, but about like calorie cutting.

Confidence: moderate. Based on 26 on-topic papers.

Read the full answer
  • Quoted in “What we found”: Compared with eating freely, all fasting plans and daily calorie cutting lowered weight in a pooled analysis of 99 trials with 6582 adults.
  • Quoted in “What we found”: Only alternate-day fasting beat calorie cutting in the 99-trial analysis (mean difference -1.29 kg), and trials of 24 weeks or more showed no such gap.
  • Part of the finding “Fasting beats eating as usual”.
  • Part of the finding “Alternate-day fasting may edge ahead, short term”.
  • Summed up in “What reviews found”: Pooled 99 randomized trials with 6582 adults. All fasting plans and calorie cutting lowered weight versus eating freely. Only alternate-day fasting beat calorie cutting (-1.29 kg), and not in trials of 24 weeks or more.
  • Marked as a key paper in the research timeline: Biggest review: 99 trials, fasting about equals calorie cutting.
  • Open item for a person: Pooled reviews Semnani-Azad 2025, Elortegui Pascual 2023, Zhang 2022 and Welton 2020 likely share many trials; their results are not independent.

Other reviews on this question

See all 26 studies on this question

How this page was made

Label

First read of the abstract
Claude Sonnet
Independent second read
Claude Haiku
Differences settled
The two reads agreed on every checked field. Claude Opus 5.5.
Headline
Claude Sonnet, from the checked study record. A script checked its numbers and wording.
Numbers
Checked against the abstract by a script
“How much this study counts”
Fixed rules, the same for every study
Source check by a person
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