Diets

intermittent fasting decreases body weight

In plain terms: Does intermittent fasting help you lose weight?

Strong support Diets 🔬 Includes disconfirming

Part of: 🥗 intermittent fasting

RefutedContestedStrong support

consensus score 0.78

Yes, but the benefit comes mostly from eating fewer calories, not the timing itself.

📅 Last reviewed: 2026-07-15 ⓘ

Evidence ladder

How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."

Top evidence so far: All trials, pooled (Meta-analysis)

MechanismIn-vitroAnimalObservationalRCTMeta-analysis

How the studies fall

14 support 1 contradict 1 tested null 2 mixed · 18 sources, 15 independent groups

What the evidence shows

IF/TRE reduces body weight vs ad libitum eating - well-supported across meta-analyses. (But see the matched-calorie comparison: the benefit is largely 'eating less', not a timing effect.)

Cochrane has no ruling yet see how our grade compares ▾

Cochrane review 2026 · low overall Not directly comparable

moderate for IF vs no intervention (weight loss), low for IF vs regular dietary advice, very low for achieving 5% weight reduction

“IF is a potentially viable but not superior weight-loss strategy based on generally low-certainty evidence. Compared to no treatment/waiting list, intermittent fasting likely results in little to no difference in weight loss; compared to regular dietary advice it makes little to no difference in weight loss or quality of life.”

Not directly comparable: their review asks a different question or reports an outcome we do not grade, so it neither corroborates nor contradicts this claim.

What is Cochrane, and why trust it?

Cochrane produces systematic reviews: instead of running a new study, they gather every trial ever done on a question, judge how well each was run, and pool the results. They take no commercial or industry funding, which is why the medical community treats their reviews as a gold standard — and why we check our own verdicts against theirs.

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The evidence (18)

Source	Grade	Stance	Quality	Finding
Mahajan A et al 2026 · study_type: RCT	RCT	supports	low	12wk pilot, n=10 T2DM women: intervention (lacto-veg diet + 10h TRE) -3.96% weight vs usual-diet control 'no meaningful changes'
(IF SR/MA) 2025 · Sleep Med Rev	meta-analysis	supports	moderate	18 RCTs: IF lowered weight/BMI/fat/waist vs ad libitum ⚠️ correction-on-file (Crossref) - kept, corrigendum not retraction
Farahmand Khoshkebijari A et al 2026 · study_type: RCT	RCT	supports	low	20 obese males, 8wk RCT: 4:3 IF+resistance-training group lost ~2x more weight/fat than regular-diet(ad-lib)+RT control group, p<0.05
Hamsho 2025 · Nutr Metab Cardiovasc Dis	meta-analysis	tested-null	moderate	Isocaloric IF not superior to calorie restriction for anthropometrics; weight loss attributable to energy deficit not timing.
Erim B et al 2026 · Research Square	observational	contradicts	moderate	n=58 adults, Ramadan TRE vs comparison group: no significant time/group/interaction effect on body weight (p>0.05), effect sizes trivial
Xing 2026 · Nutrients	meta-analysis	supports	moderate	Age-specific MA: IF improved body composition & cardiometabolic markers in healthy & overweight/obese adults.
Siles-Guerrero 2024 2024 · Nutrients	meta-analysis	supports	moderate	Fasting-based strategies vs continuous caloric restriction: similar short/long-term weight loss in obese adults.
Khalafi 2025 · Obes Rev	meta-analysis	supports	high	Long-term (>=6mo) IF reduced body weight (-2.84kg) & BMI vs control diets in overweight/obese adults.
Garegnani 2026 · Cochrane Database Syst Rev	meta-analysis	mixed	high	Cochrane review: IF for overweight/obesity shows inconsistent, often modest weight effects; uncertainty vs other diets.
Veloso NC et al 2026 · bioRxiv	animal	supports	moderate	Lactating rats: IF and CR both reduced body/adipose weight vs ad-libitum-fed dams (postpartum d0-28); IF-specific magnitude not isolated from CR arm
Sun 2025 · Int J Behav Nutr Phys Act	meta-analysis	supports	high	TRE alone vs no-restriction significantly decreased body weight (-1.59kg), fat mass, BMI, waist circumference.
Semnani-Azad 2025 2025 · BMJ	meta-analysis	supports	high	Network MA: IF vs ad-libitum reduced body weight & cardiometabolic markers; broadly comparable to continuous energy restriction. ⚠️ correction-on-file (Crossref) - kept, corrigendum not retraction
Zhang 2025 · BMC Endocr Disord	meta-analysis	supports	moderate	In metabolic syndrome, IF reduced obesity indices & improved glucolipid metabolism vs continuous energy restriction.
(BMJ network MA) 2025 · BMJ	meta-analysis	supports	moderate	Network MA: IF variants lower weight vs ad libitum; ~equivalent to continuous calorie restriction head-to-head
Xu L et al 2026 · study_type: animal	animal	supports	moderate	Overweight female cynomolgus monkeys: 20h-fast/4h-feed IF vs ad-libitum/standard-fed controls, significant body-weight reduction by day126 (p=0.0421)
Harer CM et al 2026 · study_type: animal	animal	mixed	low	Female C57BL/6J mice: fasting-mimicking-diet cycles vs ad-libitum-chow control group, bodyweight significantly decreased after fasting (vs control)
Chen 2024 · BMC Med	meta-analysis	supports	moderate	Umbrella+network MA: all IF forms improve metabolic health & reduce weight; superiority over CER unclear.
Wang B et al] # corrected 2026-08-17 from PubMed; was [(IF body-comp SR/MA) 2025 · Nutr J	meta-analysis	supports	moderate	IF improved body composition & cardiometabolic vs control

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