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 0.86

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

13 support 1 contradict 1 tested null 1 mixed · 16 sources, 14 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, Muley A 2026 · Nutrition and health	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'
Yong YN, McCubbin AJ, O'Driscoll DM, St-Onge MP, Bonham MP 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, Ebrahimi M, Jorbonian A 2026 · Journal of obesity	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 M, Shkorfu W, Ranneh Y, Fadel A 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 K, Liu R, Peng S, Zi X, Lian L, Yang B, Cen Y, Li Y, Zhao Y, Zhang Y 2026 · Nutrients	meta-analysis	supports	moderate	Age-specific MA: IF improved body composition & cardiometabolic markers in healthy & overweight/obese adults.
Siles-Guerrero V, Romero-Márquez JM, García-Pérez RN, Novo-Rodríguez C, Guardia-Baena JM, Hayón-Ponce M, Tenorio-Jiménez C, López-de-la-Torre-Casares M, Muñoz-Garach A 2024 · Nutrients	meta-analysis	tested-null	moderate	Inclusion required 'the control group underwent continuous calorie restriction' — no ad-libitum comparator anywhere. Short-term 9 RCTs n=565: −0.94 kg [95% CI −1.58, −0.31], p=0.004 favouring fasting (authors: not clinically significant); long-term 5 RCTs n=423: 0.06 kg [−0.98, 1.09], p=0.34. Evidence for an IF-vs-CCR claim, not IF-vs-ad-lib.
Khalafi M, Maleki AH, Ehsanifar M, Symonds ME, Rosenkranz SK 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 LI, Oltra G, Ivaldi D, Burgos MA, Andrenacci PJ, Rico S, Boyd M, Radler D, Escobar Liquitay CM, Madrid E 2026 · Cochrane Database Syst Rev	meta-analysis	supports	moderate	Comparison IF vs no intervention or waiting list (the ad libitum comparator), percentage weight loss from baseline: 'MD -3.42, 95% CI -4.95 to -1.90; 6 studies, 427 participants; moderate-certainty evidence due to risk of bias'. The interval excludes zero, so the DIRECTION of the claim is established; the authors judge the size against their own minimal important difference: 'intermittent fasting likely results in little to no difference in percentage weight loss from baseline'. Recorded as a small, real decrease (supports, moderate), not a null (cultivar ruling 2026-09-25: CONVENTIONS §5 applies to null findings, not to precise small effects). 22 RCTs overall, 1995 participants, follow-up up to 12 months; abstract only.
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 Y, Liu Y, Ye W, Lebaka VR, Chenji V, Li W, Korivi M 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 Z, Khan TA, Chiavaroli L, Chen V, Bhatt HA, Chen A, Chiang N, Oguntala J, Kabisch S, Lau DC, Wharton S, Sharma AM, Harris L, Leiter LA, Hill JO, Hu FB, Lean ME, Kahleová H, Rahelic D, Salas-Salvadó J, Kendall CW, Sievenpiper JL 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 S, Sun B, Sun L, Zou S, Chen Q 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, Guo L, Su Q, Shao Q, Lu Y, Nie Y, Yang Y, Sun Q 2026 · Journal of advanced research	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, Boulgaropoulos B, Ehall B, Bogensperger L, Bounab K, Pernitsch D, Franz J, Herbsthofer L, Kotzbeck P, Krstic J, Prokesch A, Prietl B, Kolb D, Pieber TR 2026 · FASEB journal : official publication of the Federation of American Societies for Experimental Biology	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 YE, Tsai HL, Tu YK, Chen LW 2024 · BMC Med	meta-analysis	supports	moderate	Umbrella review + NMA of 'Ten of the best and non-redundant meta-analysis studies' (153 trials, 9846 participants): vs usual diets all IF forms reduced body weight ('range of mean difference: − 0.38 to − 4.83 kg'), low/very-low certainty. Units are meta-analyses — review, zero weight.
Wang B, Wang C, Li H 2025 · Nutr J	meta-analysis	supports	moderate	IF improved body composition & cardiometabolic vs control

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