Diets · Metabolic & Cardiometabolic
intermittent fasting decreases insulin resistance
Strong support Diets 🔬 Includes disconfirming🔎 Limited evidence — fewer than 12 studies
Part of: 🥗 intermittent fasting
RefutedContestedStrong support
consensus score 0.77
📅 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
7 support 0 contradict 1 tested null 2 mixed · 10 sources, 7 independent groups
What the evidence shows
Intermittent fasting reduces insulin resistance (and weight/glucose) in PCOS.
The evidence (12)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| 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 | supports | moderate | Short-term FBS vs continuous caloric restriction: HOMA-IR 5 RCTs n=209, MD -0.14 [95% CI -0.27,-0.01], p=0.04 favouring fasting (abstract states p=0.02 for the same estimate); fasting insulin 4 RCTs n=179, p=0.02 (-7.46 pmol/L); fasting glucose (6 RCTs n=421) and HbA1c (3 RCTs n=199) null. Obese adults, not PCOS. The caloric deficit is matched by design, so this is the harder test and fasting still won the insulin endpoints. |
| Xu L, Guo L, Su Q, Shao Q, Lu Y, Nie Y, Yang Y, Sun Q 2026 · Journal of advanced research | animal | supports | moderate | 20h fast/4h feed IF x84d, overweight cynomolgus monkeys n=8/grp; insulin resistance reduced day126 p=0.0004, sustained after refeeding |
| Abu Suilik H, Farid Gadelmawla A, Rifai M, Alhawi M, Ashour A, Abdalshafy H, Abdullah Bataineh O, Rezq H, Bani Hani A, Elkhattib I, Abuelazm M 2026 · Clinical nutrition ESPEN | meta-analysis | supports | moderate | Network MA, 19 RCTs n=1149 MASLD; ADF only regimen to significantly improve HOMA-IR (direction not fully quantified in abstract) |
| Lu L, Chen X, Liou S, Weng X 2025 · J Health Popul Nutr | meta-analysis | supports | high | GRADE MA: IF favorable on IR/inflammation in MetS but controversial, limited certainty |
| Li H, Li T 2026 · Front Nutr | meta-analysis | tested-null | low | SR/MA of 9 RCTs (n=894) in MASLD, IF (6 TRF, 1 ADF, 3 5:2) vs continuous energy restriction. HOMA-IR MD -0.15 (95% CI -1.05 to 0.75; k=7; I2 81.7%; GRADE very low); fasting insulin MD +2.09 uIU/mL (-0.32 to 4.50; k=5); fasting glucose MD 0.03 mmol/L (-0.15 to 0.21). Null against an active comparator that itself lowers insulin resistance, so it bears on IF beyond CER rather than on whether IF lowers IR; MASLD, not PCOS. |
| Caretto A, Zanardini A, Frontino G, Pedone E 2026 · Nutrients | observational | supports | low | Narrative review states IF improves IR 'primarily via weight loss and gut microbiota modulation'; no effect-size given |
| Ranneh Y, Hamsho M, Shkorfu W, Terzi M, Fadel A 2025 · Nutrients | meta-analysis | supports | moderate | Pooled (5 trials): IF reduced HOMA-IR −0.94 (p<0.0001), fasting insulin −3.17 µU/mL, FBG −2.86 mg/dL, weight −4.25 kg, BMI −2.05. |
| MacKewn A et al 2026 · Research Square | RCT | mixed | low | 3-arm pre-post 30d, n=79 (IF-only n=16); combined keto+IF > IF-alone on HbA1c reduction, t(30)=2.141,p=.041; no IF-vs-no-IF control HOMA-IR reported |
| An W, Chen F, Wang B, Zhou S, Jiang L, An B, Cui Z, Ou X, Huang W, Yan H 2026 · Frontiers in endocrinology | observational | supports | low | 12wk 5:2 IF+meal-replacement, obese PCOS n=90 (PSM); HOMA-IR decreased significantly, P=0.008 |
| Yuan X, Wang J, Yang S, Gao M, Cao L, Li X, Hong D, Tian S, Sun C 2022 · Int J Endocrinol | meta-analysis | supports | moderate | Meta-analysis of intermittent-fasting trials: HOMA-IR -0.31 (95% CI -0.44 to -0.19), fasting glucose -0.15 mmol/L (-0.23 to -0.06), insulin -13.25 uIU (-16.69 to -9.82). CAVEAT: BMI (-0.8 kg/m2), weight (-1.87 kg) and waist (-2.08 cm) all fell too, so the insulin-resistance benefit is plausibly weight-mediated rather than a fasting-specific effect. |
| Jiao M, Yan H, Zhang B, Zhao X, Li J, Harun MT 2026 · Frontiers in nutrition | meta-analysis | mixed | moderate | Multilevel MA, 65 RCTs n=3293 adults; EX+IF improved fasting insulin and HOMA-IR vs controls |
| Søndergaard AM, Kjærulff MLG, Gormsen LC, Søndergaard E 2026 · American journal of physiology. Cell physiology | observational | mixed | low | Mini-review of TRE RCTs/meta-analyses: effects on insulin sensitivity 'generally small, variable, and context dependent' |
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