Intermittent Fasting Knowledge Center

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Articles592 Women107 Prolonged Fasting125 Q&As20 Unanswered85 Research Papers77 Book

Research Papers

77 peer-reviewed studies

Plain-English summaries of real clinical research on intermittent fasting and prolonged fasting, sourced from PubMed.

Research
Does Intermittent Fasting Deplete Iron, Zinc, and Vitamin D? What the Research Shows
A review of religious and intermittent fasting research finds mixed effects on iron, zinc, magnesium, and vitamin D status — here's what the evidence says.
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A 3-Day Fast Raised Resting Metabolism by 14%, Not Lowered It: What the Research Shows
A landmark study measured resting energy expenditure by indirect calorimetry during a 72-hour fast in 9 adults and found metabolism rose, not fell — driven by norepinephrine.
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Ramadan Fasting Lowers Insulin and Improves Insulin Sensitivity in Healthy Men: What the Research Shows
A 2021 American Journal of Lifestyle Medicine study (n=27 healthy men) found Ramadan fasting cut insulin and HOMA-IR, improving insulin sensitivity.
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Early Time-Restricted Eating Improved Glucose Control in a CGM Crossover Trial: What the Research Shows
A randomized crossover trial using continuous glucose monitors found early time-restricted eating improved glycemic variability in men with overweight, 2020 study.
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336 Adults Show Lower Depression and Anxiety Scores After 4 Weeks of Dawn-to-Dusk Fasting: What the Research Shows
A 2026 prospective cohort of 336 adults found PHQ-9 depression and GAD-7 anxiety scores both dropped significantly after four weeks of dawn-to-dusk intermittent fasting.
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Ramadan Fasting Doesn't Worsen Asthma in 120 Patients: What the Research Shows
A 2022 cohort study of 120 asthma patients found Ramadan fasting did not significantly change FEV1, FVC, or asthma severity — and may be safe for stable asthma.
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Intermittent Restriction Beats Continuous Dieting for Insulin Sensitivity in Overweight Women: What the Research Shows
A 107-woman RCT published in International Journal of Obesity (2011) found 5:2-style fasting matched continuous dieting for weight loss but produced greater improvements in insulin resistance.
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Intermittent Fasting Significantly Reduces Blood Sugar, Insulin, and BMI: What a 12-Study Meta-Analysis Found
A 2019 meta-analysis of 12 RCTs (870 participants) found intermittent fasting significantly reduced fasting glucose, HbA1c, fasting insulin, and BMI versus controls.
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Caloric Restriction Increases Muscle Mitochondrial Biogenesis in Humans via SIRT1 and PGC-1α: What the Research Shows
A 6-month RCT in 36 overweight adults found 25% caloric restriction raised muscle mitochondrial DNA ~35% and boosted SIRT1 and PGC-1α — the fasting energy pathway. PLoS Medicine, 2007.
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Intermittent Fasting and Ovarian Reserve in Women: What the Research Shows on AMH and Reproductive Hormone Safety
A 2022 Nutrients review of 14 human trials found intermittent fasting does not disrupt reproductive hormones in healthy women and may benefit women with PCOS.
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Calorie Restriction Activates Mitochondrial Renewal in Human Muscle: What the Research Shows
A randomised trial with muscle biopsies found 6 months of calorie restriction significantly raised PGC-1α, SIRT1, TFAM, and mtDNA in skeletal muscle — the molecular fingerprint of mitochondrial renewal.
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Alternate Day Fasting Cuts LDL by 25% and Triglycerides by 32% in 8 Weeks: What the Research Shows
A randomized trial in Am J Clin Nutr (n=16) found alternate day modified fasting reduced LDL cholesterol 25%, triglycerides 32%, and systolic blood pressure over 8 weeks.
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Intermittent Fasting Improved Cognitive Function in Older Adults with Mild Cognitive Impairment Over 3 Years: What the Research Shows
A 3-year RCT in Nutrients (2020, n=99) found 5:2 intermittent fasting significantly improved cognitive scores and reduced oxidative stress in older adults with MCI.
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Ramadan Intermittent Fasting Reduces Psoriasis Severity and Inflammatory Markers: What the Research Shows
A 2022 prospective study in Nutrients (n=41) found that 29-day Ramadan fasting reduced PASI scores by 24% and lowered TNF-α in stable plaque psoriasis patients.
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Prolonged Fasting Protected White Blood Cells and Reduced Side Effects in a Human Pilot Study: What the Research Shows
A 2009 Aging pilot study with 10 cancer patients showed that fasting 24–140 hours protected white blood cells and significantly reduced side effects, with no adverse fasting events.
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Eating Later Relative to Your Body Clock Independently Predicts Higher Body Fat: What the Research Shows
A 2017 Current Biology study (n=110) found meal timing relative to personal melatonin onset predicted body fat independently of total calorie intake, sleep, and activity.
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Daytime Eating Prevents Glucose Intolerance in Shift Workers: What the Research Shows
A 2021 Science Advances randomized crossover trial (n=12) found that restricting eating to daytime hours prevented the glucose intolerance caused by simulated night shift work.
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Alternate Day Fasting Combined with Exercise Reduced Body Fat More Than Either Approach Alone While Preserving Muscle: What the Research Shows
A 12-week randomized trial in Obesity (2013) of 64 obese adults found combining alternate day fasting with aerobic exercise preserved lean mass while cutting fat by up to 6 kg.
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Circadian Misalignment Raises Blood Pressure and Impairs Glucose Tolerance in Shift Workers: What the Research Shows
A landmark PNAS 2009 study by Scheer et al. (n=10) showed that circadian misalignment — simulated shift work — raised blood pressure, impaired glucose, and disrupted leptin within days.
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Research
Most Adults Eat Across 15 Hours a Day — and a 10-Hour Eating Window Changed Everything: What the Research Shows
A 2015 Cell Metabolism study tracked 156 adults and found most ate for 15+ hours daily. A 10-hour TRE window reduced weight 3.7% in 16 weeks without calorie counting.
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Alternate Day Fasting Combined With Exercise Preserves Lean Mass While Losing Fat: What the Research Shows
An 8-week RCT (n=64) found combining alternate day fasting with aerobic exercise reduced fat mass by 3kg while fully preserving lean body mass — outperforming either approach alone.
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Ramadan Fasting Reduces Blood Pressure, Cholesterol, and Blood Sugar: What the Research Shows
A prospective study of 82 adults found Ramadan fasting significantly reduced blood pressure, LDL cholesterol, triglycerides, and fasting glucose over one month. Nutrition Journal, 2012.
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Periodic Fasting Linked to 61% Lower Risk of COVID-19 Hospitalization or Death: What the Research Shows
A 2022 BMJ Nutrition cohort of 205 patients found periodic fasters had 11.0% vs 28.8% COVID-19 hospitalization or mortality rate (HR 0.61, p=0.013) in the pre-vaccine era.
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Early Time-Restricted Eating Reduces Appetite and Increases Fat Burning Without Lowering Metabolism: What the Research Shows
A 2019 crossover RCT in Obesity (n=11 men) found eTRE significantly cut daily appetite and boosted fat oxidation while leaving total energy expenditure unchanged.
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OMAD Does Not Suppress Resting Metabolic Rate: What the Research Shows
A randomized crossover trial in AJCN (2007, n=15) found that eating one meal per day reduced body fat without lowering resting metabolic rate or lean mass. Here's what it means.
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Early Time-Restricted Eating Improves 24-Hour Glucose Control Without Calorie Cutting: What the Research Shows
A 2019 randomized crossover trial of 15 men used CGM to show early TRE (9h window, 8am–5pm) significantly reduced 24-hour mean glucose without restricting calories.
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Research
Alternate-Day Calorie Restriction Reduces Oxidative Stress and Inflammation in Humans: What the Research Shows
A landmark 8-week pilot study in Free Radical Biology and Medicine found that alternate-day calorie restriction reduced oxidative stress markers, inflammation, and improved asthma in overweight adults.
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Alternate Day Fasting Shifts LDL to Safer, Larger Particles — Even Without Calorie Counting: What the Research Shows
British Journal of Nutrition pilot study, n=16 obese adults, 8 weeks alternate day fasting: LDL-C fell 25%, triglycerides 32%, and LDL particles shifted to larger, less atherogenic size.
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Research
Eating Protein and Vegetables Before Carbs Cut Blood Sugar Spikes by 37%: The Food Order Study
A 2015 Diabetes Care study found that eating protein and vegetables before carbohydrates reduced post-meal glucose by up to 37% and lowered insulin in adults with type 2 diabetes.
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Alternate-Day Fasting Shifts Fuel Burning Toward Fat Without Slowing Metabolism: What the Research Shows
Lean mass preserved, fat oxidation spiked, and metabolism held steady during 22 days of alternate-day fasting in 16 nonobese adults. Obesity Research, 2005.
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Alternate Day Fasting Raises Adiponectin by 29% and Reduces Leptin in Normal-Weight Adults: What the Research Shows
12-week Obesity journal RCT (n=16) found alternate day fasting raised adiponectin 29%, cut leptin 40%, reduced LDL 25% and triglycerides 31% in normal-weight adults. 2010.
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Fasting Mimicking Diet Reduces MS Symptoms and Promotes Remyelination: What the Research Shows
A 2016 Cell Reports pilot RCT (n=60 RRMS patients) found a 3-day monthly FMD improved quality of life and triggered immune cell renewal — with striking remyelination in mouse models.
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16:8 Fasting Reduces Body Fat and Visceral Fat in Older Men — While Preserving Muscle Mass: What the Research Shows
16:8 fasting for 6 weeks cut body weight 1.92 kg and visceral fat 0.64 L in overweight men aged 65–74 while fully preserving skeletal muscle (Scientific Reports, 2022).
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Research
Time-Restricted Eating and Lean Mass Loss: What the TREAT Trial Shows About Muscle Preservation
The TREAT trial (JAMA Intern Med 2020, n=116, 12 weeks) found TRE did not outperform control for weight loss and caused greater lean mass loss — with key implications for aging.
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Eating the Same Calories at Breakfast vs Dinner Produces 2.4 Times More Weight Loss: What the Research Shows
RCT of 93 overweight women eating 1,400 kcal showed big breakfast vs big dinner led to 8.7 vs 3.6 kg weight loss and a 33% triglyceride drop in 12 weeks (Obesity, 2013).
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Fasting Halved Joint Tenderness in Rheumatoid Arthritis Patients: What the Research Shows
A Lancet RCT (n=53) found that a 7–10 day fast followed by a vegetarian diet significantly improved all objective RA disease measures. Here's what the 1991 study found and what it means if you fast.
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Research
Early Time-Restricted Eating Improves Blood Sugar and Resets Circadian Clock Genes: What the Research Shows
A randomized crossover trial in Cell Metabolism (2019, n=11) found a 5-hour early eating window lowered 24h glucose, reduced oxidative stress, and upregulated autophagy and clock gene markers.
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Nightly Fasting Under 13 Hours Linked to 36% Higher Breast Cancer Recurrence: What the Research Shows
A 2016 JAMA Oncology prospective study of 2,413 breast cancer survivors found nightly fasting under 13 hours raised recurrence risk 36% and elevated HbA1c. Key findings explained.
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Research
16:8 Intermittent Fasting Significantly Improves Quality of Life and Reduces Fatigue: What the Research Shows
A 3-month prospective trial (n=30, Nutrients 2022) found 16:8 fasting significantly reduced fatigue (FAS p=0.002) and improved quality of life in healthy adults.
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Research
Intermittent Fasting vs Calorie Restriction Over 12 Months: What the Research Shows
A Norwegian 12-month RCT (n=112) compared 5:2 intermittent fasting to continuous calorie restriction. Both produced similar weight loss — and similar adherence rates. Nutrition Metab Cardiovasc Dis 2018.
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Research
Nightly 14-Hour Fasting Improves Sleep in Adults with Memory Decline and Obesity: What the Research Shows
A 2024 randomized pilot trial (n=58) found 14-hour nightly fasting significantly improved sleep quality vs health education in adults with memory decline and obesity.
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Fasting Mimicking Diet Improves Skin Hydration and Prevents Skin Roughening in Women: What the Research Shows
A 2023 RCT in 45 women showed 3 monthly cycles of a 5-day fasting mimicking diet significantly improved skin hydration and maintained skin texture vs. controls.
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Research
Intermittent Fasting Plus Resistance Training Reduces Fat While Preserving Muscle: What the Meta-Analysis Shows
A 2021 meta-analysis of 6 RCTs (n=149) in J Strength Cond Res found IF combined with resistance training significantly reduces fat mass while preserving lean mass.
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Research
Ramadan Fasting Reduces Inflammatory Cytokines by Up to 78% in Healthy Adults: What the Research Shows
A 50-person prospective study in Nutrition Research (2012) found Ramadan fasting slashed IL-1β by 78%, IL-6 by 57%, and TNF-α by 66% in healthy volunteers.
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Ramadan Fasting Increases Beneficial Gut Bacteria by Up to 73% in 30 Days: What the Research Shows
A 2021 AJCN study of 37 adults found 30 days of Ramadan intermittent fasting increased Lachnospiraceae by 61% and Ruminococcaceae by 73% — but effects reversed post-fast.
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Research
16:8 Time-Restricted Feeding Cut Crohn's Disease Activity by 40% in 12 Weeks: What the Research Shows
A 2026 Gastroenterology RCT (n=35) found 16:8 TRF for 12 weeks reduced Crohn's disease activity by 40%, cut abdominal pain by 50%, and lowered systemic inflammation.
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5:2 Intermittent Fasting Reduces Liver Fat, ALT, and Inflammation in NAFLD: What the Research Shows
A 12-week RCT in 44 NAFLD patients found 5:2 fasting cut liver steatosis (CAP −23 dB/m), ALT by 31%, and triglycerides by 25% vs control. Frontiers in Nutrition, 2022.
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Research
Fasting-Mimicking Diet Reduces IGF-1, Body Fat, and Disease Risk Markers: What the Research Shows
A 2017 randomized trial in 100 adults found three monthly FMD cycles reduced IGF-1, body fat, blood pressure, and cardiovascular risk markers while fully preserving lean mass.
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4-Hour and 6-Hour Time-Restricted Feeding Reduces Weight and Insulin Resistance Without Counting Calories: What the Research Shows
A 2020 Cell Metabolism RCT (n=58, 10 weeks) found that eating in a 4- or 6-hour daily window significantly reduced body weight, fat mass, and insulin resistance in adults with obesity — without calorie counting.
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Intermittent Fasting Increases Telomere Length in Young Women: What the Research Shows
A 2024 RCT in Biomedicines (n=29) found Ramadan intermittent fasting combined with exercise significantly increased telomere length and reduced TNF-α vs exercise alone.
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When You Eat Changes Your Stress Hormones: What the Research Shows
A 2021 Nutrients systematic review of 14 studies found that the timing of your eating window — not just fasting itself — determines how cortisol and melatonin respond to TRE.
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Time-Restricted Eating Improved Thyroid Function in Metabolic Syndrome: What the Research Shows
A 2024 randomized trial (n=162) found 8-hour TRE improved T4 levels and the T3/T4 ratio in adults with metabolic syndrome over 3 months. BMC Medicine.
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Fasting Increases Growth Hormone Secretion Up to 5-Fold in Men: What the Research Shows
A landmark Journal of Clinical Investigation study in 9 healthy men showed a 5-day fast amplified GH pulse frequency and amplitude up to 5-fold while IGF-1 fell. Here's what that means.
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Fasting Improves Mood, Sleep, and Well-Being in 1,422 People: What the Research Shows
A 2019 prospective study of 1,422 adults found supervised Buchinger fasting consistently improved mood, sleep, and overall well-being — even across 4–21 day fasts.
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16:8 Time-Restricted Eating Reduces Testosterone by 17% in Men — But Muscle Is Preserved: What the Research Shows
A 12-month RCT in Moro et al. (2021) found TRE reduced testosterone ~17% in resistance-trained men but preserved muscle and dramatically improved inflammatory markers. n=20.
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Fasting Reduces Anxiety and Depressive Symptoms Without Increasing Fatigue: What the Research Shows
A 2021 meta-analysis of 11 studies and 1,436 participants found fasting significantly reduced anxiety and depression vs. controls, with no increase in fatigue.
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Intermittent Fasting Preserves Muscle Gains During Resistance Training: What the Research Shows
A 2019 randomized trial in AJCN (n=40) found time-restricted feeding preserved fat-free mass and strength gains in resistance-trained females while reducing fat mass.
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Time-Restricted Eating Does Not Reduce Bone Density in Seven Trials: What the Research Shows
A 2024 Nutrients meta-analysis of 7 RCTs and 313 adults found TRE produced significant weight loss without reducing bone mineral density (MD −0.009 g/cm², p=0.328).
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Alternate-Day Fasting vs. Daily Calorie Restriction for Weight Loss and Cardiovascular Health: What the Research Shows
A 100-person JAMA Internal Medicine RCT compared alternate-day fasting vs. calorie restriction for 6 months. Both worked — but an LDL finding surprised researchers.
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Research
Intermittent Fasting Produces Similar Weight Loss to Daily Calorie Restriction: What the Research Shows
A 2018 meta-analysis of 11 RCTs (601 participants, 8–24 weeks) found intermittent fasting produces equivalent weight loss to continuous calorie restriction, with a key insulin advantage.
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Research
Does Time-Restricted Eating Improve Sleep? What 6 Randomized Trials Show
A 2024 systematic review of 6 RCTs in Frontiers in Nutrition found mixed results: TRE rarely worsens sleep, but significant improvements are also uncommon.
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Prolonged Fasting Forces the Body to Rebuild Its Immune System: What the Research Shows
A 2014 Cell Stem Cell study (n=11 cancer patients) found that 72-hour fasting triggers immune system regeneration via hematopoietic stem cell activation. Here's what it means.
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Monthly 5-Day Fasting Diet Reduces IGF-1, Body Weight, and Inflammation: What the Research Shows
A 2015 Cell Metabolism pilot RCT (n=38) found that a monthly 5-day fasting-mimicking diet reduced IGF-1 by 13%, waist circumference, blood pressure, and CRP in 3 months.
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5-Day Fasting Reshapes the Gut Microbiome and Reduces Blood Pressure: What the Research Shows
A 2021 Nature Communications study (n=71) found that a 5-day fasting protocol changed gut bacteria composition, reduced blood pressure, and improved metabolic markers in metabolic syndrome patients.
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Alternate Day Fasting Increases Autophagy and Improves Aging Markers in Healthy Adults: What the Research Shows
A 2019 Cell Metabolism RCT (n=60) found alternate day fasting measurably increased autophagy markers and improved cardiovascular aging biomarkers in healthy non-obese adults.
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Intermittent Fasting Reduces Insulin Resistance and Improves Hormone Profiles in Women with PCOS: What the Research Shows
A 2025 meta-analysis in Nutrients (PMID 40806019) found IF significantly reduced HOMA-IR by 0.94, lowered insulin 3.17 μU/mL, and raised SHBG in women with PCOS.
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Time-Restricted Eating Does Not Change Sex Hormones in Women or Men With Obesity: What the Research Shows
A 12-month randomized trial (n=90) found 8-hour TRE produced significant weight loss but left sex hormone levels unchanged in premenopausal and postmenopausal women. European Journal of Clinical Nutrition, 2024.
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Ramadan Fasting Raised BDNF by 47% and Serotonin in 29 Healthy Adults: What the Research Shows
A 2017 human study found Ramadan intermittent fasting (15+ h/day for 29 days) raised BDNF by 47%, NGF by 23%, and serotonin significantly in 29 healthy adults.
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Intermittent Fasting Slows Brain Aging and Boosts Executive Function: What the Research Shows
A 2024 Cell Metabolism RCT (n=40 older adults, 8 weeks) found 5:2 fasting reduced brain aging markers, improved executive function, and cut neuronal insulin resistance.
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Intermittent Fasting Reduces Inflammation Markers Across 21 Studies: What the Research Shows
A 2025 network meta-analysis in Nutrients pooled 839 adults across 21 trials and found IF significantly reduced TNF-alpha, CRP, and leptin — with time-restricted feeding showing the largest effect.
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16:8 Intermittent Fasting Reduces Blood Pressure and Inflammation in Trained Adults: What the Research Shows
A randomized crossover trial (n=34, 8 weeks, J Translational Medicine 2016) found 16:8 TRF significantly reduced systolic BP, inflammation markers, and fat mass while preserving muscle.
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Early Time-Restricted Eating Improves Insulin Sensitivity Without Weight Loss: What the Research Shows
A 2018 Cell Metabolism RCT (n=8) found that eating only from 6am–3pm improved insulin sensitivity, blood pressure, and oxidative stress in men with prediabetes — without any weight loss.
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8-Hour Eating Window Improves Blood Sugar Control in Metabolic Syndrome: What the Research Shows
A 2024 RCT in Annals of Internal Medicine (n=108) found that time-restricted eating significantly improved HbA1c and cardiometabolic markers in metabolic syndrome patients.
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Alternate Day Fasting Reduced Liver Fat by 5.48% in 3 Months: What the Research Shows
A 2023 Cell Metabolism RCT found alternate day fasting combined with exercise reduced liver fat 32x more than controls in 3 months, without muscle loss. Here is what the study found.
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Research
10-Hour Time-Restricted Eating Reduces Weight, Blood Pressure, and Cholesterol in Metabolic Syndrome: What the Research Shows
A Cell Metabolism 2020 pilot study of 19 adults with metabolic syndrome found 12 weeks of 10-hour TRE reduced body weight, blood pressure, and atherogenic lipids without changing diet.
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Research
Intermittent Fasting Outperforms Daily Calorie Restriction for Blood Sugar Control: What the Research Shows
A 2023 Nature Medicine RCT (n=209) found that intermittent fasting with early time-restricted eating improved glucose tolerance significantly more than daily calorie restriction at 6 months.
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Time-Restricted Eating Did Not Significantly Outperform Calorie Restriction Alone at 12 Months: What the Research Shows
NEJM 12-month RCT (n=139): adding an 8-hour eating window to calorie restriction produced similar weight loss to calorie restriction alone — but both groups lost significant weight.
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