Fasting-mimicking diet
In trials, monthly 5-day fasting-mimicking cycles lowered weight, HbA1c and blood pressure against usual diets, and one 12-month trial in type 2 diabetes cut glucose-lowering medication. Single trials report better Crohn's disease response and breast tumor response to chemotherapy. Serious side effects were rare, and muscle area did not change. Lifespan has not been measured.
- Status
- A dietary pattern, also sold as a commercial 5-day meal kit. Not a regulated product.
- Also called
- fasting-mimicking diet, fasting mimicking diet, FMD, ProLon, 5-day fasting mimicking diet, periodic fasting, periodic fasting-mimicking diet
- Followed for
- weight loss, fat loss, blood sugar, type 2 diabetes, blood pressure, inflammation, Crohn's disease, cancer treatment support, biological age, longevity
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help6
- ModerateShown to lower HbA1c in pooled trials, and one 12-month trial found monthly cycles cut HbA1c 0.3% while lowering glucose-lowering medication in type 2 diabetes.
- ModerateShown to lower body weight and fat against usual diets, by 3.6 kg over 12 months in type 2 diabetes, and about as much as a Mediterranean diet.
- ModerateShown to lower systolic blood pressure by about 4 mm Hg and diastolic by about 2 mm Hg in pooled trials.
- LimitedOne open-label trial found more clinical response, 69.2% against 43.8%, and more remission after three monthly cycles in mild to moderate Crohn's disease.
- LimitedOne phase 2 trial found more tumor responses with the diet during chemotherapy before surgery, and side effects did not differ although dexamethasone was left out.
- LimitedOne secondary analysis linked three cycles to a 2.5-year drop in a blood-based estimate of biological age, with similar results in a second study.
What people follow it for, and what was found
Shown to help6
Blood sugar in type 2 diabetes
Shown to lower HbA1c in pooled trials, and one 12-month trial found monthly cycles cut HbA1c 0.3% while lowering glucose-lowering medication in type 2 diabetes.
Compared with normal diets, a meal replacement, continuous energy restriction, a Mediterranean diet, a placebo or a supplement [1]; usual care alone [2]; before the diet, in the same people [3]; before the diet in the same people, and a Mediterranean diet [4]
The numbers and sources
- Effect
- Across 11 randomized trials, HbA1c fell 8.589 mmol/mol (95% CI -12.389 to -4.769) [1]. In type 2 diabetes treated with metformin alone or diet, monthly 5-day cycles added to usual care for 12 months lowered the medication effect score by 0.3 (95% CI -0.4 to -0.2) and HbA1c by 3.2 mmol/mol, or 0.3% (95% CI -0.6 to -0.0). Glycemic management improved in 53% against 8% of controls [2]. In a 6-month trial in 40 adults with type 2 diabetes and raised urine albumin, HOMA-IR fell 3.8 from baseline after 6 monthly cycles (95% CI -5.6 to -2.0), a change within the fasting group. The trial's main outcome, the change in urine albumin, did not differ from the Mediterranean diet group [3]. In people with hypertension, HbA1c fell from baseline on cycles, and no measure differed from a Mediterranean diet at the end [4].
- Population
- 11 trials [1]; 100 adults aged 18 to 75 with type 2 diabetes and BMI 27 or more [2]; 40 adults with type 2 diabetes and raised urine albumin [3]; adults with overweight or obesity and hypertension [4].
- Sources
- [1], [2], [3], [4]
- Caveats
- The 12-month trial was co-funded by L-Nutra, and 18 of 100 participants were lost to follow-up [2]. The meta-analysis abstract does not describe the populations or heterogeneity [1].
Weight and body fat
Shown to lower body weight and fat against usual diets, by 3.6 kg over 12 months in type 2 diabetes, and about as much as a Mediterranean diet.
Compared with usual care alone [2], [6]; a continuous Mediterranean diet [4]; an unrestricted diet, in generally healthy US adults [5]
The numbers and sources
- Effect
- Three monthly cycles lowered body weight and trunk and total body fat against an unrestricted diet [5]. Over 12 months in type 2 diabetes, weight fell 3.6 kg (95% CI -5.2 to -2.1) more than usual care [2], with 37.9 cm² less visceral fat and 20.9 cm² less subcutaneous fat on MRI [6]. Against a continuous Mediterranean diet for 4 months, weight, waist, BMI and body fat fell by comparable amounts [4].
- Population
- 100 generally healthy US adults, 71 completing three cycles [5]; 100 adults with type 2 diabetes, 89 with baseline MRI [2][6]; adults with hypertension and BMI 28 or more [4].
- Sources
- [2], [4], [5], [6]
- Caveats
- The abstract of [5] gives no effect sizes. The comparisons are against usual or unrestricted diets, apart from [4].
Blood pressure
Shown to lower systolic blood pressure by about 4 mm Hg and diastolic by about 2 mm Hg in pooled trials.
Compared with normal diets, a meal replacement, continuous energy restriction, a Mediterranean diet, a placebo or a supplement [1]; an unrestricted diet, in generally healthy US adults [5]
The numbers and sources
- Effect
- Systolic pressure fell 4.148 mm Hg (95% CI -7.584 to -0.711) and diastolic 2.263 mm Hg (95% CI -4.162 to -0.364) [1]. Three cycles lowered blood pressure against an unrestricted diet [5].
- Population
- 11 trials [1]; 100 generally healthy adults [5].
- Sources
- [1], [5]
- Caveats
- Other cardiovascular risk factors did not change significantly in the pooled analysis [1].
Crohn's disease
One open-label trial found more clinical response, 69.2% against 43.8%, and more remission after three monthly cycles in mild to moderate Crohn's disease.
Compared with continuing the usual baseline diet [7]
The numbers and sources
- Effect
- After three 5-day cycles, 45 patients on the diet (69.2%) and 14 controls (43.8%) had a clinical response (P 0.03), and 64.6% against 37.5% reached clinical remission (P 0.02). Fecal calprotectin fell 22.0% against a rise of 8.0% (P 0.03) [7].
- Population
- Adults with mild to moderate Crohn's disease, with controls continuing their usual diet [7].
- Sources
- [7]
- Caveats
- Open-label, so patients knew their group, and disease activity scores include symptoms [7].
Breast cancer chemotherapy
One phase 2 trial found more tumor responses with the diet during chemotherapy before surgery, and side effects did not differ although dexamethasone was left out.
Compared with the patients' regular diet [8]
The numbers and sources
- Effect
- Complete or partial radiological response was more common on the diet (OR 3.168, P 0.039). Per protocol, a 90% to 100% tumor-cell loss was more likely (OR 4.109, P 0.016). Toxicity did not differ from the regular diet group, and chemotherapy-induced DNA damage in T cells was lower [8].
- Population
- 131 patients with HER2-negative stage II or III breast cancer, without diabetes [8].
- Sources
- [8]
- Caveats
- A phase 2 trial. The pathological result was per protocol [8].
Biological age
One secondary analysis linked three cycles to a 2.5-year drop in a blood-based estimate of biological age, with similar results in a second study.
Compared with before the diet, in the same people [9]
The numbers and sources
- Effect
- Three cycles were associated with lower insulin resistance, lower liver fat on MRI and a 2.5-year fall in median biological age on a validated measure, independent of weight loss. A second clinical study gave nearly identical results [9].
- Population
- Adult participants in a randomized trial and a second clinical study [9].
- Sources
- [9]
- Caveats
- A secondary and exploratory analysis. Biological age is an estimate from blood markers, not lifespan [9].
Not shown to help1
Kidney protein loss in diabetes
One small trial found urine albumin did not change more than on a Mediterranean diet over 6 months, with a fall only in people with microalbuminuria.
Compared with a Mediterranean diet [3]
The numbers and sources
- Effect
- Change in albumin-to-creatinine ratio was comparable between groups (P 0.45). Patients with microalbuminuria had a fall of 30.3 mg/g, and those with macroalbuminuria did not [3].
- Population
- 40 adults with type 2 diabetes and raised urine albumin [3].
- Sources
- [3]
- Caveats
- A proof-of-concept trial with a prespecified subgroup analysis [3].
Claimed, not studied in people1
Longevity
Not studied in people. Fasting-mimicking cycles started at middle age lengthened life in mice, and in prematurely aging mice, and extended yeast lifespan.
No study in people. This rests on animal studies.
The numbers and sources
- Effect
- In mice, cycles of a fasting-mimicking diet twice a month started at middle age extended longevity, lowered visceral fat and cancer incidence, and slowed bone density loss. Alternating fasting and feeding also extended yeast lifespan [11]. In prematurely aging mice, the diet significantly prolonged lifespan, and in naturally aging mice it improved cognitive and gut measures [12].
- Population
- Yeast and mice [11]. Prematurely and naturally aging mice [12].
- Sources
- [11], [12]
- Caveats
- Lifespan has not been measured in people. The biological age findings above are markers, not lifespan [9]. The diet cycles in mice differ from the 5-day monthly cycles used in human trials [5].
How trials defined it
The first trial described the diet as low in calories, sugars and protein and high in unsaturated fats [5]. Trials gave it for 5 consecutive days a month, with usual eating the rest of the month, for 3 months [5][7], 4 months [4], 6 months [3] or 12 months [2]. In breast cancer, the diet was taken for 3 days before and during each chemotherapy cycle [8]. A recipe-based version in breast cancer provided 34% to 54% of normal calorie intake for 4 days before and on the day of each chemotherapy cycle [10].
Risks
Mixed results1
Side effects
Serious side effects were not reported in trials of generally healthy adults, and grade 3 or worse effects had an incidence of 5.95% in a pilot during chemotherapy.
The numbers and sources
- Effect
- No serious adverse effects were reported over three cycles [5]. In type 2 diabetes, 71% to 95% of participants reported no adverse effects [3]. Chemotherapy toxicity did not differ from the regular diet group [8]. In a single-arm pilot during chemotherapy, the incidence of grade 3 or worse diet-related adverse effects was 5.95% (5 of 84) [10].
- Population
- 100 generally healthy adults [5]; 40 adults with type 2 diabetes [3]; 131 women with breast cancer [8]; 30 women with breast cancer, 27 completing 3 cycles [10].
- Sources
- [3], [5], [8], [10]
- Caveats
- Small trials, and the abstracts do not list which side effects occurred. The pilot had no control group [10].
Checked, no increase found1
Muscle loss
Small trials found no measurable muscle loss with monthly cycles, including abdominal muscle area over 12 months in type 2 diabetes.
The numbers and sources
- Effect
- Abdominal muscle area changed by -1.6 cm² (95% CI -4.6 to 1.4) against usual care over 12 months [6]. Muscle mass changed by -0.05 kg (95% CI -0.36 to 0.27) after 3 cycles during chemotherapy [10]. In follow-up after 4 months of cycles, the Mediterranean diet group lost fat-free mass and the fasting-mimicking group did not [4].
- Population
- 89 adults with type 2 diabetes [6]; 27 women with breast cancer [10]; adults with hypertension [4].
- Sources
- [4], [6], [10]
- Caveats
- MRI area and body composition estimates, not strength. The pilot had no control group [10].
Sources
- Mohammadzadeh M, Amirpour M, Ahmadirad H, et al. Impact of Fasting Mimicking Diet (FMD) on cardiovascular risk factors: a systematic review and meta-analysis of randomized control trials. Diabetology & Metabolic Syndrome. 2025. https://doi.org/10.1186/s13098-025-01709-5
- van den Burg EL, Schoonakker MP, van Peet PG, et al. Integration of a fasting-mimicking diet programme in primary care for type 2 diabetes reduces the need for medication and improves glycaemic control: a 12-month randomised controlled trial. Diabetologia. 2024. https://doi.org/10.1007/s00125-024-06137-0
- Sulaj A, Kopf S, von Rauchhaupt E, et al. Six-Month Periodic Fasting in Patients With Type 2 Diabetes and Diabetic Nephropathy: A Proof-of-Concept Study. The Journal of Clinical Endocrinology & Metabolism. 2022. https://doi.org/10.1210/clinem/dgac197
- Mishra A, Fanti M, Ge X, et al. Fasting mimicking diet cycles versus a Mediterranean diet and cardiometabolic risk in overweight and obese hypertensive subjects: a randomized clinical trial. npj Metabolic Health and Disease. 2023. https://doi.org/10.1038/s44324-023-00002-1
- Wei M, Brandhorst S, Shelehchi M, et al. Fasting-mimicking diet and markers/risk factors for aging, diabetes, cancer, and cardiovascular disease. Science Translational Medicine. 2017. https://doi.org/10.1126/scitranslmed.aai8700
- Schoonakker MP, van den Burg EL, van Peet PG, et al. A fasting-mimicking diet programme reduces abdominal adipose tissue while preserving abdominal muscle mass in persons with type 2 diabetes. Nutrition, Metabolism and Cardiovascular Diseases. 2025. https://doi.org/10.1016/j.numecd.2025.104111
- Kulkarni C, Fardeen T, Gubatan J, et al. A fasting-mimicking diet in patients with mild-to-moderate Crohn's disease: a randomized controlled trial. Nature Medicine. 2026. https://doi.org/10.1038/s41591-025-04173-w
- de Groot S, Lugtenberg RT, Cohen D, et al. Fasting mimicking diet as an adjunct to neoadjuvant chemotherapy for breast cancer in the multicentre randomized phase 2 DIRECT trial. Nature Communications. 2020. https://doi.org/10.1038/s41467-020-16138-3
- Brandhorst S, Levine ME, Wei M, et al. Fasting-mimicking diet causes hepatic and blood markers changes indicating reduced biological age and disease risk. Nature Communications. 2024. https://doi.org/10.1038/s41467-024-45260-9
- Xue M, Zhang N, Dong X, et al. The feasibility and safety of fasting-mimicking diet in breast cancer patients with chemotherapy in China. Breast Cancer Research and Treatment. 2025. https://doi.org/10.1007/s10549-025-07756-w
- Brandhorst S, Choi IY, Wei M, et al. A periodic diet that mimics fasting promotes multi-system regeneration, enhanced cognitive performance, and healthspan. Cell Metabolism. 2015. https://doi.org/10.1016/j.cmet.2015.05.012
- Wang Q, Xu J, Luo M, et al. Fasting mimicking diet extends lifespan and improves intestinal and cognitive health. Food & Function. 2024. https://doi.org/10.1039/d4fo00483c