Fasting-Mimicking Diet: What a 3-Month Trial Found
The fasting-mimicking diet means 5 low-calorie days a month. A 3-month trial with commercial ties found lower weight and blood pressure. Its limits and who should avoid it.
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Editorial review against cited sources, not medical review. Educational, not medical advice.
In 30 seconds
The fasting-mimicking diet is a 5-day plan low in calories, sugars and protein, repeated monthly in the trial cited here. In that 3-month trial in generally healthy adults, it lowered weight, body fat, blood pressure and IGF-1 compared with usual eating. The trial had commercial ties, and long-term benefits aren’t established.
- In the trial, the diet gave about 1,100 kcal on day 1 and about 720 kcal a day on days 2 to 5.
- Three monthly cycles lowered weight, trunk and total body fat, blood pressure and IGF-1 compared with eating as usual.
- The diet was supplied by its maker, and some authors held equity in that company.
What is the fasting-mimicking diet?
It’s a short, very low-calorie diet rather than a daily fasting schedule. You still eat every day, but for 5 days in a row you eat little, mostly fat and carbohydrate with little protein, and then you eat normally for the rest of the month.
In the trial, the fasting-mimicking diet supplied about 4,600 kJ (about 1,100 kcal) on day 1 and about 3,000 kJ (about 720 kcal) a day on days 2 to 5, with fat and complex carbohydrate as the main sources of energy and about 9% to 11% of energy from protein.Source 1
| Pattern | What you do | How often |
|---|---|---|
| Fasting-mimicking diet | About 720 to 1,100 kcal a day for 5 days in a row | Once a month in the trial |
| 5:2 | Two reduced-calorie days, five usual days | Every week |
| 16:8 | Eat within 8 hours, fast for 16 | Every day |
What did the trial find?
Here’s what the randomized trial did and found.
The trial randomized 100 generally healthy adults to 3 months of an unrestricted diet or to the fasting-mimicking diet for 5 consecutive days a month for 3 months; the control group then crossed over, and 71 people completed three cycles.Source 1
Compared with the unrestricted diet, three cycles reduced body weight, trunk and total body fat, blood pressure and insulin-like growth factor 1 (IGF-1).Source 1
Not everyone finished the trial, and some lean mass went along with the weight.
No serious adverse effects were reported; fatigue, weakness and headache were the most common mild or moderate symptoms, and 25% of the diet group withdrew or were excluded, compared with 10% of the control group.Source 1
Lean mass as a share of body weight did not change, although absolute lean mass fell in the diet group.Source 1
Early evidence
One 3-month trial with commercial ties
The trial measured risk markers such as blood pressure and IGF-1 in generally healthy US adults, not illness. The diet was supplied by L-Nutra, which licenses it from the authors' university; the university may receive royalties, and some authors hold equity in the company.Source 1
Blimbi doesn’t recommend any diet product. The tested diet is a proprietary formulation, and the trial didn’t compare brands or homemade versions. For daily patterns, see types of intermittent fasting.
Who should avoid it?
Frequently asked questions
Talk to a qualified health professional before fasting if you are pregnant or breastfeeding, under 18, living with or recovering from an eating disorder, have diabetes, take insulin or a medicine affected by meal timing, are an older adult, or are acutely ill. Do not change the dose or timing of any medicine without your clinician. See Blimbi’s safety guide.
Frequently asked questions
What is the fasting-mimicking diet?
A 5-day plan that is low in calories, sugars and protein, repeated monthly in the trial cited here: about 1,100 kcal on day 1 and about 720 kcal a day after that, then usual eating.Source 1
Does the fasting-mimicking diet work?
In one 3-month trial in generally healthy adults, it lowered weight, body fat, blood pressure and IGF-1 versus usual eating. It measured risk markers, not disease, and had commercial ties.Source 1
Is the fasting-mimicking diet the same as intermittent fasting?
No. Daily schedules such as 16:8 limit when you eat; this plan limits how much you eat for 5 days in a row, then you eat as usual for the rest of the month.Source 1
Sources
Fasting-mimicking diet and markers/risk factors for aging, diabetes, cancer, and cardiovascular diseaseMin Wei et al. American Association for the Advancement of Science (AAAS), February 15, 2017.DOI: 10.1126/scitranslmed.aai8700 · PMID: 28202779Human randomized trial
Overview – Eating disordersNHS. NHS, January 23, 2024.Official guidance
Fasting Safely with DiabetesMartin M. Grajower. National Institute of Diabetes and Digestive and Kidney Diseases, August 26, 2020.Official guidance
Calorie restriction and fasting diets: What do we know?National Institute on Aging. National Institute on Aging, August 14, 2018.Official guidance