Fasting has been a part of human existence for thousands of years. The simple fact during the early centuries of our existence, food was scarce which meant that we had to fast until we found food, either through hunting or foraging.
Over the centuries, fasting has been (and remains) a part of many world religions. Recently, fasting has garnered attention for its potential health and longevity benefits, particularly in regards to something called autophagy (a biological process where the body recycles and repairs damaged cells).[1]
Animal studies also indicate that fasting improve insulin sensitivity and reduce body fat, atherogenic lipids, blood pressure, and IGF-1.[2]
As you might imagine, these findings ignited interest in applying various fasting protocols to human subjects to see if similar effects manifested.
Today, we’ll discuss one of the more popular fasting protocols you’ll come across -- the fasting-mimicking diet.
What is the Fast-Mimicking Diet?
Abbreviated as FMD, the fasting mimicking diet is a plant-based, low-calorie and low-protein 5-day lasting dietary intervention) followed by a normal diet has positive effects on both cellular function and healthspan.[3]
The FMD protocol has been popularized by Dr. Valter Longo -- a professor of gerontology and biological sciences at the University of Southern California (USC) as well as the director of the USC Longevity Institute. He is well-known for his research and presentations on aging and age-related diseases.
How Does the FMD Work?
Per the human clinical studies, on day 1 of the FMD, individuals consumed ~1100 calories (11% protein, 46% fat, and 43% carbohydrate). On days 2-5, study participants consumed ~720 calories (9% protein, 44% fat, and 47% carbohydrate) per day.
After the fifth day, the study group returned to their normal diet until the next FMD cycle started (about 25 days later). This process was repeated for a total of 4 FMD cycles.[4]
Basically, once per month you eat a very low amount of calories for five straight days and then resume your normal healthy eating habits. The purported benefits of the fasting mimicking diet are to improve metabolism, reduce blood pressure and support healthy aging.
Human Studies
To date, the fasting-mimicking diet has only been studied a couple of times. One of the studies compared its effects on a variety of metabolic markers to the Mediterranean Diet, which is regarded for its cardiovascular and longevity benefits.
Both diets led to comparable decreases in weight, waist circumference, body mass index (BMI), body fat mass, body fat %, total cholesterol, and leptin.[4]
Other studies have reported improvements in AD biomarkers, cognitive functions, and subjective well-being measures following FMDs.[5]
An earlier literature review on FMD concluded that “... larger clinical trials are warranted to further investigate the efficacy of prescribed fasting regimens for the treatment of chronic lifestyle and obesity-related diseases.[6]
What Can I Eat on a Fasting-Mimicking Diet?
FMD is a low-calorie, low-protein, and high fat plant-based diet.
During your 5-day FMD, you may eat:
- Vegetable broth
- Nuts & seeds
- Legumes
- Fruits & vegetables
- Herbal teas
Supplements are allowed on the FMD, including omega-3s, amino acids, and greens powders.
How Often Can a Fasting-Mimicking Diet Be Used?
Research studies have individuals follow FMD once a month, for 3-4 months total.
Takeaway
The fasting-mimicking diet provides a framework to mimic the beneficial effects of fasting while still providing nutrients to the body. Animal studies and a handful of small human clinicals shown promise, but more rigorous trials with larger populations are warranted.
As you can guess, the FMD is primarily geared towards individuals that are trying to lose weight and/or promote longevity. Given the woefully inadequate amount of protein, FMD is not recommended for individuals trying to build/maintain lean muscle mass or in-season athletes.
FMD has not been shown to lead to superior long-term weight loss results compared to standard dieting (i.e. reducing daily calorie intake by 10-15%). As such, it may be easier for individuals to adhere to a “regular” diet as opposed to fasting once per month.
If you need help knowing how many calories to eat to get results, open up the 1UP Fitness App where we provide customized eating plans and calorie levels based on your goals and preferences.
References
- Aman, Y., Schmauck-Medina, T., Hansen, M. et al. Autophagy in healthy aging and disease. Nat Aging 1, 634–650 (2021). https://doi.org/10.1038/s43587-021-00098-4
- Secor SM, Carey HV. Integrative Physiology of Fasting. Compr Physiol. 2016 Mar 15;6(2):773-825.
- Brandhorst, S., Levine, M.E., Wei, M. et al. Fasting-mimicking diet causes hepatic and blood markers changes indicating reduced biological age and disease risk. Nat Commun 15, 1309 (2024). https://doi.org/10.1038/s41467-024-45260-9
- Mishra, A. et al. Fasting mimicking diet cycles versus a Mediterranean diet and cardiometabolic risk in overweight and obese hypertensive subjects: a randomized clinical trial. npj Metab. Health Dis. 1, 1 (2023).
- Boccardi V, Pigliautile M, Guazzarini AG, Mecocci P. The Potential of Fasting-Mimicking Diet as a Preventive and Curative Strategy for Alzheimer's Disease. Biomolecules. 2023 Jul 14;13(7):1133. doi: 10.3390/biom13071133. PMID: 37509169; PMCID: PMC10377404.
- Mattson MP, Longo VD, Harvie M. Impact of intermittent fasting on health and disease processes. Ageing Res Rev. 2017 Oct;39:46-58.
