The Fasting-Mimicking Diet (FMD) and Cancer: What Is the Evidence?

The fasting-mimicking diet (FMD) is being studied as a possible therapy to use alongside cancer treatment. Early research shows it may lower some side effects from chemotherapy and help the body respond better to treatment. 

This article was written in partnership with KNOW Oncology. 

What is the fasting mimicking diet?

The fasting-mimicking diet (FMD) is a short-term eating plan that creates some of the effects of fasting while still giving the body some calories and important nutrients. It is eaten in repeated intervals. Usually, fewer calories are eaten 4-5 days in a row, using meals that are low in carbohydrates and protein but higher in healthy fats. This approach helps limit certain pathways in the body that react to nutrients. By doing this, the diet may improve the cells’ ability to handle stress, support cell cleanup (autophagy), and give similar health benefits to water-only fasting, but in a safer and more manageable way.

What are the potential benefits of a fasting-mimicking diet?

Human studies of the fasting-mimicking diet (FMD) have looked at using it alongside chemotherapy in patients with breast cancer. 

• Consistently, the FMD was linked to lessening several chemotherapy-related side effects, such as vomiting, nausea, low neutrophil white blood count, fatigue, and insomnia. It also may improve quality of life.¹Bahrami A, Haghighi S, Moghani MM, Khodakarim N, Hejazi E. Fasting mimicking diet during neo-adjuvant chemotherapy in breast cancer patients: a randomized controlled trial study. Frontiers in Nutrition. 2024 Dec 4:11:1483707; Lugtenberg RT, de Groot S et al. Quality of life and illness perceptions in patients with breast cancer using a fasting mimicking diet as an adjunct to neoadjuvant chemotherapy in the phase 2 DIRECT (BOOG 2013-14) trial. Breast Cancer Research and Treatment. 2021;185(3):741-758.
• The FMD may also help lower high blood glucose and C-reactive protein (a marker of chronic inflammation) as well as improve red blood cell levels.²Bahrami A, Haghighi S, Moghani MM, Khodakarim N, Hejazi E. Fasting mimicking diet during neo-adjuvant chemotherapy in breast cancer patients: a randomized controlled trial study. Frontiers in Nutrition. 2024 Dec 4:11:1483707.
• The FMD may also help the body respond better to chemotherapy, including living longer than those who do not follow this diet.³Ligorio F, Lobefaro R et al. Adding fasting-mimicking diet to first-line carboplatin-based chemotherapy is associated with better overall survival in advanced triple-negative breast cancer patients: A subanalysis of the NCT03340935 trial. International Journal of Cancer. 2024 Jan 1;154(1):114-123; de Groot S, Lugtenberg RT 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 Jun 23;11(1):3083.

Key elements of the FMD used in studies

• Plant-based, low-protein, and low-carbohydrate diet
• Strict restriction of calories, such as:
  • 600-1200 calories on day one
  • 200-500 calories on subsequent days
  • Small snacks and meals as a behavioral nutrient pattern
• Meals are made up of prepared soups, broths, nutrition bars, liquids, and tea.
• Some also included 2 grams a day of an omega-3 supplement.
• The diet is eaten for 4-5 days around each chemotherapy cycle, starting 3 days before chemotherapy begins, and is repeated with every cycle.
• A health professional monitors the patient to help them stick to the diet and make it more tolerable.
• Some naturopathic physicians recommend using a sugar-free (sweetened with stevia or xylitol) electrolyte drink once a day on fasting days to help manage hydration and energy. Sucralose-sweetened beverages are not recommended. 

It is important to note that this diet is very specific, and is intentionally designed to be followed short term. There are paid services that deliver meals specific for the FMD, such as Prolon. The diet is intended to be supervised by a clinician, even if the meals are purchased through a service. An ND or nutritionist can also provide guidance on preparing the FMD at home, which can be just as effective as a prepared kit.  

Is the FMD safe?

Before beginning any new health intervention, consult your healthcare provider. Fasting is not recommended for people at risk for malnutrition or who have a history of disordered eating. 

The most common reported side effects are low blood sugar, malnutrition, electrolyte imbalances (imbalances in the body’s minerals such as sodium, calcium, and potassium), and lower ability to put up with and stick with chemotherapy.

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