Fasting Mimicking Diet Improves Weight, Waist Size, and Blood Pressure in Prostate Cancer Patients: What the Research Shows

Fasting Mimicking Diet Improves Weight, Waist Size, and Blood Pressure in Prostate Cancer Patients: What the Research Shows

Medical disclaimer: This article summarises published research for informational purposes only. It is not medical advice and is not a substitute for guidance from a qualified health professional. Always consult your doctor before starting any fasting protocol, especially if you have an existing health condition or take medication.

Study at a Glance

What This Study Looked At

Men treated for prostate cancer — particularly those on androgen deprivation therapy — often develop features of metabolic syndrome: weight gain, higher blood pressure, and worsening cholesterol and blood sugar numbers. This Irish pilot study asked a simple question: could a periodic fasting mimicking diet (FMD) — a low-calorie, low-protein, high-unsaturated-fat plan followed for just 4 days at a time — meaningfully improve those metabolic markers in men already living with prostate cancer? Unlike studies that test fasting alongside chemotherapy, this trial focused purely on metabolic health, not cancer treatment tolerability.

Who Was Studied

Participant profile: Adult men with a diagnosis of prostate cancer, many showing features of metabolic syndrome (elevated weight, waist circumference, or blood pressure) at baseline. This was a single-arm implementation study — there was no separate control group; each participant's post-intervention measurements were compared against their own baseline.

How the FMD worked in this study: Participants followed a commercially packaged 4-day fasting mimicking diet — low in calories, sugar, and protein, but relatively high in unsaturated fats — once per month for 3 consecutive months. Weight, abdominal circumference, blood pressure, and selected blood laboratory markers were measured at baseline and again 3 months after the third FMD cycle.

What the Researchers Found

Body Weight and Waist Circumference

Blood Pressure

• Three monthly 4-day FMD cycles produced measurable reductions in both body weight and waist circumference in men with prostate cancer.
• The blood pressure improvements were clinically meaningful — a nearly 10-point drop in systolic pressure is comparable to the effect seen with some antihypertensive medications.
• These changes occurred with only 12 total fasting-mimicking days spread across 3 months, not a daily restrictive diet.

What Did Not Change

The published pilot summary emphasizes weight, waist circumference, and blood pressure as its headline findings; detailed data on PSA levels, lipid panels, and glucose markers from the "selected laboratory results" were collected but not fully broken out in the publicly available abstract.

What the Researchers Concluded

The researchers concluded that a periodic 4-day fasting mimicking diet is a feasible and implementable intervention that produced measurable improvements in weight, abdominal circumference, and blood pressure in a real-world cohort of prostate cancer patients — a population at elevated risk of metabolic syndrome due to their cancer treatment.

What This Means If You Fast

• You don't need to fast every day to see metabolic benefits. This study used just 4 days per month, and still produced meaningful changes in weight and blood pressure over 3 months.
• Prostate cancer treatment and metabolic health are connected. Androgen deprivation therapy is known to drive weight gain and cardiovascular risk; this study suggests periodic fasting may help counter some of that.
• Blood pressure may respond quickly. A near 10-point systolic drop after just three short fasting cycles is a substantial change — similar patterns of fasting-related blood pressure improvement have shown up in other metabolic syndrome trials.
• This wasn't daily intermittent fasting. If a 4-day monthly FMD isn't practical for you, more familiar patterns like 16:8 time-restricted eating work through some of the same autophagy and metabolic pathways, though they haven't been tested head-to-head against FMD in this population.
• This is relevant beyond cancer patients. The metabolic improvements — less weight, smaller waist, lower blood pressure — are the same outcomes fasting protocols aim for in the general population, reinforcing that periodic fasting's benefits aren't limited to any one group.
• Talk to your oncology team first. Men undergoing active cancer treatment should always coordinate any dietary change, including fasting, with their treating physician.

Study Limitations

• Small sample size (35 enrolled, only 29 completed all three cycles)
• No control group — this was a single-arm pre/post pilot, so some improvement could reflect general lifestyle awareness rather than the FMD itself
• Short follow-up (3 months); long-term durability of the weight and blood pressure changes is unknown
• Detailed PSA, lipid, and glucose data were not fully reported in the available public abstract
• All participants were prostate cancer patients, most already showing signs of metabolic syndrome — results may not generalize to men without cancer or without baseline metabolic risk factors
• As an implementation/feasibility pilot rather than a randomized trial, it cannot establish causality as strongly as an RCT would

Source

Fay-Watt, V., O'Connor, S., Roshan, D., Romeo, A. C., Longo, V. D., & Sullivan, F. J. (2023). The impact of a fasting mimicking diet on the metabolic health of a prospective cohort of patients with prostate cancer: A pilot implementation study. Prostate Cancer and Prostatic Diseases, 26(2), 317–322. PMID: 35314788

Frequently Asked Questions

Can fasting help men with prostate cancer?

This pilot study found that 3 monthly cycles of a 4-day fasting mimicking diet reduced weight by an average of 3.79 kg and systolic blood pressure by 9.52 mmHg in prostate cancer patients, suggesting periodic fasting may help manage the metabolic side effects of cancer treatment.

What is a fasting mimicking diet?

A fasting mimicking diet (FMD) is a structured, low-calorie, low-protein, high-unsaturated-fat eating plan followed for a set number of days (4 in this study) that triggers metabolic responses similar to a full water fast while still allowing some food intake.

Does androgen deprivation therapy cause weight gain?

Yes — androgen deprivation therapy, a common prostate cancer treatment, is well known to increase the risk of weight gain, abdominal fat accumulation, and metabolic syndrome. This is part of why researchers tested a fasting intervention in this population.

How much weight did participants lose in this study?

Participants lost an average of 3.79 kg and reduced their abdominal circumference by an average of 4.57 cm after completing three monthly 4-day FMD cycles over approximately 3 months.

Is this the same as daily intermittent fasting?

No. This study used a monthly 4-day fasting mimicking diet, not a daily eating-window protocol like 16:8. The two approaches likely share some underlying mechanisms, such as reduced insulin and autophagy activation, but they have not been directly compared in this population.

Related Research and Articles

• What is 16:8 intermittent fasting?
• How intermittent fasting promotes autophagy
• 10-hour time-restricted eating and metabolic syndrome
• Time-restricted eating for metabolic syndrome: 2024 RCT
• Intermittent fasting and testosterone in men

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