Fasting before and after chemo may help improve treatment response in ovarian cancer

A new pilot study has found that fasting before and after chemotherapy sessions, when compared with regular eating, can help reduce insulin levels and may improve treatment response for women with high-grade serous ovarian cancer (HGSOC). The research was presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting.

“Despite advancements in surgery and chemotherapy, patients with advanced ovarian cancer still face poor outcomes. This highlights the urgent need for safe, low-cost, and easily implementable strategies that can enhance treatment efficacy and improve patient prognosis,” said lead study author Dr Claudia Marchetti, Fondazione Policlinico Universitario Agostino Gemelli, Rome, Italy.

This Italian pilot study looked into the impact of fasting on insulin levels and the effectiveness of chemotherapy for people with HGSOC.

It included 36 people from Rome being treated for stage III or IV HGSOC. The average age of the participants was 62, and almost all were in good general health and able to perform their usual daily tasks.

Participants received three rounds of carboplatin and paclitaxel chemotherapy before they had surgery to remove the tumours.

Before starting chemotherapy, participants were assigned randomly to either fast for 36 hours before and 24 hours after chemotherapy (18 participants) or eat regularly throughout treatment (18 participants).

Those in the fasting group could have as much water and herbal tea as they wanted, no more than two litres of vegetable juice, and small amounts of light vegetable broth. They could not take in more than 350 calories per day while fasting. Between chemotherapy sessions, they ate regularly.

Fasting was associated with lower insulin levels after three cycles of chemotherapy. In the fasting group, insulin levels went down 1.12µIU/ml, on average. In comparison, insulin levels went up by 9.76µIU/ml in the control group.

Fasting resulted in a better chemotherapy response. After the initial rounds of chemotherapy and before surgery, nearly three in five people who had fasted had a complete or nearly complete response (chemotherapy response score of three). In comparison, fewer than one in five in the control group had the same level of response.

Based on the data after about 18 months, researchers determined that fasting participants would stay cancer-free for more than three years, compared to about two years for the control group (median progression-free survival was 38 months vs 24 months, respectively).

Fasting was associated with changes in the body that indicate chemotherapy has a better chance of working, with the fasting group having fewer specialised immune cells that facilitate tumour progression.

Everyone in the fasting group completed their treatment. The most common adverse health effects in the study were low blood cell counts and haemoglobin levels, which is typical for chemotherapy. They occurred in similar numbers of participants in both groups.

“Fasting during chemotherapy is an area of growing research interest. This pilot randomised clinical trial showed that short-term fasting before and after each chemotherapy cycle led to a reduction in insulin levels after three neoadjuvant chemotherapy cycles and improved pathologic response and progression-free survival in patients with ovarian cancer.

“While this is a small study, the findings are encouraging, support earlier data, and highlight a promising area of cancer research, with larger clinical trials now needed to build on these results,” said Dr Eleonora Teplinsky, Head of Breast and Gynecologic Medical Oncology, Valley-Mount Sinai Comprehensive Cancer Care and an ASCO Expert in gynecologic cancers.

Researchers are continuing to study the data to understand how fasting changes the body. They hope to do a larger clinical trial to better understand how fasting or other diet changes affect cancer treatments.