A new study based in Italy found that fasting before and after chemotherapy sessions, when compared with regular eating, can help reduce insulin levels and may improve treatment response for people with high-grade serous ovarian cancer (HGSOC).

The research will be presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, taking place May 29 to June 2 in Chicago. 

A new study based in Italy found that fasting before and after chemotherapy sessions, when compared with regular eating, can help reduce insulin levels and may improve treatment response for people with high-grade serous ovarian cancer (HGSOC).

The research will be presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, taking place May 29 to June 2 in Chicago. 

“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 Claudia Marchetti, MD, of the Fondazione Policlinico Universitario Agostino Gemelli in Rome, Italy.

This 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 3 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 2 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.

Key Findings

• Fasting was associated with lower insulin levels after 3 cycles of chemotherapy. In the fasting group, insulin levels went down 1.12 micro-International units per millilitre of blood (µIU/ml), on average. In comparison, insulin levels went up by 9.76 µIU/ml in the control group.
• Fasting resulted in a better chemotherapy response. After the initial rounds of chemotherapy and before surgery, nearly 3 in 5 people who had fasted had a complete or nearly complete response (chemotherapy response score of 3), indicating that the tumour responded very well to treatment. In comparison, fewer than 1 in 5 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 3 years, compared to about 2 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 3 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 Eleonora Teplinsky, MD, Head of Breast and Gynecologic Medical Oncology at 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 want to see how those changes relate to the immune system and to how well cancer therapies work.

They hope to do a larger clinical trial to better understand how fasting or other diet changes affect cancer treatments.

This was a nonprofit study that was conducted without commercial funding.  

Source: ASCO