Ovarian cancer response to chemotherapy may improve with fasting | ASCO 2026

Patients with high-grade serous ovarian cancer (HGSOC) who fasted before and after three chemotherapy appointments saw improved treatment outcomes and lower insulin levels than patients who did not fast, according to the results of an Italian study that will be presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting.

The study was led by Claudia Marchetti, M.D., of the Fondazione Policlinico Universitario Agostino Gemelli in Rome, Italy. It enrolled 36 patients in treatment for stage III or IV HGSOC, who were randomized 1:1 to fast or eat regularly.

Marchetti and her team found that insulin levels went down 1.12 micro-international units per milliliter of blood (µIU/ml), on average, in women who fasted. In women who did not fast, insulin levels rose by 9.76 µIU/ml.

Fasting also resulted in a better chemotherapy response. In the fasting group, nearly 3 in 5 patients had a complete or nearly complete chemotherapy response of 3. In contrast, less than 1 in 5 members in the non-fasting group had an equal response.

“Our conclusion is that shorter fasting induces favorable metabolic shifts,” Marchetti said during an ASCO press briefing. “It is feasible and well tolerated; it helps achieve better treatment response and also longer progression-free survival.”

All participants received three rounds of carboplatin and paclitaxel chemotherapy before tumors were removed. Specifically, half of the patients were instructed to fast for 36 hours before their chemotherapy treatment and 24 hours after. The other half of the patients were instructed to eat regularly throughout their treatment.

Specific fasting rules included consuming no more than 350 calories a day. However, they were allowed to drink as much herbal tea or water as they wanted, but no more than 2 liters of vegetable juice.

Worldwide, ovarian cancer affects more than 324,000 women.

In the United States, HGSOC is the most common form of ovarian cancer and the most severe, accounting for 70% to 80% of all ovarian cancer deaths annually. It often goes unnoticed because symptoms, such as bloating and abdominal pain can be mistaken for gastrointestinal issues.

“Ovarian cancer is frequently diagnosed at an advanced stage, and nearly half of patients are not suitable for primary surgery at diagnosis,” Marchetti said. “Therefore, half of them require neoadjuvant chemotherapy, followed by interval developing surgery.”

Prognosis also improved in the fasting group, with an estimated cancer-free survival rate of 3 years, compared with approximately 2 years for those who did not fast.

“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,” Marchetti said in a separate press release.

Marchetti and her team will continue to study how fasting can change insulin levels in the body and other types of cancer.

“We also observed preliminary signals of immune response, and now we are currently undergoing further analysis with regards to lymphocytes,” Marchetti continued. “We are planning a larger randomized multicenter trial to further validate our finding.”