Researchers looked at 21 studies involving 1,384 cancer patients to see if exercise, diet changes, or both could help chemotherapy work more effectively. They found that certain diets—especially ketogenic (very low-carb) and fasting-mimicking diets—showed promise in helping tumors shrink and improving survival in some cases. Exercise alone showed fewer benefits for tumor response. While these findings are encouraging, scientists say we need more high-quality studies to be sure these lifestyle changes can truly boost cancer treatment success.

The Quick Take

  • What they studied: Whether exercise, special diets, or a combination of both could help chemotherapy drugs work better at fighting cancer and improving patient survival
  • Who participated: 21 different research studies involving 1,384 cancer patients total. Most studies focused on breast cancer patients, and researchers looked at what happened when patients exercised, changed their diet, or did both while receiving chemotherapy
  • Key finding: Certain diets—particularly ketogenic diets (very low in carbs) and fasting-mimicking diets (eating very little for short periods)—showed promise in helping tumors respond better to chemotherapy and improving survival in some studies. Exercise alone showed mixed results with limited evidence of helping tumors shrink
  • What it means for you: If you or a loved one is undergoing chemotherapy, these findings suggest that diet changes might be worth discussing with your cancer care team, but exercise and diet should never replace standard cancer treatment. More research is needed before doctors can confidently recommend these as standard additions to chemotherapy

The Research Details

This was a systematic review, which means researchers searched five major medical databases (PubMed, Medline, CINAHL, Embase, and Web of Science) to find all published studies about exercise, diet, or both in cancer patients receiving chemotherapy. They followed strict guidelines called PRISMA to make sure they did this search fairly and completely.

The researchers then carefully examined each study they found, looking at how well it was designed and whether the results were reliable. They used special tools to check for bias—meaning they looked for things that might have made the results unfair or inaccurate. They organized the studies by type: 13 looked at exercise, 7 looked at diet changes, and 1 looked at combining both exercise and diet.

This approach is like gathering all the puzzle pieces from different research teams to see what the bigger picture shows. It’s stronger than looking at just one study because it combines information from many different groups of patients and researchers.

A systematic review is important because individual studies can sometimes give confusing or contradictory results. By looking at all the available research together, scientists can see patterns and get a clearer picture of what actually works. This helps doctors and patients make better decisions about whether to try these lifestyle changes alongside their cancer treatment

The researchers used established tools to check the quality of each study they included. However, they found that the studies varied quite a bit in how well they were designed—some were very rigorous while others had weaknesses. The fact that results were inconsistent across studies (some showed benefits while others didn’t) means we should be cautious about drawing firm conclusions. The researchers themselves noted that more high-quality studies are needed before we can be confident in these findings

What the Results Show

Exercise interventions were studied in 13 research projects, but only 9 of these had a control group (a comparison group that didn’t exercise) to make fair comparisons. Of these 9 controlled studies, only 2 reported that exercise helped tumors respond better to chemotherapy. Importantly, none of the exercise studies showed that exercise improved how long patients survived.

Dietary interventions were studied in 7 research projects, and all of them tested either ketogenic diets or fasting-mimicking diets. Only 3 of these studies had control groups for fair comparison, and they all focused on breast cancer patients. The good news: 3 studies showed that these special diets led to better tumor response and improved survival outcomes.

Only one study looked at combining exercise and diet together. This single study reported that patients who did both exercise and diet had better pathological complete response rates—meaning the tumors showed more signs of being destroyed by the chemotherapy.

Overall, the dietary approaches, especially the ketogenic and fasting-mimicking diets, showed more promise than exercise alone for helping chemotherapy work better.

The review found that exercise and dietary interventions were generally safe and didn’t cause serious problems for cancer patients. Patients also reported feeling better emotionally and physically when they participated in these interventions. However, these quality-of-life improvements didn’t always translate into better tumor shrinkage or longer survival, which is what doctors most want to see

Previous research has shown that exercise and diet changes help cancer patients feel better and maintain their strength during treatment. This review builds on that by asking a harder question: do these changes actually help the cancer treatment itself work better? The findings suggest that diet changes might do more than just help patients feel better—they might actually help fight the cancer. However, this is a newer area of research with limited evidence so far

The researchers found several important limitations: First, there weren’t many high-quality studies to review—only 21 total, and many weren’t designed as rigorously as they could have been. Second, the studies looked at different types of cancer, different diets, and different exercise programs, making it hard to compare them fairly. Third, most studies were small with few patients. Fourth, the results were inconsistent—some studies showed benefits while others didn’t. Finally, only one study looked at combining exercise and diet, so we don’t know much about that approach yet

The Bottom Line

Based on current evidence: (1) Ketogenic and fasting-mimicking diets show the most promise and may be worth discussing with your cancer care team—moderate confidence level; (2) Exercise appears safe and helps with quality of life but shows limited evidence for improving tumor response—low to moderate confidence; (3) The combination of exercise and diet needs more research—low confidence. Always discuss any diet changes or exercise programs with your oncology team before starting, as some approaches might interfere with certain chemotherapy drugs

Cancer patients currently undergoing chemotherapy should care about this research, especially those with breast cancer (since most studies focused on this type). Patients should NOT use these interventions as replacements for standard chemotherapy. Family members and caregivers should also understand that while these approaches show promise, they’re not yet proven enough to be standard recommendations. Doctors and oncology teams should consider discussing these options with appropriate patients while emphasizing that more research is needed

If someone were to try these interventions, they wouldn’t see results immediately. Tumor response typically takes weeks to months to measure, and survival benefits take even longer to assess. Any changes should be monitored through regular imaging and blood tests with your cancer care team, not through how you feel

Want to Apply This Research?

  • Track weekly exercise minutes (if approved by your care team) and daily diet adherence to either ketogenic or fasting-mimicking diet protocols. Record any side effects, energy levels, and appetite changes. Sync this data with oncology appointments to discuss patterns
  • If your doctor approves, start with one small change: either a 15-minute daily walk or one day per week of modified fasting (under medical supervision). Use the app to set reminders and track consistency. Gradually increase as tolerated and approved by your care team
  • Create a monthly check-in system within the app to review: (1) consistency with exercise or diet changes, (2) any side effects or concerns, (3) upcoming oncology appointments where you can discuss results, (4) energy and mood changes. Share summaries with your care team quarterly

This research summary is for educational purposes only and should not replace professional medical advice. Cancer treatment decisions must be made in consultation with your oncology team. Exercise and dietary changes should only be undertaken with explicit approval from your cancer care doctors, as some approaches may interfere with chemotherapy effectiveness or cause harmful interactions. Always inform your medical team about any lifestyle changes you’re considering. This review shows promising early findings but emphasizes that more research is needed before these interventions can be recommended as standard practice