What Should Nutrition and Exercise Be Like During Cancer Treatment?

Cancer affects people's lives in various ways, both as a disease and through the adverse effects of its treatment. Nutritional disturbances and reduced physical activity are among the main negative effects. Many scientific studies have examined diet and exercise in people with cancer. This article summarizes findings from prominent studies in this field.

Nutrition During Cancer Treatment: Does Any Particular Diet Stand Out?

There is insufficient evidence to recommend for or against dietary interventions such as ketogenic diets, low-carbohydrate diets, low-fat diets, functional foods or intermittent fasting to improve quality of life, treatment side effects or cancer outcomes during treatment.

Systematic reviews have evaluated a wide range of dietary interventions during cancer treatment, including changes in the timing of food intake, such as intermittent fasting; dietary patterns; macronutrient composition, such as low-fat or low-carbohydrate diets; and the amount consumed.

Switching to a Special Diet During Treatment Does Not Affect Disease Outcomes

Very little is known about the effects of dietary changes during treatment on cancer outcomes; it would not be wrong to say there is almost no information. Most studies are small, often involving fewer than 100 patients with different cancer types and stages. Their findings have generally failed to demonstrate consistent effects of dietary changes during treatment on patient-reported or other outcomes in people with cancer.

Patients With Weakened Immunity During Cancer Treatment: Neutropenic Diets

Neutropenia is a reduction in neutrophils, the most common type of white blood cell in the immune system. A person's neutrophil count is an important indicator of infection risk. Cancer treatments, particularly some chemotherapies, can cause neutropenia.

People with cancer are thought to need greater care with their diet when they become neutropenic. However, there is no standard definition of a neutropenic diet. Such diets, particularly those excluding raw fruits and vegetables, are frequently recommended to prevent infection during active cancer treatment. Current data, however, suggest that the harms of neutropenic diets outweigh their benefits. 

In an analysis including studies of children and adults, infection was recorded in 53.7% of patients assigned to a neutropenic diet and 50% of those eating a normal diet; avoiding raw fruits and vegetables therefore did not reduce infection risk. Another study enrolled 153 patients receiving induction chemotherapy for acute myeloid leukemia (age range 17-88). Patients were divided into 2 groups receiving either a diet without raw fruits or vegetables (cooked diet) or one containing fresh fruits and vegetables (raw diet). Serious infections occurred in 29% of patients on the cooked diet and 35% on the raw diet; the difference was not significant. There was no significant survival difference between the two diets.

Intentional Weight Loss for Cancer Treatment

There is insufficient evidence to recommend for or against intentional weight-loss interventions during active treatment to improve treatment side effects or cancer outcomes. Evidence on the risks and benefits of weight loss during treatment remains uncertain.

Limited available evidence suggests that intentional weight loss is possible during cancer treatment, particularly in people treated for breast and prostate cancer. However, there is currently little evidence that it provides substantial benefits during active treatment.

The idea of losing weight during cancer treatment arises from the claim that cancer cells use sugar molecules for nutrition and cannot grow and multiply without sugar intake (see our article Does sugar feed cancer? ). However, scientific studies have shown that cancer cells can also use nutrients other than sugar and that eliminating sugar is not effective in shrinking tumors. Nevertheless, given the substantial observational data suggesting an association between excess body fat or obesity and increased cancer risk, more research is needed in this area.

Nutrition During Cancer Treatment: Conclusions

There are currently very few data to support particular dietary changes or foods as part of cancer treatment.

Neutropenic diets, generally defined as diets aiming to reduce bacterial exposure by restricting raw fruits and vegetables, have long been recommended to prevent infection in patients with hematologic malignancies, particularly those who have undergone bone marrow transplantation. Data do not support their use to reduce infection risk in this group.

Given that these diets are also less palatable and may restrict important nutrients and bioactive compounds, the American Society of Clinical Oncology (ASCO) Expert Panel emphasized that current data show no difference in infection risk with a neutropenic diet and that harms generally outweigh potential benefits.

In conclusion, one of the healthiest dietary patterns that can be recommended both during and after cancer treatment is the Mediterranean diet. We should regard plant-rich eating, as in this diet, as an important part of healthy living.

Exercise During Cancer Treatment

Aerobic and resistance exercise should be recommended during active treatment to reduce the side effects of cancer treatment.

What Is Aerobic Exercise?

Aerobic exercise involves activities performed continuously at a particular pace for a period of time, requiring substantial oxygen consumption. These body-strengthening activities can be thought of as low-intensity exercise that can be sustained for a long time.

The final results of reviews including many independent studies assessing the effects of exercise on maximal or peak oxygen consumption were consistent, reporting moderate-to-large benefits from exercise. Neoadjuvant (tumor-shrinking treatment before the main treatment) or adjuvant treatment (given afterward to reduce recurrence risk) was received by patients in studies included in a 2019 analysis evaluating resistance or aerobic exercise. The analysis found that exercise moderately improved maximal oxygen consumption (VO2 max).

Another analysis reviewing studies in breast cancer treated with adjuvant chemotherapy and/or radiotherapy, colorectal cancer treated with chemotherapy, lung cancer treated with chemotherapy, prostate cancer treated with radiotherapy, and hematologic cancers also reported a moderate reduction in fatigue with exercise during cancer treatment.

Recommended Exercise Programs During Cancer Treatment

Most reviews pooled data from delivery models and programs for various forms of exercise, allowing the effects of aerobic and resistance exercise to be distinguished or the duration, schedule or intensity of exercise to be determined.

The analyses showed significant reductions in fatigue following resistance and aerobic exercise interventions. Finally, a review of studies examining exercise and strength in men with prostate cancer suggested a significant association between resistance exercise and changes in upper-body strength.

What Are the Benefits of Regular Exercise During Cancer Treatment?

Having a regular exercise program during cancer treatment affects several factors besides fatigue. Areas that improve with exercise include:

• Muscle strength
• Physical function
• Depression and anxiety
• Body composition
• Sleep
• Chemotherapy side effects
• Surgical side effects

Muscle Strength

Analyses of studies evaluating aerobic and/or resistance exercise and muscle strength in men receiving prostate cancer treatment show significant, consistent improvements in upper- and lower-body strength. Evidence in other cancers is less consistent, although improved upper- and lower-body strength has been reported in patients with breast cancer.

Physical Function

Analyses evaluating aerobic and/or resistance exercise interventions during cancer treatment show small but statistically significant improvements in self-reported and objectively measured physical function.

Depression and Anxiety

Analyses reviewing many studies of depression and anxiety suggest that, in patients with breast cancer, exercise during treatment may reduce both depression and anxiety. Fewer studies addressed other cancers, and meta-analyses in patients with colorectal cancer, hematologic malignancies and lung cancer found no significant differences.

Body Composition

Analyses of studies in patients receiving prostate cancer treatment show that resistance exercise moderately reduces body fat percentage.

Sleep

An analysis reviewing two breast cancer studies reported a moderate reduction in sleep disturbance with exercise interventions during treatment. A systematic review of 301 patients with breast cancer suggested that higher-dose aerobic exercise during chemotherapy might improve sleep quality.

Chemotherapy

Relatively little information is available about the effects of exercise interventions during cancer treatment on chemotherapy completion or dose intensity. The limited evidence comes from two breast cancer studies, which reported benefits.

Surgery

Many analyses have evaluated preoperative exercise and postoperative complications and other outcomes in patients undergoing surgery for lung, gastrointestinal or genitourinary cancers. Two 2019 analyses reviewing studies focused particularly on non-small cell lung cancer reported that preoperative exercise reduced postoperative hospital stays.

Oncology specialists may recommend preoperative exercise to patients undergoing lung cancer surgery to reduce hospital stays and postoperative complications.

Exercise in People Living With Advanced Cancer

The literature assessing the safety and potential benefits of exercise in patients with advanced cancer is relatively limited.

A 2021 systematic review assessed the safety and potential benefits of exercise interventions in patients with bone metastases. Groups containing a mixture of patients with and without bone metastases were identified. Some individual studies reported benefits in outcomes such as physical function. Serious side effects were rare even in patients with bone metastases.

Another analysis reviewing studies with small numbers of patients with advanced lung cancer reported an improvement in disease-specific health-related outcomes with exercise.

Exercise During Cancer Treatment: Conclusions

Aerobic and resistance exercise during cancer treatment has numerous well-documented benefits for patients receiving curative-intent treatment. It also reduces other treatment side effects, including fatigue and mood disturbances, and helps maintain strength, particularly in men receiving prostate cancer treatment. Including exercise may improve treatment tolerability, fitness and functional status in patients undergoing treatment.

Although the literature on exercise during active cancer treatment has examined different forms of exercise with varying programs, intensities and delivery methods, results consistently show reduced symptoms such as fatigue. Studies have also shown fewer treatment side effects in patients participating in exercise interventions during cancer treatment.

Although data are more limited, exercise interventions also appear beneficial before lung cancer surgery. Preoperative exercise may benefit patients with other cancers, but evidence is currently weaker than for lung cancer. Given these benefits, various guidelines recommend exercise for patients with cancer and survivors.

In conclusion, based on this evidence, exercise should be included as a standard part of oncology treatment.

Health Inequities and Their Effects on Nutrition and Exercise

Although ASCO clinical practice guidelines provide expert recommendations on best practices in disease management to deliver the highest standard of cancer care, many patients have limited access to medical care. Factors such as race and ethnicity, age, socioeconomic status, sexual orientation and gender identity, geographical location and access to insurance are known to affect diet and exercise behaviors as well as cancer treatment outcomes.

Factors related to cancer disparities also affect patients' ability to exercise adequately, follow a plant-based diet with fewer refined grains, sugars, and red and processed meats, and succeed in these efforts.

Sociodemographic factors such as age, race and education further widen these differences, emphasizing the need for social workers and adequate social support.

Summary

A recent ASCO study showed that regular exercise, maintaining a healthy weight and eating a high-quality diet have long-established value in reducing the risk of cardiovascular disease, metabolic disorders and other chronic illnesses.

Improving lifestyle behaviors earlier in cancer care may provide longer-term benefits not reflected in the current literature.

However, reviewing the published literature reveals a profound gap in high-quality research on optimal diet, weight-management and exercise strategies aimed at reducing both acute and long-term side effects.

Future research should include more diverse patient samples. Studies are needed in cancers other than the most frequently studied breast, prostate, lung and colorectal cancers, in patients receiving immunotherapy, and in those with metastatic (stage 4) disease. Studies should test interventions in medically vulnerable people, paying attention to eligibility criteria or allowing results to be stratified.

In summary, a commitment to studies providing high-quality evidence is essential. Many studies reviewed were of low quality, contributing to weak recommendations. Future research should be conducted rigorously with adequate sample sizes and methods that reduce bias and confounding and increase the certainty of evidence, strengthening research quality and future guidelines.

Finally, remember that some patients may be unaware of how exercise during treatment affects outcomes, while others may adopt exercise and dietary changes unsupported by evidence. Doctors should explain the importance of exercise during cancer treatment and make appropriate referrals that encourage healthy lifestyle behaviors. In a recent ASCO survey, 84% of oncologists acknowledged the benefits of diet, exercise and weight management but felt that another team member should deliver the interventions.