Obesity is a growing concern and is linked with several chronic disorders including diabetes and cardiovascular diseases. Is cancer one of the outcomes of the dangerous impacts of obesity? As reported by the international agency for research on cancer (IACR), 25% of cancer cases are associated with obesity or sedentary lifestyle.1 The World Cancer Research Fund calculated that 18% of cancers in the US are directly proportional to inadequate diet and being overweight. Based on substantial evidence suggesting that improvement in lifestyle and choices of food intake can help in cancer prevention and control, public health guidelines for at-risk individuals are developed worldwide.2

Although there is now increasing evidence suggesting the positive impact of exercise, diet and weight management in improving treatment outcomes and reducing adverse effects, there is however little guidance available on nutritional and lifestyle interventions in patients undergoing cancer treatment. This is very critical information for these patients wherein cancer treatment may have compromised their overall health and fitness levels, and predisposed them to other comorbidities. Based on systematic review of clinical data published in PubMed-indexed journals and the Cochrane Library from January 2000 to May 2021, together with public recommendations, recently ASCO published guidance on exercise, diet, and weight control in  patients undergoing cancer treatment.3

The ASCO guidance strongly recommends that cancer patients should practice aerobic and resistance training during their treatment; this is corraborated with several studies suggesting less fatigue, improved cardiorespiratory fitness, and fewer cases of anxiety and depression following exercise interventions in patients undergoing cancer treatment. Furthermore, improvement in cardiovascular function in these patients is directly proportional to the duration and frequency of exercise. Lifestyle interventions is also known to help the patients mitigate the severity and incidence of treatment-emergent adverse events. Resistance trainings may improve the upper- and lower body muscle strengths of patients undergoing chemotherapy as well as during pre-operative and postoperative stages. Aerobic and resistance exercise may help in restoring or improving the physical function and quality of life, which otherwise is known to be affected in various cancer treatments. Combined aerobic and resistance exercises may increase the body lean mass in these patients and help in weight management in these patients. Based on published evidence, moderate intensity exercises may help in improving sleep quality and cognitive function in patients undergoing chemotherapy. However, there is still insufficient evidence to derive at the dosing guidance for duration and/or intensity of exercises during cancer treatment. 

The ASCO guidance also suggested that oncologists can recommend preoperative exercises in lung cancer patients who are candidates for surgery to reduce hospitalizations and postoperative complications. The guidance also recommends that oncologists should regularly counsel patients and encourage them to exercise and implement a healthy lifestyle during their patient consultations. This is extremely important as most cancer patients are completely inactive or sub-optimally active during their treatment. Although referral to exercises and dietary interventions may depend on the patients’ comorbidities, treatment related side effects and physical activity, it is seen that regular patient-doctor engagement may encourage the patient to include regular physical exercise in disease management. Depending on the patient health, exercise may be carried out by the patient independently or under clinical supervision or using specialised rehabilitation programs; there is an unmet need to build all possible algorithms and decision tools that would enable the oncologist to recommend a safe and feasible option for the patient. 

Although there is insufficient evidence suggesting dietary interventions for improved clinical outcomes in patients undergoing cancer treatment, the ASCO guidance suggests that neutropenic diets (diets which exclude raw fruits and vegetables to decrease the microbial and bacterial exposure) may not be recommended in patients undergoing cancer treatment as this may limit some other vital nutrients and bioactive compounds essential for body function. Further studies are warranted to recommend for or against any intentional weight loss or avoiding weight gain dietary interventions during treatment that would improve the clinical outcomes and reduce the treatment toxicity in cancer patients. 

Lastly, the lack of guidance should not be interpretated as lack of value of dietary interventions during or after cancer treatment. It is just that the ASCO does not wish to endorse or prohibit any particular diet based on insufficient literature. Nevertheless, tt should be noted that weight management is an important issue given the high prevalence of obesity in cancer survivors and there is sufficient evidence suggesting ill effects of excess adiposity. Both exercise and diet are important in all individuals to lead a disease-free life.

References: 

1. https://www.iarc.who.int/featured-news/world-cancer-day-2021-physical-activity/

2. https://www.wcrf.org/cancer-trends/breast-cancer-statistics/

3. Ligibel J et al., Exercise, diet, and weight management during cancer treatment: ASCO guideline. J Clin Oncol. 2022;40:2491–2507.