Lifestyle cannot guarantee that breast cancer will be prevented or will not return. But there is substantial evidence that exercise, maintaining a healthy body composition, and good metabolic health can matter.
Regular physical activity is associated with a lower risk of developing breast cancer and, among women who have had breast cancer, with better overall health and in many studies better outcomes. Exercise also helps preserve muscle, strength, bone health, and quality of life during and after treatment.
Excess body fat—particularly after menopause—is associated with increased breast-cancer risk. Insulin resistance, high insulin levels, and diabetes have also been associated with poorer breast-cancer outcomes, although researchers are still working to understand how much these factors directly influence cancer.
Diet is more complicated. No single diet has been proven to prevent breast cancer or its recurrence. The strongest evidence favors an overall dietary pattern emphasizing minimally processed foods, adequate protein, vegetables and other whole foods, while limiting alcohol and highly processed foods.
For someone with breast cancer, lifestyle should therefore be viewed not as an alternative treatment, but as an opportunity to improve overall health and possibly create a metabolic environment less favorable to cancer.
Regular physical activity is one of the best-supported lifestyle measures for women with breast cancer. Women who are physically active have a lower average risk of developing breast cancer, and observational studies suggest that women who remain active after diagnosis may also have better outcomes.
Clinical trials provide particularly strong evidence that exercise can help during breast-cancer treatment.
The OptiTrain randomized trial studied 240 women receiving chemotherapy. Women participated in supervised exercise programs that included resistance training, aerobic exercise, and high-intensity interval training.
Women doing resistance and high-intensity interval training experienced less fatigue and fewer treatment-related symptoms and maintained greater muscle strength and cardiovascular fitness than women receiving usual care.
A later analysis produced a striking result: only 3% of women in the resistance/interval-training group were hospitalized during chemotherapy, compared with 15% receiving usual care. The exercise groups also had substantially less thrombocytopenia, a treatment-related reduction in blood platelets.
The benefits were strongest during treatment and shortly afterward. Five-year follow-up found that many of the differences between the original groups had diminished, suggesting that exercise needs to become an ongoing part of life rather than a temporary intervention during chemotherapy.
Both aerobic exercise and resistance training are valuable. Resistance training is particularly important for maintaining muscle and bone, which can be affected by aging, chemotherapy, and hormone therapy.
The practical message is encouraging: exercise can be considered part of supportive breast-cancer care, helping women maintain strength, fitness, and function while coping with treatment.
There is growing evidence that metabolic health may influence breast-cancer risk and outcomes. Excess body fat, particularly after menopause, is associated with increased breast-cancer risk, and researchers have become increasingly interested in the possible role of insulin and insulin resistance.
One particularly interesting study, Fasting Insulin and Outcome in Early-Stage Breast Cancer – Goodwin et al, followed 512 women with early-stage breast cancer who did not have known diabetes. Women with the highest fasting insulin levels had about twice the risk of the cancer recurring at a distant site and three times the risk of death compared with women who had the lowest insulin levels.
This was an observational study, so it cannot prove that high insulin caused the poorer outcomes. But the association was strong and remained substantial even after researchers took tumor characteristics and treatment into account.
Can insulin levels actually be changed? Clinical trials suggest they can.
In the WISER Survivor randomized trial, breast-cancer survivors who were overweight or obese were assigned to exercise, weight loss, a combination of exercise and weight loss, or a control group. Weight loss, particularly when combined with exercise, significantly reduced insulin and insulin resistance.
Another randomized study, the Yale Exercise and Survivorship Study, assigned 75 postmenopausal breast-cancer survivors to moderate aerobic exercise or usual care. Women in the exercise group showed favorable changes in insulin-related growth factors, as well as a decrease in insulin that did not reach statistical significance.
These studies do not yet prove that lowering insulin will prevent breast-cancer recurrence. But they provide an intriguing connection between breast cancer, insulin, body composition, and physical activity—and suggest that improving metabolic health is a worthwhile area of continuing research.
Diet studies in women with breast cancer have produced mixed results, and most of the large older trials did not specifically test low-carbohydrate or ketogenic diets.
Two important randomized trials illustrate the uncertainty.
The Women's Intervention Nutrition Study (WINS) enrolled 2,437 women with early-stage breast cancer. Women assigned to a low-fat dietary intervention reduced fat intake and also lost a modest amount of weight. The intervention group had fewer breast-cancer relapses, although it is difficult to know whether the benefit came from lower fat intake, weight loss, changes in insulin and metabolism, or some combination of these factors.
By contrast, the Women's Healthy Eating and Living (WHEL) Study enrolled more than 3,000 breast-cancer survivors and tested a diet very high in vegetables, fruit, and fiber and relatively low in fat. After more than seven years of follow-up, the diet did not reduce breast-cancer recurrence or mortality.
These results suggest that simply eating more fruits, vegetables, and fiber or reducing dietary fat may not by itself be enough to change breast-cancer outcomes.
More recent research has focused increasingly on insulin resistance, blood glucose, body composition, carbohydrate quality, and metabolic health. This has also led to clinical studies of low-carbohydrate and ketogenic diets, fasting, and time-restricted eating.
The evidence for these approaches in breast cancer is still developing, but the metabolic rationale is plausible and some early clinical studies are encouraging.
For someone interested in a low-carbohydrate approach, a reasonable goal is not simply to “eat less carbohydrate,” but to emphasize minimally processed foods, adequate protein, healthy fats, and avoidance of refined carbohydrates and added sugars, while maintaining muscle and overall nutritional adequacy.
Whether a grain-free diet provides any additional breast-cancer benefit has not been established, although eliminating refined grain products can substantially reduce the intake of rapidly absorbed carbohydrates and highly processed foods.
The evidence linking alcohol to the risk of developing breast cancer is strong. Risk rises as alcohol consumption increases, and even relatively small amounts appear to increase risk.
The National Cancer Institute estimates that, compared with nondrinkers, breast-cancer risk is about 4% higher in light drinkers, 23% higher in moderate drinkers, and 60% higher in heavy drinkers.
Alcohol may increase breast-cancer risk in several ways, including by raising estrogen levels and damaging DNA.
The evidence is less clear for women who have already been treated for breast cancer. Current studies have not established that alcohol increases the risk of recurrence, although the possibility remains and alcohol also increases the risk of several other cancers.
The American Cancer Society therefore says that avoiding alcohol is best. For women who choose to drink, it recommends no more than one drink per day.
For someone concerned about breast-cancer risk, reducing or eliminating alcohol is one of the more evidence-based lifestyle choices available.
Leigh Erin Connealy, MD, an integrative cancer physician, emphasizes treating the whole person as well as the cancer. She gives particular attention to metabolic health, including blood sugar and insulin, along with nutrition, exercise, sleep, stress, inflammation, hormones, and environmental exposures.
Connealy views metabolic dysfunction as especially important in the development and progression of cancer and often recommends reducing sugar and refined carbohydrates. Some of her views go beyond what has been established in conventional cancer research, but they provide another perspective on how metabolic and lifestyle factors might complement standard cancer treatment.
A Q&A with Dr. Connealy on Integrative Breast Cancer Treatment
Connealy discusses her approach to combining conventional breast-cancer treatment with nutrition, metabolic health, lifestyle, and whole-person care.
Would increasing my physical activity or strength training be particularly helpful during or after treatment?
Should I have my fasting glucose, fasting insulin, and HbA1c checked?
Do I have signs of insulin resistance or metabolic syndrome that would be worth addressing?
How important are body composition and maintaining muscle in my situation?
Are there reasons I should avoid a low-carbohydrate or ketogenic diet during my particular treatment?
Would fasting or time-restricted eating be safe with my treatment?
How might alcohol affect my breast-cancer risk and overall health?
Are there lifestyle or metabolic-health clinical trials that might be appropriate for me?
A randomized trial of 240 women receiving chemotherapy showing benefits from supervised aerobic and resistance exercise, including improvements in fatigue, symptoms, strength, and cardiovascular fitness.
A prospective study of 512 women with early-stage breast cancer. Higher fasting insulin was strongly associated with increased risk of distant recurrence and death.
A randomized trial showing that weight loss, particularly when combined with exercise, can reduce insulin and insulin resistance in breast-cancer survivors who are overweight or obese.
A randomized trial of 2,437 women with early-stage breast cancer. A low-fat dietary intervention, which also produced modest weight loss, was associated with fewer breast-cancer recurrences.
A randomized trial of 3,088 breast-cancer survivors. A diet very high in vegetables, fruit, and fiber and low in fat did not reduce breast-cancer recurrence or mortality after an average 7.3 years of follow-up.
A randomized clinical trial in women with locally advanced or metastatic breast cancer receiving chemotherapy. The ketogenic-diet group showed favorable changes in insulin and some measures of tumor response. The study was small, but the results support further investigation of low-carbohydrate metabolic approaches.
Explains the evidence linking alcohol consumption with breast cancer and other cancers. Even light alcohol consumption is associated with some increase in breast-cancer risk.