Diet, Exercise & Metabolic Health
Lifestyle cannot guarantee that breast cancer will be prevented or will not return. But there is substantial evidence that exercise, healthy body composition, and metabolic health matter.
Regular physical activity is associated with a lower risk of developing breast cancer and helps women maintain 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, elevated insulin, and diabetes have also been associated with poorer outcomes, although whether improving these factors reduces recurrence remains uncertain.
No single diet has been proven to prevent breast cancer or recurrence. The strongest evidence favors minimally processed foods, adequate protein, vegetables and other whole foods, and limiting alcohol and highly processed foods.
Lifestyle should complement—not replace—appropriate cancer treatment.
Exercise and Breast Cancer
Exercise is one of the best-supported lifestyle measures during and after breast-cancer treatment.
The OptiTrain randomized trial studied 240 women receiving chemotherapy. Supervised exercise combining resistance and aerobic or interval training reduced fatigue and treatment-related symptoms and helped maintain muscle strength and cardiovascular fitness.
Both aerobic exercise and resistance training are valuable. Resistance training is particularly important for preserving muscle and bone, which can be affected by aging, chemotherapy, and hormone therapy.
The practical message is straightforward: exercise can be an important part of supportive breast-cancer care.
Body Weight, Insulin & Metabolic Health
Excess body fat after menopause is associated with increased breast-cancer risk, and researchers are increasingly interested in insulin and insulin resistance.
One study followed 512 women with early-stage breast cancer without known diabetes. Women with the highest fasting insulin had about twice the risk of distant recurrence and three times the risk of death compared with those with the lowest levels.
This was an observational study and does not prove that insulin caused the poorer outcomes.
Clinical trials do show that metabolic health can be improved. In the WISER Survivor trial, weight loss—particularly combined with exercise—reduced insulin and insulin resistance in breast-cancer survivors who were overweight or obese.
Whether lowering insulin actually reduces breast-cancer recurrence remains uncertain, but the connection between body composition, insulin, exercise, and breast cancer deserves further study.
What Does the Research Say About Diet?
Diet studies have produced mixed results, and no particular diet has been established as the best diet for preventing breast-cancer recurrence.
In the WINS trial, women assigned to a low-fat diet also lost modest weight and had fewer breast-cancer recurrences. It is unclear whether this resulted from lower fat intake, weight loss, metabolic changes, or a combination.
By contrast, the large WHEL trial tested a diet very high in vegetables, fruit, and fiber and relatively low in fat. It did not reduce recurrence or mortality.
Researchers are now studying low-carbohydrate and ketogenic diets, fasting, and time-restricted eating, partly because of their effects on glucose and insulin. Evidence in breast cancer remains limited, although some early studies are encouraging.
There is currently no evidence that a grain-free diet itself provides additional protection against breast cancer.
Alcohol and Breast Cancer
The evidence linking alcohol with developing breast cancer is strong. Risk increases with consumption, and even relatively small amounts are associated with some increase in risk.
Alcohol may contribute through several mechanisms, including raising estrogen levels and damaging DNA.
Evidence about alcohol and breast-cancer recurrence is less certain. But because alcohol also increases the risk of several other cancers, reducing or avoiding it is one of the more evidence-based lifestyle choices available.
An Integrative Perspective
Leigh Erin Connealy, MD, an integrative cancer physician, emphasizes nutrition, metabolic health, exercise, sleep, stress, and other lifestyle factors alongside conventional cancer treatment.
She places particular emphasis on blood sugar, insulin, and reducing sugar and refined carbohydrates. Some of her recommendations go beyond what has been established in clinical cancer research, but her approach illustrates the growing interest in metabolic health as a complement to standard treatment.
Connealy discusses combining conventional breast-cancer treatment with nutrition, metabolic health, and lifestyle.
Questions to Ask Your Doctor
What kinds of exercise would be most useful during or after treatment?
How important are maintaining muscle and a healthy body composition for me?
Should my glucose, HbA1c, or other metabolic markers be checked?
Would a lower-carbohydrate diet be appropriate during my treatment?
Would fasting or time-restricted eating be safe for me?
How should I think about alcohol?
High-Dose Intravenous Vitamin C
Researchers are investigating whether high-dose intravenous vitamin C can improve cancer treatment.
Small studies involving breast cancer patients have reported improvements in symptoms such as fatigue and nausea, but there is not yet convincing evidence that intravenous vitamin C improves survival or prevents recurrence.
Learn More
A randomized trial showing benefits from supervised aerobic and resistance exercise during chemotherapy.
A prospective study finding a strong association between higher fasting insulin and poorer breast-cancer outcomes.
A randomized trial showing that weight loss, particularly combined with exercise, can reduce insulin and insulin resistance.
A randomized trial in which a low-fat dietary intervention accompanied by modest weight loss was associated with fewer breast-cancer recurrences.
A large randomized trial in which a diet high in vegetables, fruit, and fiber and low in fat did not reduce breast-cancer recurrence or mortality.
A small randomized trial suggesting that a ketogenic diet may improve insulin and some measures of tumor response during chemotherapy. Further research is needed.
An overview of the evidence linking alcohol with breast cancer and other cancers.
Video
Practical guidance on aerobic exercise, strength training, lymphedema, and safely remaining active during and after treatment.