Research increasingly links metabolic health with cancer risk and outcomes. Obesity, insulin resistance, high blood sugar, and related metabolic problems have been associated with worse outcomes in several cancers and with a greater risk of aggressive or fatal prostate cancer.
Doctors and researchers such as Robert Lustig and Jason Fung emphasize the role of insulin, diet, obesity, and metabolic dysfunction in creating an environment that may encourage cancer growth. Both advocate reducing added sugar and refined carbohydrates and eating primarily whole, minimally processed foods. Fung also emphasizes fasting as a way of lowering insulin and improving metabolic health.
This does not mean that sugar causes prostate cancer or that eliminating carbohydrates can cure it. But maintaining good weight, insulin sensitivity, muscle mass, and overall metabolic health may be particularly worthwhile for men with prostate cancer—especially those receiving hormone therapy, which itself can adversely affect metabolic health.
Diet and lifestyle should therefore be viewed as important parts of overall health during prostate cancer, while their role as direct cancer treatments continues to be studied.
There is no single diet proven to treat prostate cancer. But a dietary pattern that supports good metabolic health is a reasonable goal.
Useful principles include:
Eat primarily whole, minimally processed foods
Minimize added sugar and refined carbohydrates
Limit ultra-processed foods
Include adequate protein to help maintain muscle, particularly during hormone therapy
Eat vegetables and other fiber-rich foods
Avoid gaining excess body fat and, when appropriate, work toward a healthy weight
For people who are insulin resistant, reducing carbohydrates may help improve blood sugar, insulin levels, weight, and other metabolic markers.
A therapeutic ketogenic diet is a different question. It is being studied as a possible metabolic cancer therapy, but it has not been established as a treatment for prostate cancer.
Jason Fung has written extensively about fasting as a way to lower insulin, improve insulin sensitivity, and reduce excess body fat. These effects may improve metabolic health, which is valuable whether or not someone has cancer.
Fasting also affects cellular processes such as autophagy, the system cells use to recycle damaged or unnecessary components. This has led researchers to investigate whether fasting or fasting-mimicking diets might influence cancer development or improve responses to cancer treatment.
The evidence for fasting as a cancer treatment in humans remains limited. It has not been established as a treatment for prostate cancer, and prolonged fasting can be particularly concerning for people who are already losing weight or muscle during cancer treatment.
For someone with prostate cancer, fasting is best considered primarily as a metabolic-health strategy, with more intensive fasting during treatment discussed with the medical team.
Exercise may be one of the most useful lifestyle strategies for men with prostate cancer. It improves insulin sensitivity, cardiovascular fitness, strength, and overall metabolic health.
It becomes particularly important for men receiving androgen-deprivation therapy (ADT). Lower testosterone can lead to loss of muscle and bone, increased body fat, fatigue, and worsening metabolic health.
Resistance training helps preserve muscle and strength, while aerobic exercise supports cardiovascular fitness and metabolic health. Combining the two is particularly useful.
Exercise should not be viewed simply as an additional cancer treatment. It is an important way to maintain strength, independence, metabolic health, and quality of life during and after prostate cancer treatment.
Insulin is essential for regulating blood sugar, but it also acts as a growth signal. Chronically elevated insulin is one feature of insulin resistance, which commonly accompanies obesity and metabolic syndrome.
Research has found associations between obesity and metabolic dysfunction and more aggressive or fatal prostate cancer. The relationship is complex, however, and does not mean that high insulin alone causes prostate cancer.
Robert Lustig emphasizes how diets high in added sugar and ultra-processed foods can contribute to insulin resistance, fatty liver, and metabolic disease. Jason Fung similarly focuses on reducing chronically elevated insulin through diet, weight management, and periods without eating.
These ideas suggest a practical goal regardless of their precise role in cancer: maintaining good insulin sensitivity and metabolic health is beneficial for overall health and may be especially important for men being treated for prostate cancer.
Dr. Fung’s book examining cancer through genetics, evolution, metabolism, and the body's internal environment.
A discussion of sugar, insulin resistance, metabolic health, and chronic disease.
Dr. Fung discusses the changing understanding of what causes cancer and explores how obesity, insulin resistance, diet, and other metabolic factors may influence cancer development and growth.
A discussion of exercise and its role in prostate cancer care.