Can Cancer Be Prevented?
The most common conception, or rather misconception, about cancer seems to be that it strikes more or less randomly. Sure, the connection between smoking and cancer is well known, but aside from that most people believe that there’s nothing much they can do to prevent it.
But of course there are many things one can do, and perhaps one of the most important is exercise.
Obesity Increases Risk of Cancer through Higher Insulin
Consider that obesity is associated with a higher cancer risk, about 50% higher in men, 60% in women. One thing I like about this linked study is that it uses the body mass index (BMI) at the start of the study, not at time of diagnosis. Studies using BMI at time of death regularly underestimate the health risks of obesity, since sick people are likely to lose weight after they become ill.
Another study found that obese women, BMI>30, had a 2.5 fold increase in the risk of breast cancer, as compared to those with BMI
What’s the connection between obesity and cancer? It appears to be insulin. The overweight and obese typically have insulin resistance, and this leads to chronically elevated levels of insulin. Since insulin promotes growth, it may also promote the growth of tumors.
Exercise Leads to Lower Insulin Levels
Exercise leads to better insulin sensitivity and thus to chronically lower levels of insulin. Extremely short duration high intensity interval training substantially improves insulin action in young healthy males: in this study, young men did a grand total of 15 minutes of exercise. Yes, you read that right, 15 minutes over a period of two weeks, consisting of 4 to 6 cycle sessions of 30 seconds each, thrice weekly. In other words, so short a time that most people wouldn’t even consider it exercise, so conditioned as most people have been to think of exercise as something that must be carried out in longer, grueling sessions. The key of course lies in its intensity; I don’t know if you’ve ever cycled all-out, giving it all you’ve got, on a stationary cycle for 30 seconds, but I have, and it leaves you breathless. Now consider 4 to 6 of those separated by four minutes recovery between bouts. It’s a tough workout, even if the actual exercise is short. It’s not called high-intensity training for nothing.
The results in terms of insulin were that a glucose tolerance test showed that plasma insulin was nearly 40% lower than before training.
Therefore, since insulin levels and insulin resistance appear to be important to the up to 3-fold increase in cancer risk among the obese, lowering insulin through exercise could substantially lower cancer risk.
Indeed, among lean women who exercised at least 4 days a week, breast cancer risk was 70% lower; exercise alone, not taking into account BMI, lowered the risk by around 40%.
Weightlifting Decreases Insulin
Weightlifting also improves insulin sensitivity and decreases insulin levels, in this particular study insulin sensitivity increased nearly 50% in young, healthy men after only 6 weeks of 3-day a week, whole-body training. So weightlifting should be effective in cancer prevention, and I have little doubt that it is.
Abundant evidence also links the activation of AMPK to lower cancer risk, and exercise, along with fasting, resveratrol, curcumin, and some other things, activates AMPK. Metformin, a diabetes drug which activates AMPK, also reduces cancer risk, showing the importance of AMPK in this regard.
Both epidemiological and laboratory evidence points to the large effects of exercise in reducing cancer risk.