Obesity is a well-known risk factor for cancer, but does muscularity have any protective effect? Researchers from the Cooper Institute, which is the home of “aerobics”, wanted to know, and took a look at participants there. In this study, they looked at 8,677 men, age 20 to 82, whom they followed over a period of over two decades. Specifically, they wanted to understand “the associations between muscular strength, markers of overall and central adiposity, and cancer mortality in men.” They found that muscular strength is associated with lower cancer mortality. Far lower. Muscular Strength and Adiposity as Predictors of Adulthood Cancer Mortality in Men.
In sum, they found that the highest third of the group in muscle strength had about 40% lower cancer mortality than the lowest third in muscle strength. They also found, as expected, that higher body mass index, as well as higher percent body fat, were both associated with much higher rates of death through cancer; the obese had a cancer death rate almost double that of men with a normal BMI.
But here’s the real kicker: after adjusting for muscular strength, the associations of cancer with body mass index and body fat disappeared.
The associations of BMI, percent body fat, or waist circumference with cancer mortality did not persist after further adjusting for muscular strength (all P ≥ 0.1).
Higher levels of muscular strength are associated with lower cancer mortality risk in men, independent of clinically established measures of overall and central adiposity, and other potential confounders.
Amazing. “The associations of BMI, percent body fat, or waist circumference with cancer mortality did not persist after further adjusting for muscular strength (all P ≥ 0.1).” Muscular strength trumped all the other mentioned markers when it came to cancer mortality. The cancer risk at the highest tertile of strength was 40% less than the lowest.
This is of course association; it was not a randomized clinical trial. But the association of muscular strength with lower cancer mortality is striking, and especially the fact that it is a better marker than body fat or BMI.
This certainly suggests that regular resistance training is a good way to beat cancer. The authors believe that muscular strength is a proxy for regular exercise: “The apparent protective effect of muscular strength against cancer is likely to be due to a consequence of regular physical exercise, specifically resistance exercise.” Yet, it seems specifically resistance training that gives the benefits, since cardio does little to improve muscular strength.
One way in which resistance training likely decreases cancer risk is through improved insulin sensitivity. And the way that this type of training is superior to aerobic exercise is that collectively, the skeletal muscles make up a large portion of body weight; therefore insulin sensitivity is improved more than with cardio.
Even in those who have already had cancer, weightlifting is associated with far less cancer mortality.
Moral of the story: lift weights, beat cancer.