According to Fitness May Prevent Cancer Deaths Among Men, fit men and thin women are less likely to get cancer:
The study included 2,585 women and 2,890 men who were followed from the early- to mid-1970s to 1998. At the start of the study, volunteers performed a treadmill test to measure their heart health and had their body mass index, or BMI, measured. BMI is a measure of weight in relation to height used to gauge obesity.After taking into account factors that could influence health, Evenson’s team found that the fittest men were about half as likely to die from cancer as less fit men. Fitness levels did not have a significant effect on cancer deaths in women, however.
But a woman’s BMI at the start of the study was related to her chances of dying from cancer during the next 25 years, according to the report. Women with the highest BMI were almost 50% more likely to die from cancer than less obese women.