Exactly how obesity promotes tumor growth is unknown, but people with more fatty tissue do have higher levels of insulin and estrogen, which encourage cell division. Weight loss causes a drop in hormone levels, so it’s extremely likely that it reduces cancer risk. To prove it, though, scientists would need to conduct another study using people who had successfully lost a lot of weight. The sad reason they haven’t? “There aren’t enough subjects,” says lead author Jeanne Calle. For now, the ACS says the obese (technically, anyone with a body-mass index of more than 30) don’t need more cancer screening. But it does suggest that they slim down. As if there weren’t already enough reasons to do that.
