You have to be careful in general whenever you are correlating two common features. If 80% of your deaths to a disease are among people who are overweight or obese, and 70% of your population is overweight or obese ... yes, there is a correlation. But it's a much weaker and less interesting correlation than if 20% of your population were overweight or obese, or if 97% of the people who died were obese or overweight.
