Not that I'm disagreeing with the limitations of observational studies, but it's not quite that simple. Cancer Research UK describes being overweight or obese a

Not that I'm disagreeing with the limitations of observational studies, but it's not quite that simple. Cancer Research UK describes being overweight or obese as the second biggest preventable cause of cancer (after smoking): https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/obesity-weight-and-cancer/does-obesity-cause-cancer https://www.cancerresearchuk.org/about-cancer/causes-of-canc... In particular, there appears to be a causal link between being fat and an increased risk of some cancers via several identified mechanisms, though of course this whole area is a subject of ongoing research. Given the well-understood links between a healthy diet, getting enough exercise, and maintaining a healthy body composition, it's important to pay attention to both diet and exercise in order to minimise cancer risk, even taking into account the other effects.