Link In summary, there's some (non-conclusive, but strong) evidence to suggest that it's specifically sugar (cane sugar, high fructose corn syrup, no difference), and not just overconsumption of calories, that causes diabetes and in turn leads to obesity. The pathway looks like this:
- Large amounts of glucose and fructose are imbibed in a short timespan (e.g. by drinking a soda)
- The liver panics and starts converting these into fat
- Fat buildup in the liver promotes overproduction of insulin
- Overproduction of insulin causes cells throughout the body to become insulin-resistant
- Diabetes
Moreover, there's some theories suggesting that diabetes is a direct contributor to cancer: one route to cancerous cells involves those cells not being insulin-resistant, which causes them to metabolize more blood sugar than normal cells, causing them to be more active in general.
The article makes it clear this is not conclusive evidence; merely strong evidence. Still, you could probably stand to consume less sugar, right? I know I could.