Hi friend,
If you wouldn't joke about cancer, don't joke about diabetes.
Diabetes, particularly type 2, is "funny" in a way that other health issues aren't because it's associated with fat bodies.
Making jokes about sugar and diabetes is a good example of the just-world fallacy. If people can convince themselves that diabetes is a punishment for a "bad" body or "bad" choices, then they can believe that their "good" bodies or choices will protect them.
It's also an excellent example of the way weight stigma hurts everyone, even people in thin bodies. A person who believes that diabetes is a punishment for fatness is less likely to have their own symptoms checked out or pursue treatment if they do develop diabetes -- both due to not believing that they could have it, and the shame of being associated with a stigmatized condition.
Make no mistake: that stigma kills people.
Because when you stigmatize a health condition, the people who suffer from it receive less and worse-quality care for it. Stigmatizing a condition associated* with an already-stigmatized population compounds oppression. Please stop.
*We do not currently have any peer-reviewed evidence showing more than a correlation between fatness and diabetes. Correlation is not causation. Thin people get diabetes, too.
To the best of our current knowledge, diabetes is primarily a genetic condition and is not caused by your body size or what you eat.