Comment by fastoptimizer

Sugar isn't useless. It gives you energy to function.

If one overconsumes and allows for that useless sugar to circulate, or useless cholesterol, or useless anything from overconsumption, a plethora of interesting metabolic things happen in the body and some of them cause disease.

This is a very nice skeptical stance on how to observe food in this age of non-personalized medicine and nutrition:

https://atheismfaq.quora.com/Is-this-food-healthy