None of my family members are overweight, and I doubt that anyone in my family wastes enough food for even a small meal in the course of a week (or two). “Stealing from the poor” is a little harsh, but buying excess and then wasting that food increases demand, which does reduce what the very poor can afford to buy.
In a free market, the increased demand would lead to more of a commodity being produced as suppliers competed to meet the demand.
Hunger in the modern world is the result of the political decisions made in the areas where it is a problem. It is not a supply/demand problem and it has no relation to the waste of food in prosperous societies--that is just silly.