Disagree with your disagree. Castrated dogs, cats, and steers get fat. Eunuchs were known for being fat. And it's not just big, calories consumed don't turn into muscle but flab.
Here's a freaky factoid from the first article on Google: "In general, neutered cats require only 75-80% of the food needed by intact cats to maintain optimal body weight."
One could posit that something in Jazz's male brain is telling him that he needs the (checks Google) 2800 calories per day that the average 20-year-old man should eat, but that's at least a third again more than he should be eating. However, eating 700+ fewer calories a day would put him in constant hunger mode. That's a whole damn meal less per day.
Powerlevel but I went vegan for a month after being vegetarian for years and for the whole month I couldn't stop thinking about food, dreaming about food, obsessing about food. And it wasn't any food, it was fatty, greasy food of the kind I don't normally even like. I hadn't eaten bacon in years and it wasn't something I missed at all, but I couldn't stop thinking about it. I'm not a big ice cream fan but I felt like sitting down with a spoon and a pint of ice cream would be the best time. It was affecting my ability to concentrate on anything else. It was what I imagine a pregnancy craving must be like where my body was demanding these particular calorie-dense foods. So of course after a month of being vegan I decided that torturing myself like this was pointless and probably bad for me and I went back to a modest amount of dairy and eggs and the food obsession stopped.
Jazz has serious issues with food, but it's not clear to me how much of it if any is a problem with willpower or character and how much is a problem with biology.