I didn't grow fat because I have a slow metabolism (and I do), or because I'm addicted to a specific unhealthy type of food; I'm fat because I made a major switch in lifestyles (hard labour to desk job) without any changes to my diet, and because I kept prioritizing other things than my health for decades. After a while it became obvious that change is needed, but boy is it difficult to lose weight once you've had it for 20 years!

The solution is managing my diet. Sure, some variables may change (such as chemicals affecting my body), but I still need to keep consuming less calories than I burn in order to do something about the issue.