“Is obesity a metabolic disorder?”

It is, in a way, a metabolic disorder. Much like different engines in cars have a different "miles per gallon." Many of us, including myself, are built to go longer distances and burn less fuel (i.e. like a hybrid vehicle and goes 50 miles to the gallon) unlike some of my friends who burn more fuel at 10 miles to the gallon. This is why there is no such thing as calorie and calorie out that applies to everyone across the board. The best way to fix it is to cut out carbs which the body stores as fat and focus on getting healthy protein and healthy fats (within reason). I also recommend that you work with a good bariatrician in your area to help with medications, if needed, to help the body burn more fuel rather than keep you like a hybrid car. Go to the following website and search for a bariatrician in your area to help: https://obesitymedicine.org/find-obesity-treatment/