I imagine the perceived gap here is that “those” people understand thermodynamics and the failure to grasp is entirely in your hands.
The solipsistic idea that because your brain has the ability to do X means that everyone must work the exact same way, therefore if my brain is able to do something everyone else must too. If I can sit down and focus, ADHD must just be lazy and choosing not to. If my feelings of hunger are mild and easy to moderate, overweight people must just be weak willed and gluttonous.
To frame this as trying to argue for basic thermodynamics is such a strawman that my pet crow flew out the window in fear. If you think fat people are lazy and refuse to use willpower, and using a drug is a lazy substitute for mental willpower, then say so and have an honest discussion.