I think their point is that doctors don’t want their patients to become entrapped by obesity into lifelong poor health, which also traps them as sources of revenue for corporations that profit from sickness and fat: pharma, companies that sell fad diet and/or exercise plans, etc. So if your doctor tells you to lose weight, it’s probably coming from a good place, regardless of what else might be going on with your health.
(And just in anticipation of some replies I might get: yes, it’s absolutely a real and shitty thing when doctors only see the fat and assume it’s the cause of all the patient’s problems. You deserve better healthcare than that. But also recognize that while the fat might not be the cause of a given problem, it might be exacerbating that problem.)
This is a recent problem. Do we think those purported fat genes just evolved in society over the past eightyish years, and spread so widely that, per the 2017-2018 NHANES data, 73% of American adults are overweight (30.7%) or obese (42.4%)? On a population level it’s clear this cannot be genetic. There’s been a cultural shift that has caused this problem, often thought to be related to processed food, less time to cook, and for some underserved communities, food deserts.
Look at how dramatically obesity has risen since the '80s: