I recall Dr. Peat mentioning obese women who could maintain their body mass on 700 calories per day. Hypothyroid individuals can easily become obese because of their very low metabolic rates. Also, starving to lose weight - maybe what is being referred to as "will power" in this thread - tanks the metabolism further. You can't compare a person who can eat 2500 kcal/day without problem to one who can exist on 700 kcal per day. The hypo person is not fat because they are lazy or weak-willed. Do you really think obese babies are downing doughnuts and potato chips with abandon, and thin babies are resisting birthday cake for the sake of their figures? They all eat what they want to, and yet some become obese and some do not. Check out these two genetically identical rats with different prenatal nutrition:
What % of the obesity problem do you believe is based on that video, and what % from lifestyle choices, like what your diet has been for years?