Morbidly obese people always have mental health problems, and that's why we eat so much, we are addicted to carbs, etc.
If the mental problems are not fixed, even if you lose weight for a while you won't be able to change your habits long term and you'll regain the weight again.
I'm a binge eater, which is the most common eating disorder on the DSM-V (before V it didn't have a name, but it's actually the most common eating disorder on the general population). My most successful and easiest weight loss involved antidepressants and a shrink, and I managed to keep the weight off for a whole year (longer than ever before). Once I stopped taking the pills and the effect wore off, I started having binge problems again.
Also, even if we lose the weight, most of us end up with loose skin which due to social stigma causes a lot of mental problems linked to general depression and suicide