Here is an excellent summary of some of the alternatives to the insane crash-diet-and-exercise mantra that America sells to obese people:
It’s important to have realistic expectations and to be kind to oneself. Cultivating a drill sergeant mentality will not improve quality of life, and isn’t likely to be sustainable.
If there’s one thing that’s consistent in the medical literature, it’s that telling people to eat fewer calories does not help them lose weight in the long term… Many people who use this strategy see transient fat loss, followed by fat regain and a feeling of defeat. There’s a simple reason for it: the body doesn’t want to lose weight. It’s extremely difficult to fight the fat mass setpoint, and the body will use every tool it has to maintain its preferred level of fat: hunger, reduced body temperature, higher muscle efficiency (i.e., less energy is expended for the same movement), lethargy, lowered immune function, et cetera.