>The added benefit of the "exercise first" approach is that after exercising, I find that I don't even want the donut.I'm guessing this approach is something like swapping dopamine triggers. You get a good rush from exercising such that you don't need a dopamine release from eating a donut.
However, I still believe your and RyanMcGreal's anecdotes are the minority. Most obese people do not find exercise to be pleasurable. Getting sweaty is "work". For these people, if they exercise, they'll end up getting hungrier which triggers more eating and the end result is a weight change that nets to zero. In contrast to your scenario, instead of skipping the donut after exercise, they feel that they can "reward" themselves with a donut because they had the discipline to exercise!
For most people, switching out bad food for good food such that they are satisfied without starving is a far easier and more realistic lifestyle adjustment. To be clear, I'm not suggesting people eat "less", but that they eat "differently". Drink a kale smoothie instead of a glass of sugar-laden orange juice, etc.
Telling obese people that exercise will strengthen their heart is more truthful than selling it as a key to weight loss.