In my experience its different for different people, a Exercise based way might work for some but not others, a diet alone could be enough for another group, combining the two covers a lot more people in a broad range too adjusting values, most of the time its a pretty simple formula.
Find out how much your body wants to exercise in order to burn off your eating habits adjust your eating around how much you want to be outside walking for, if you want to eat a cake a day have fun on 8 hour walks everyday.. but some people can do nothing and be thin, don't be jealous just understand god hates us all in different ways or satan loves us in different ways, or the space gods ignore us in different ways.