I think the most sustainable way to lose fat (not weight ofc) is to gain lean muscle mass. You can substantially increase your basal metabolic rate and induce a calorie deficit to incur fat loss without actually eating any less. The problem of course is that your body does automatically increase your appetite commensurately as your BMR goes up, but calorie counting + discipline can help you stay lean as you gain muscle mass, and then lose the fat over time.