After somewhere between three and five hours, your body stops processing its last meal. There's nothing left to absorb, so insulin levels naturally decrease. Then, somewhere between eight and 12 hours after that last meal, your body starts burning stored fat. (Why don't you start burning fat sooner? Biology is sometimes a pain in the ass; it's like our bodies will do anything to hang on to fat.)
“Do what works for you,” Langer says. “And if something doesn’t, change it. There’s a million other ways to go about it. There are no absolutes in nutrition.” Case in point: In a 2018 JAMA study, when more 600 adults who were classified as overweight followed a low-fat or low-carb eating plan over the course of 12 months, everyone lost about the same amount of weight.
Sure, you can lose weight quickly. There are plenty of fad diets that work to shed pounds rapidly -- while leaving you feeling hungry and deprived. But what good is losing weight only to regain it? To keep pounds off permanently, it's best to lose weight slowly. And many experts say you can do that without going on a "diet." Instead, the key is making simple tweaks to your lifestyle.