What typically happens to the overweight person after a few hours without food is that as they run out of glucose from their last meal, instead of seamlessly transitioning to the fasted state and mobilizing and burning stored body fat, they become HUNGRY for more food. They will spend most of the day trapped in a cycle of eating every few hours, spiking glucose, and then becoming hungry when blood sugar drops.
Humans have the ability to become ‘fat-adapted’ and improve their ability to fuel themselves with stored body fat instead of glucose. However, this takes time and practice, and your body has to do a number of things to slowly increase your fat-burning pathways. This includes improving insulin sensitivity to lower insulin and promote fat mobilization into free fatty acids from the fat cells as well as up-regulating the fat-burning pathways at the cellular level.
The two best ways to improve your fat-burning ability are: Exercise and Intermittent Fasting. High-intensity exercise depletes glucose and glycogen rapidly, forcing the body to switch over and utilize more fat for fuel. Exercise also improves insulin sensitivity. Intermittent fasting, and spending more time in the fasted state, gives the body more ‘practice’ at burning fat.