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During the first 24 hours of a fast, within a few hours, the levels of sugar (glucose) circulating in the blood will begin to fall.
When it’s not replaced by food, your body will start looking for energy in the form of glucose that is stored in your muscles and liver, called glycogen.
But once stores of glycogen begin to run low (around ten to 12 hours after your last meal), your body switches into fat-burning mode. It’s called ‘flipping the metabolic switch’. When this happens, fat is released from your fat stores and converted into fatty acids and ketone bodies.
This process is called ketosis. Your brain will use these ketone bodies as a source of energy. The longer you can avoid sugar and cut back on carbohydrates, the longer you should be able to preserve this ketogenic fat-burning state that’s why many of my recipes in this series are lower in carbohydrate than you might expect.
Studies also show that extendimg night-time fast to 12 hours or longer, and crunch your eating time into fewer hours, you can reap even more of the health benefits of intermittent fasting.