From zero to 24 hours, here’s what happens inside the body when you fast

Here’s what occurs:

0-4 hours: Immediately after eating, the body focuses on digestion and absorbs nutrients. “Blood sugar and insulin levels rise, providing energy,” shared Dr Maneendra.

4-8 hours: As digestion completes, blood sugar and insulin levels drop. Dr Maneendra, said that the body uses glycogen (stored glucose) in the liver and muscles for energy.

8-12 hours: Once glycogen stores deplete, the body uses fat for energy. According to Dr Maneendra, this is called ketosis, where fatty acids are converted into ketones, fueling the brain and muscles.

Here’s how fat loss happens (Source: Freepik)

12-16 hours: The body continues in fat-burning mode, and ketone levels rise. “Growth hormone production may increase, aiding fat breakdown and muscle preservation,” shared Dr Maneendra.

16-24 hours: Autophagy begins when cells start to repair themselves by breaking down and recycling damaged components. Dr Maneendra explained that inflammation reduces, and the body focuses on cellular maintenance. “Autophagy is the body’s way of cleaning out damaged cells, in order to regenerate newer, healthier cells. Reducing your daily calorie intake by 10–40 per cent can trigger autophagy,” shared Parmeet Kaur, head and chief nutritionist and dietician, Marengo Asia Hospitals, Gurugram.

Kaur further shared that autophagy may increase in activities that cause stress to the cells, such as a lack of nutrients during prolonged fasting for two to three days.

24+ hours: Ketosis deepens, and autophagy increases. “Insulin levels drop significantly, promoting fat loss and enhancing the body’s ability to manage blood sugar,” shared Dr Maneendra.

However, Dr Maneendra said fasting longer than 24 hours should be done with medical supervision, as it can lead to nutrient deficiencies and other complications.

DISCLAIMER: This article is based on information from the public domain and/or the experts we spoke to. Always consult your health practitioner before starting any routine.