Fasting and its stages

2 min read
Fasting and its stages
2023 Apr 12Nutrition

Fasting: A Journey Through Body and Time

Losing weight and maintaining a healthy mind and body have several paths, and one particularly notable method is fasting. This practice, often termed 'time-restricted eating,' limits food consumption to specific hours of the day. Although it has recently gained traction in health and fitness, fasting has been introduced previously. It's deeply rooted in history, one of the oldest medical treatments, and significant in numerous religious traditions.

Let's take a look at the phases of fasting.


1. The Anabolic State (0-4 hours)

During this growth phase, the body harnesses the energy from consumed food for power, cellular, and tissue growth. Insulin is released by the pancreas, which processes the glucose in your bloodstream, storing any surplus in cells. Proteins and fats are converted into glucose, amino acids, and fatty acids, with excess glucose becoming glycogen in the liver.

2. Catabolic State (4-12 hours)

Here, the body transitions from building to breaking down. As blood glucose drops and insulin decreases, glucagon—a hormone that regulates blood sugar—emerges. Energy is now sourced not just from carbohydrates but through gluconeogenesis, where glucose is generated from non-carbohydrate sources.

3. Initiated Fat Burning (12-18 hours)

Entering this stage, the body taps into its fat reserves for energy, relying on fat burning and the breakdown of stored glucose glycogen.

4. Active Ketosis (18-36 hours)

At this point, the body predominantly uses fat as its energy source. Ketosis, the breakdown of fat cells to release energy, kicks in, producing ketone bodies that fuel the brain. This phase is marked by increased rejuvenation, healing, and enhanced cognitive functions.

5. Deep Ketosis (36+ hours)

Deep ketosis amplifies the effects of the prior stage. When carbohydrates are depleted, the body burns fat, producing energy-rich ketones. Over prolonged fasting periods, consistent ketosis ensues, insulin and glucose levels remain low, and fat burning intensifies through lipolysis, where fats break down into glycerol and free fatty acids.


Fasting isn't just a trend—it's backed by science, offering remarkable health benefits like weight loss, improved metabolic health, and extended longevity. Always remember to listen to your body and adapt accordingly.

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