So how does intermittent fasting work?
Let’s take a look at what happens in the body when you go more than 8 hours without food.
We’ll start with the last meal consumed.
0 hours: You eat.
0-6 hours: As your body digests and absorbs your meal, hormones (chemical messengers in the body) and neuropeptides (chemical signals in the brain) are released, helping to move nutrients into cells and tell you technically you have eaten enough.
6-8 hours: Most if not all of your meal has been digested. Now you’re in what’s called the post-absorptive state. Nutrients from the meal are available for your cells to use for energy, repair, or other jobs.
8-12 hours: Your body has largely cleared and used all the nutrients from your last meal. This shift in energy and nutrient use from your meals to whatever that has been stored in your body creates the biochemical changes that define the fasted state.
12-48 hours: Your liver releases ketone bodies as well as stored glycogen, and your liver and kidneys start making glycerol and free fatty acids. These are all substances your body can use as fuel.
48-72 hours: If you’re in the fasted state longer than a couple of days, your body starts to slow or change key physiological processes in order to keep you alive.
72+ hours: By about two to three days into a fast, you’re almost completely dependent on fatty acids released from your adipose (fat) tissue for fuel. In long-term starvation conditions, this helps spare your more valuable stash of protein, which makes up most important body structures, such as your internal organs.
While fasting naturally leads to a caloric deficit, its benefits go far beyond simply “eating less.” It triggers a sophisticated biological “survival mode” designed to optimize the body during periods of scarcity.
Here is a breakdown of how that shift impacts your health:
Fasting acts as a reset button for several key health markers. By giving the digestive system a break, the body sees a measurable drop in:
One of the most profound effects is a process known as autophagy. Think of this as a cellular recycling program; when external fuel is unavailable, your body begins identifying and breaking down damaged components to keep the system running cleanly.
While intermittent fasting often yields positive results for men, it can be a “double-edged sword” for women due to unique hormonal sensitivities.
The female body is highly attuned to energy availability. Hormones governing ovulation, metabolism, and mood are essentially on a “high-alert” system; when the timing or quantity of food intake shifts drastically, this system can interpret the fast as a period of extreme stress.
Disrupting these delicate reproductive signals can lead to a cascade of physiological issues, including:
I wish I could give you a definite answer. The fact is that each our bodies are different and the way how our bodies react to fasting differs from one to another. That being said, fasting definitely has its benefits and you will never know what it does to you until you really try it.
If you need more help, or eager to know how to start, I am offering a personal nutrition coaching to assist you in whatever difficulty you may face. Drop me an email at jin@blackbox.fit to know more!
Train’s goal is to improve quality of life by improving the health of the people in Klang Valley. We are a fitness center dedicated to helping you to reach your fitness goals. Visit us today at our location in Subang Jaya, Selangor.