What happens when you stop eating?

It is well known that when you eat, your body begins a series of biological processes to digest and use the nutrients found in that food to help you repair muscle, create new cells, and store some of the extra fuel as fat for later use. But it’s not common knowledge, What happens when you stop eating? When you don’t eat the body enters a completely different series of biological processes that are just as necessary and beneficial as the processes that occur after eating.

Also read: What happens to your body when you cut out sugar?

What happens when you stop eating?

Of course, if you don’t eat for long enough the negative effects will start to outweigh the positive effects. But there are myths and misconceptions about exactly what happens to your body when you stop eating. So, in this article, we’ll go over that process step by step based on the scientific evidence. 

Conventional advice about feasting and fasting

First, let’s address the conventional advice which will tell you that it is unhealthy to go for long periods without food. It does not mean days or weeks, here we are talking about simply skipping meals. On the contrary, we have been told that we should eat small but frequent meals.

The truth however is that there is nothing natural about eating five or six meals spread out evenly over the hours that you’re awake every day. This is because throughout our evolution we didn’t always have access to food. So, you could claim that the fasting and feasting eating cycle is more natural than eating breakfast, lunch, and dinner, every single day. 

Fasting for certain period can benefit your health

Because our ancestors had to cope with cycles of food shortage and food abundance we’ve developed metabolic pathways that help us cope with prolonged periods without food. Fasting for certain periods can benefit your health rather than hurt it. But it doesn’t feel that way because one of the first things that will happen when you stop eating is you’ll start to feel an unpleasant feeling of hunger. 

The intensity of this feeling of hunger highly depends on how accustomed your body is to burning fat for fuel. You see, most people regularly eat a high-carb diet. So their body relies primarily on glucose for energy, instead of using fatty acids or ketone bodies. Your body can store a lot of fatty acids in the form of body fat and those fatty acids can be used for energy at a later time when food is scared by converting the acids into ketone bodies in the liver. 

But with glucose, it is an entirely different story. Your body can store a very limited amount of glucose in your muscles and liver for future use and this amount gets depleted after fasting for only about 24 hours. But depending on how many carbs you eat regularly it can take as little as 8 hours or up to 48 hours. 

What happens if your body isn’t effective at buring fat for fuel

After that point, your body will have to rely on a different energy source in the form of fat. And if your body isn’t effective at burning fat for fuel, this will likely lead to severe cravings, especially for high-carb foods. 

If you trained your body to use fat for fuel by following or low carb diet, a keto diet, or you’ve gone through long-duration fasting in the past. Then you won’t experience the same severity of hunger cravings. Many people that fast frequently don’t experience hunger at all. This isn’t only because their body is used to burning fat for fuel, but it is also hunger levels increase at the times of the day that you normally eat. 

How we get hungry?

This is due to the hunger hormone Ghrelin. Which has the effect of stimulating your appetite when it is released. So during those first 24 hours that someone will stop eating. Studies show that Ghrelin will spike automatically for most people around the time of the day they typically have breakfast, lunch, and dinner. And that spike will make you feel hungry. 

However, if you are someone that already become accustomed to fasting every single day, you won’t experience the sharp spikes and Ghrelin during your fasting window. That means you won’t feel as hungry as someone that’s used to more meals throughout the day.

But, even if you used to breakfast, lunch, and dinner. You should know that the data shows us that the spike in Ghrelin is short-lived. If you just ride out that hungry feeling that you get within about two hours from the initial spike in Ghrelin. It should draw back down to normal levels and your appetite will drop down as well.

What leads to weight loss?

After about the first 24 hours, your body will burn through your remaining glycogen stores and switch almost entirely over to burning fat for fuel. Which will slowly lead to weight loss. Since your brain primarily relies on glucose to function. Your body will be able to separate Triglycerides that come from your fat stores into Glycerol and Free Fatty Acids. 

While the free fatty acids can be used immediately for energy, the glycerol can be sent to the liver where it can be converted into glucose through a process known as gluconeogenesis. And that can temporarily supply the brain with the glucose it needs without breaking down muscle tissue just yet. 

The negative side of fasting and weight loss

Contrary to popular belief, your body will reduce its protein breakdown rates substantially after just 24 hours of fasting to try to prevent muscle loss during these initial stages. During this time you will start to feel cold as well since your body temperature will be lower from not digesting food and a lower thyroid function. 

As you fast for more and more days, the pounds of fat lost will start to add up. For example, we have a study on a 27-year man that didn’t eat for longer than a full year. He did this under the supervision of doctors that had him living on multivitamins in combination with yeast for 382 days. And he only drank water, coffee, tea, and diet soda the entire time. 

During that time his body weight went from 456 pounds to 180 pounds. So by not eating he was able to lose about three-quarters of a pound per day. Even though this is a crazy achievement, for the average person, doing something like this is extremely risky. And going 382 days without food can certainly lead to death. 

The man in this study was severely overweight. This is why he was able to survive by using all that excess fat for energy. Also, he was under the supervision of doctors, that gave him the right supplements so he could survive. 

Gluconeogenesis

But for most people, after just a few days of not eating, you won’t only be using body fat. But you’ll also lose a lot of muscle mass. Especially if you are already relatively lean. That’s is because if you don’t have a lot of fat, your body is more likely to convert protein into glucose through that same process as before known as gluconeogenesis. 

Muscle loss shouldn’t be as big of an issue until about 72 hours after you stop eating. Because during those first few days, your body will be able to get the energy and the glucose it needs, mostly from your body fat your body will also ramp up your human growth hormone levels as an anti-starvation response. 

The growth hormone will assist with the release of fat from fat cells. And it will help stimulate fat oxidation, in general, this also helps spare amino acids and preserve muscle mass during the first couple days that you’re not eating. 

It’ll take about 3 days to start losing muscle mass

Of course, muscle loss can start happening even sooner than three days if you’re already really lean. But on average it’ll take about 3 days. The longer time length that you go past those three days without food. The more your muscle loss will accelerate. For example, when a slightly overweight man only drank water for 44 days. By the end of his fast, he reduced his weight by 25%. 

This would have been an absolutely amazing outcome if at least ⅔ of that weight wasn’t muscle loss. Going for some time without food not only impacts your body weight and your physical appearance but the food deprivation will also set off a unique series of metabolic events. 

Autophagy

For example, after the first couple of days, your body will also activate a sort of cellular cleanup process known as autophagy. Autophagy is like a recycling process where your body gets rid of the dead and dysfunctional cells and turns that waste into materials that can be used for growth and repair. 

This helps reduce inflammation throughout the entire body which helps fight some diseases. These benefits will also extend to your skin cells potentially slowing down wrinkles, age spots, and acne. Your immune system will also improve thanks to autophagy. Your body will produce brand new white blood cells which will be stronger at fighting diseases. 

Unfortunately, these positive effects on your immune system will come crashing down when you go longer than just a few days without food. This is because not eating for a few weeks will slowly start to lead to malnutrition. And your body won’t have access to the vitamins and minerals that it needs to maintain a strong immune system. 

Starvation increases the risk of infections

This is why research shows that starvation increases the risk of infections. For example, the same man from before that mostly muscle by fasting for 44 days straight and only drinking water, developed several nutrient deficiencies including a deficiency in thiamine, riboflavin, and vitamin K. 

So, a few days without food and your system is likely to get a boost. But a few weeks without food and you’ll be much more susceptible to disease and infection as time passes further without food. Your body will continue breaking down the last of its muscle, fat, glucose, and even bones until it is forced to start slowing down or shutting down your organs to save energy. 

At this point, many of the opposite effects of autophagy have fully kicked in. For example, you can lose hair, develop brittle nails, have frequent infections, and have trouble healing wounds. Just like with autophagy, your brain will also go through a roller coaster ride, during this process. 

Neurogenesis in the brain

When you fast for just a few days they’ll be a rise in the rates of neurogenesis in the brain, which is the growth and development of new brain cells and nerve tissues. Higher rates of neurogenesis have been linked to increased brain performance and improved memory, mood, and focus. 

While fasting, you’ll begin producing more protein in your brain and one of these important proteins is known as BDNF. Which has been referred to as miracle growth for your brain. This protein assists with the production of brain cells and even helps protect your current brain cells while improving memory and learning as well. 

Unfortunately, just like the other things, the longer you fast, the more these positive effects start turning into negative effects. If you don’t eat for a long enough timeline to where your body has already broken down a significant amount of fat and muscle, it will become harder and harder for your brain to function properly. 

Brain metabolize its gray matter

Remember, your brain runs off of glucose. Without eating something, converting protein and fat into glucose through gluconeogenesis will only get you so far. At some point during the starvation cycle, if you go long enough without food, your brain will only metabolize its gray matter. 

Literary shrinking of the brain, just to stay alive. Towards the end, your body will do this with your heart and your other organs as well. Ultimately, if you still don’t eat given enough time, you’ll die most likely from organ failure. 

Exactly how long does it take is unknown, because it is unethical to study the starving population. Even though some sources estimate that you won’t last longer than two months without food. It can take more or less time depending on how much body fat you have to spare for energy. 

Conclusion

So overall, not eating for a short time length ranging anywhere from 16 to 72 hours can be very beneficial for fat loss, productivity, immunity, and for your brain. But when you don’t eat for longer than 3 days you’ll start to experience negative effects like muscle loss, and as you go for weeks or months without food. That’s when everything from organs to muscles to bones to brains and your immunity all goes rapidly downhill. 

So that’s what happens when you stop eating. If you have gotten some valuable insights from this article make sure to share this article on social media.