Does Your Body Burn Fat Or Muscle First When Fasting?

Does Your Body Eat Fat Or Muscle First When Fasting?

We have been doing some recent experiments with fasted hiking and the results have been good so far. However, one area that I am a little concerned about is that I don’t want to lose too much muscle mass.

I haven’t shown any concrete signs of muscle loss to date, but maybe that is too be expected with only completing a couple of fasted hikes. I have noticed that my hiking friends that have been fasting for a long time have a lot less muscle than me. Is there a correlation because of the fact that they fast here, or is their lack of muscle mass just a coincidence? Let’s dig a bit deeper to find out.

When Fasting for over 12 Hours, which is Burned First, Fat or Muscle?

Does Your Body Burn Fat Or Muscle First When Fasting - Fat or Muscle

The clear answer here is Fat. It appears that it is almost impossible to find any evidence that your body will start to burn any muscle whatsoever if you are intermittent fasting. Certainly not if you are only fasting for somewhere between 12 and 16 hours at a time.

The whole reason that your body stores fat, is so that it has an “on demand” store of energy to call upon when your Glycogen is depleted. Why would it burn muscle and potentially damage the structure and integrity of our body if it wasn’t in a life or death, survival situation, which intermittent fasting for short periods of time is not.

However, at around the 12 hour mark of fasting, if we haven’t been exercising (sooner if we have), our body will begin to burn fat as our Glycogen will be depleted.

Do you Gain or Lose Muscle with Intermittent Fasting?

Does Your Body Burn Fat Or Muscle First When Fasting - Build or Lose Muscle

While Intermittent Fasting will make you lose fat, there are a body of supporters who claim that Intermittent Fasting will also make you lose muscle, this is simply not true and has been misinterpreted from stories where people have been lost and in a life or death starvation situation.

If we are intermittent fasting and not doing any form of strength or resistance training, we will neither gain or lose muscle, but we will lose fat.

If we are doing strength and resistance training in order to try to build muscle mass, then following an Intermittent Fasting is not really suitable. Studies have shown that building muscle on an Intermittent Fasting Diet is close to impossible, but maintaining Lean Muscle Mass without losing it is.

Is there a Link between Fasting and Muscle Loss?

Does Your Body Burn Fat Or Muscle First When Fasting - Muscle Loss

There is a link between Fasting and Muscle Loss, but we have to be clear on what we are talking about here.

As long as we aren’t fasting for periods of significantly more than 24 hours, we aren’t going to be experiencing muscle loss. Most Intermittent Fasting Plans follow the standard 16:8 Plan, which appears to be the most popular form of Intermittent Fasting, where you fast for 16 hours and take all of your meals within an 8 hour window.

Following a plan such as this will mean that is is extremely unlikely that you will experience any loss of muscle mass when fasting.

How can I Burn Fat and Not Muscle when Intermittent Fasting?

As mentioned above, the best way to ensure that you burn fat and not muscle when fasting is to ensure that you keep your fasting periods to around or below the region of 24 hours, which most popular forms of modern fasting do.

Lessons Learned from a Year of Intermittent Fasting

Does Your Body Burn Fat Or Muscle First When Fasting - Lessons Learned

I came across this excellent article written by James Clear on the results of him completing a year of Intermittent Fasting. It is well worth a read and you can pick up a Quick Start Guide there too. Here are the bullet points:

  1. The biggest barrier is your own mind
  2. Losing weight is easy
  3. Building muscle is quite possible (if that’s what you want)
  4. My best work is usually done when I’m deep into my fast
  5. For best results, cycle what you eat
  6. Like most things, you should take a long–term view of eating
  7. It’s strange, but when I’m fasting I want food less
  8. Losing fat and gaining muscle can both be done, just not together
  9. When fasting, I have made more gains by training less
  10. As long as you stay under 50 calories, you’ll remain in the fasted state
  11. Prepare to drink a lot of water
  12. The best diet for you is the one that works for you

It really is a quite enlightening read, I suggest you check it out if you have time.


Where do People Lose Weight First?

Does Your Body Burn Fat Or Muscle First When Fasting - Where From First

To be honest this question is not one that I’d really considered, or been concerned with to be honest. However, a couple of people have mentioned it, so I thought I’d look it up and include it here.

It appears that there is no solid evidence to prove that any two people will lose weight first from the same place.

The evidence points to the answer for each individual as to where they will lose fat from first is down to their own genetic makeup.

A cruel and frustrating unwritten rule appears to be that the area that you are most prone to put on weight (store fat) first, is the last place that you lose it from.

What is the Starvation Response?

During my research I came across the Starvation Response a few times, so thought I’d look it up and explain what it was on here:

Ordinarily, the body responds to reduced energy intake by burning fat reserves and consuming muscle and other tissues. Specifically, the body burns fat after first exhausting the contents of the digestive tract along with glycogen reserves stored in liver cells and after significant protein loss. After prolonged periods of starvation, the body uses the proteins within muscle tissue as a fuel source, which results in muscle mass loss.


Where does the Body Fat go when we Lose Weight?

Now that we have clarified that we are going to lose fat first and foremost if we Intermittent Fast, where does the fat go to? I’m sure it doesn’t just melt like candle wax and run down to our ankles. So what happens to it?

It seems the answer is a little more complex than I thought. What I have just read is pretty complex, so I’ll break it down into Layman’s terms.

We break the fat down into energy and waste products. And as Einstein so eloquently stated: “Energy cannot be created or destroyed; it can only be changed from one form to another.” (Who am I to argue with Einstein?).

Does Your Body Burn Fat Or Muscle First When Fasting - Einstein and Monroe

We must be converting that Energy into something. We are converting it into Energy and Waste Products. The potential energy from the Fat Cells gets converted into Heat Energy as we use our muscles and bodily functions. This heat then dissipates through our bodies.

The waste products in its three forms of matter, liquid, solid and gas then get secreted by our bodies through:

  • Liquids – Urine and Sweat
  • Solids – Faeces, when we use the toilet
  • Gas – Breathed out as Carbon Dioxide

So, there you have it. A finely tuned machine running efficiently on Fat. We sweat it out, pee it out and breathe it out.