Working Out On An Empty Stomach Burns More Fat?

January 28, 2013

This question has been the subject of much debate in the fitness world for quite some time.
On one side some suggest that exercising on an empty stomach is more effective as it forces the body to use fat stores for fuel, resulting in a greater weight loss.
Conversely, others claim that exercising in a fasted state doesn’t offer any benefit and may even work against you. They point out that the body burns roughly the same amount of fat regardless of whether the stomach is full or empty; but, in addition, by exercising in a depleted state your body will also burn muscles for energy, not only fat.
So who’s right? Who’s wrong?
A newly published study has found that people can burn up to 20% more body fat by exercising in the morning on an empty stomach1. Have we finally reached an answer? Not so fast.

The Study

Researchers from Northumbria University in Newcastle in the UK, sought to find out whether the known benefits of exercising after an overnight fast were undermined by an increased appetite and eating more food later in the day.
The academics asked 12 physically active male participants to perform a bout of treadmill exercise at 10am, either after they had eaten breakfast or in a fasted state.
They discovered that those who had exercised in the morning did not consume additional calories or experience increased appetite during the day to compensate for their earlier activity.
More importantly, they found that those who has exercised in a fasted state burned almost 20% more fat compared to those who had consumed breakfast before their workout.
They concluded that performing exercise on an empty stomach provided the most desirable outcomes for fat loss.
"Our results show that exercise does not increase your appetite, hunger or food consumption later in the day and to get the most out of your session it may be optimal to perform this after an overnight fast” one of the lead authors commented.
Similar outcomes were reached in another study conducted in October 2012 at Glasgow University in Scotland. Researchers found that people who exercise before breakfast used up 33% more fat than those who exercised after eating. They also registered a drop in the blood fats responsible for heart disease2.

Not everybody agrees

Other studies suggested opposite results. In particular, a report published in Strength and Conditioning Journal concluded that the body burns roughly the same amount of fat regardless of whether you eat before a workout3.
Moreover, a separate study published in 2002, found that healthy women who consumed 45 grams of carbohydrates before their workouts ended up eating less throughout the remainder of the day4.


So, what we can do about it? Shall we exercise in a fasted state or not?
First off, let’s stress out that the biggest difference is between doing something and being a couch potato.

But if you’re going to exercise, it seems that there is a slight advantage in doing it on an empty stomach.
Provided that: (i) you don’t compensate this by overeating later during the day and (ii) that you
can actually workout on an empty stomach without feeling dizzy, drowsy or fainting.
If you need to much on a granola bar before a spinning class or have a slice of toast before your morning run, do it. What really matters is that you exercise.
If you can manage to do it in a fasted state consider it as the icing on the cake.
Just remember that weight loss is a slow process that entails a lot of discipline and patience.
As long as you keep at it results will show.

The Iron You



  1. Super interesting, thanks for sharing!

  2. Doing some research on this at the mo, great post!

  3. Very interesting, don't think I could work out on an empty stomach, I really think I would faint

    Please come and check out my latest post if you have a few minutes spare :)



  4. The first time I tried fasted exercise in the morning (light HIIT, with plenty of rest between sprints), I felt so exhausted that I gave up at once, and assumed you NEED to eat something in order to be able to perform. But now I have discovered black coffee; it nicely does the trick of giving you "energy" without the calories.

  5. First of all, a study of twelve people is not a study. They've fallen victim to the error of a too-small sample size.
    That being said, I do think that working out on an empty stomach does give you an advantage. People think they will go into a catabolic state and start passing out if they haven't eaten for a couple hours. It's ridiculous. You don't start actually burning muscle until at least 24 hours into a fast. The human body is far more resilient than people give it credit for. It's not going to shut down on you if you go for a run without packing carbs into it.

    1. "The human body is far more resilient than people give it credit for..." well said Sarah!

  6. Personally, working out without food in my stomach is what works for me. I have tried having breakfast prior to working out and I just feel heavy and bloated but noshing afterward makes me feel as though I am fueling my muscles! Everyone is different though, so everyone needs to just experiment.

  7. For me it will always boil down to what allows me to push myself the hardest. Having done intense physical activity both on an empty stomach and in a fed state, the empty stomach is a much better decision. I have never known anyone who performed better or did more work in a fed state.

    The sample size, as pointed out by the clearly intelligent Sarah Ochocki, is far far far too small to reveal anything. From such a small sample you are far more likely get an extreme of the data than anything that resembles an actual reflection of physical outcomes of a larger population. Stuff like this should always be FOR SCIENCE! Unfortunately people take distinctly non scientific things and treat them as science. When push comes to shove, it will boil down to the individual and how they feel about it.

  8. I personally tried both and basically did it according to how my body felt. I always listen to my body and some mornings I kick ass with black coffee and workout on an empty stomach, other days I prefer to exercise in the evening also as a form of relaxation after work. I went from 27% body fat down to 22% in 4-5 months, so about 1% a month and I keep going at this rate. It's a sustainable strategy and I know I won't go back. As mentioned in the article, the main difference is between doing something and being a couch potato.

  9. I have never looked more cut or been as fit as I am today. At 56 and 5'6" I weight 110 with strong body and very defined muscles. I do a 20 min run or stair master warm up followed by 15-20 HIIT and 15 min weight training everyday on a fed state. I tried empty stomach and didn't have the energy for this type of workout and I was never as fit or defined. So for me it's a fed state. I'm a huge believer that your car won't run without gas and that applies to myself "no energy without fuel". I don't do the whole carb thing in the morning or ever as a matter of fact. A simple chia pudding including collagen peptides, clean protein, erythritol (sugar sub) almond milk, super greens and raw cocoa gets me going, oh and I always start my day with freshly squeezed lemons (2) with warm water as a detox. And of course coffee with almond milk. But hey, you do what works for you just get up and move !!!!!