The low carb flu commonly occurs during a metabolic transition that takes place in your body from being carb/sugar dependent to becoming fat (and protein) dependent.  It can take anywhere from 2 - 6 weeks for your body to adapt to efficiently converting fat into energy.  Since this energy pathway is a little more complicated, it takes your body a little time to get it running up to speed.

But the great thing is, once your body is fully “fat” adapted, you’ll be much more efficient at burning fat!  On top of that, being fat adapted is also good for your brain.  Your noggin’ functions very well on ketones which are fat metabolized byproducts in absence of glucose.

It may sound a little “sci-fi”  but the truth is we’re all born with a certain genetic make up and although we can’t change our genes, we can heavily influence what genes get expressed.

For instance, let’s say you’re a former cardio junkie and a sugar addict (like many “fit” people…myself included!).  Your body was programmed to use all of the necessary metabolic pathways needed to convert carbs for energy, so you can continue engaging in long duration exercises.  In other words, what you did (excessive cardio) and what you ate (high carb diet) determined what genes got expressed.  Unfortunately, these metabolic pathways happen to be efficient at burning glucose but poor at burning fat.  Hence the constant struggle to keep weight off, even though you’re incessantly running, spinning and doing anything cardio related for hours on end.

However, being on a low carb diet, you’re essentially turning OFF the genes responsible for your metabolic pathways that convert carbs for energy and turning ON the genes that activate metabolic pathways which convert fat to energy instead.  And when you shift your body from being carb dependent to fat dependent, you’ll be able to burn fat easier without having to exercise more, because you’ll be utilizing it as your primary source of energy.

If you’re confused… don’t worry, it’s a bit technical, but all you really need to know, is that being on a low carb diet and going through the “low carb flu” is worth it, because in the end, it will make your body much more efficient at burning fat.

As for exercising on a low carb diet, there are essentially 2 optimal ways:

1. Short, high intensity workouts
2. Long duration low intensity workouts

The short intense workout will NOT use your fat for energy during your workout, instead it will use your glycogen for energy.  However after the workout, the energy deficit created during the workout will be supplied by your body fat.  So the greater the energy deficit (...or the more effort you put into your workout) the more you’ll burn fat for energy afterwards.

On the other hand, the long duration low intensity workout, will use your body fat for energy.  The key here is that you don’t train above a certain threshold.  If you work too hard, you’ll automatically dip into your glycogen stores for energy and burn less fat.  This workout is also time dependent, which means the longer you can workout at a low intensity, the more fat you’ll burn.  Believe it or not, this workout method is actually pretty difficult to do, since most people who run or do other endurance activities are used to training at a much higher threshold.  You really need to hold back your effort, if you want to maximize your fat burning potential. A recommended activity for this type of workout will be exercises like walking, hiking or easy biking riding.

Now personally, I don’t have time to spend hours walking or hiking during the week.  This is why I prefer short high intensity workouts that I can do in 20 - 30 minutes and maximize my fat burning potential.  I think doing long easy hikes or bike rides on the weekends, when you have more time may be the best combination.

The “low carb flu” is definitely not pleasant, but as I mentioned before, it’s temporary and the results are well worth it.  However, if your symptoms are too much to handle, try adding a little more carbs into your diet.  It may only take an additional 25 grams of carbs to help you get over your symptoms.