Deplete your glycogen stores
A study in the Journal of Applied Physiology showed that people who worked out twice a day and did not eat for two hours after their first session (thus depleting carbohydrate stores) were able to burn fat better with no loss in performance, compared to a group that trained only once a day and ate carbohydrates after their session. Another study subjected participants to high-intensity interval training on a bicycle while deprived of carbohydrates. They showed better fat burning and an increase in the enzymes responsible for fat metabolism, again with no loss of performance.
So, how do you achieve the glycogen depleted state? One option is to train twice a day without refueling after the first session. The second option is to do a long training session on an empty stomach in the morning.
Stop using sugar to fuel endurance activity
The usual advice is to take an energy gel 15 minutes before activity, and then one every 45 minutes. What this does is the first gel spikes insulin 15 minutes before the activity which shuts down fat burning and leads to glucose dependency for the duration of the exercise. This is the opposite of what we want when trying to improve our fat adaptation. There is a time and a place for fueling during exercise and that’s at the highest level of racing. But even team Sky’s riders work on their fat adaptation during off-season, so that they are able to use both their own body fat and external fuel as energy sources when the race day comes.
When you’re at the beginning of your fat adaptation journey, it is good to keep in mind that exercising in glycogen-depleted state could cause your body to start catabolizing lean muscle tissue for glucose production. If you want to be on the safe side, consider taking some amino acids during your workouts.
How do you know if you succeeded?
As a fat adapted athlete you won’t need extra carbohydrates to fuel endurance-type activities. If you live the fat adapted life and train in a glycogen depleted state, your body will learn to do moderate intensity activities on plain water alone. It’s not possible to store more than about one or two hours worth of energy as glycogen, whereas you will be able to go for 6 hours easily just on your fat reserves. That’s when you know you are truly fat burning.