Expert Claude C Butler Explains:

Our body relies on two fuel sources—carbs (in the form of glycogen) and fats, to power energy into our muscle contractions during any strenuous activities including exercise. It is believed that moderate intensity workouts consume about 50–60% of energy from glycogen and the rest from fats.

The “Fasting before workout” principle:

Believers of this philosophy suggest that you deplete glycogen stores by fasting overnight, or going several hours without refueling, triggering fatty acids to be used as replacement for low and moderate intensity (cardio) workouts. Carbs are pulled in as the workout intensity increases.

Upside: More fat burn during low and moderate intensity workouts.


– Fat burn doesn’t happen immediately but over hours and sometimes days and the more carbs you burn (with high intensity workouts) the more fat you burn post it. Studies have proved that the more fat (not carbs) you burn during low intensity workouts leads to lower fat burn the rest of the day. So its important to burn more carbs and less fat during workouts which can ONLY happen with higher intensity short-burst workouts.

– Glycogen powers your high intensity workouts and is vital for endurance. Depleted glycogen stores (in muscles and liver) will compromise your energy output, leading to fatigue, lack of coordination, light-headedness and lack of concentration commonly known as “hitting the wall”. The secondary energy source- fat simply can’t be metabolized fast enough to support the higher pace.

– Your body can store glycogen for 12 to 16 hours before needing a recharge. Low levels direct the body to get energy, through glucose breakdown, from your MUSCLES (not fat as everyone believes). Muscle burn is a trigger to your body to store more fat. Muscle mass is critical for fat burn post exercise.


– Early in the morning, grab a protein shake, piece of fruit, or smoothie… to charge your body energy sources to boost workouts as.

– For morning exercisers, eating a normal dinner, the night earlier, is good enough to allow glycogen levels to be low enough to burn fat during exercise and high enough to take you through your routine. Don’t FAST.

Always choose energy and sustainability over anything else. 




Related Posts