19 Jul 2016


There’s no denying that carbohydrates are king when it comes to high-intensity cycling. Climbing Alpe d’Huez leaves your heart beating to the max, and the only way you can get enough energy to working muscles fast enough is by breaking down this essential macronutrient. However, a gramme of carbohydrate only delivers four calories of energy. That compares to fat, which is over double that at nine calories per gramme. If only you could utilise more fat for cycling than carbs…

Preserve Glycogen
There’s an increasing school of thought that if the body is starved of carbohydrate, it’s forced to break down more fats for energy. For endurance athletes like cyclists this is the Holy Grail. Why? Well, your body stores around 1,800 carbohydrate calories in a form called glycogen in the liver and muscle cells before releasing it into the bloodstream in the form of glucose. It’s then broken down in cell powerhouses called mitochondria, one of the results being energy.

The problem is, cycling a sportive can burn up to 800 calories an hour, leaving a shortfall if you rely on carbohydrates, which could result in bonking. However, that’s where fat comes in. Even a fit cyclist stores up to 100,000 calories of fat in muscle fibres and fat cells. So by training with low glycogen levels, your body has no choice but to use fat stores.

To delve a touch deeper into the science, the main adaptation to fasted endurance sessions is enhanced mitochondrial volume in your muscles. That means all the enzymes and sites of aerobic metabolism are unregulated to a greater extent. The phenomenon is known as mitochondrial biogenesis, and as a result of these changes, you become more efficient at using fat for fuel at a given exercise intensity, which means you conserve glycogen for the harder parts of the race.

Moderate Intensity
The key word is ‘intensity’. How hard you train is affected by muscle and liver glycogen levels. If they’re low, so too will blood glucose levels, which’ll make the session feel too tough and could ultimately lead to illness. That’s why it’s appropriate to pencil in fasted efforts during sessions that aren’t too intense.

Measure and plan intensity of session by monitoring your heart rate – check out our feature here

So we’d recommend cycling at no more than around 75% of your maximum heart rate on a Sunday ride that’s no longer than 75 minutes. You should do this after you awake so you’re fasted from the night’s sleep, and only sip water during the ride. This might not sound long but see how you feel. If fine, increase this distance by 15 minutes the following week up to a maximum of 2:30-3hrs depending on fitness. However, always have an energy bar or two on you just in case you feel a touch light-headed.

Finally, if you’re looking to increase intensity slightly during these fasted sessions, you could always knock back an espresso before you clip in to your pedals. A recent study from Australia showed that riders could train harder and still burn more fat after a shot of caffeine.

Drink coffee. Increase intensity. Burn fat. Ride faster!