Carbohydrates are the most important fuels during exercise at intensities above 65 percent of maximum effort. Unfortunately, consuming high carbohydrate diets might trigger weight gain and obesity. Cycling carb intake (carb-cycling) is a nutritional technique that promotes fat loss without decreasing performance. Carb-cycling refers to training when glycogen-depleted to improve fatty acid oxidation (burning fat calories for energy), and increasing mitochondria. Glycogen is carbohydrate stored mainly in the liver and muscles. Mitochondria are the tiny furnaces inside cells that provide energy. Increasing mitochondria improves endurance and enhances the capacity to lose fat.
Carb-cycling works in trained and untrained people. Studies found increased fat burning and glycogen replenishment in elite athletes, recreational exercisers, and unconditioned people.
Carb cycling might give endurance athletes a nutritional shot in the arm:
– Carb-cycling does not decrease endurance.
– It promotes fat burning and helps preserve glycogen- essential stored carbohydrate for high intensity exercise.
– It promotes fat loss.
– It increases fitness with less training.
The Science Behind Carb-Cycling
The technique works by depleting muscle and liver glycogen with an aerobic training session followed by an intense interval training workout several hours later. Interval training is a series of high intensity exercises followed by short rest periods. A typical interval workout is six, thirty-second repetitions on a stationary bike at 100 percent of maximum effort with 2-minutes rest between reps.
Interval training when glycogen depleted is difficult and painful, but it is great for fat loss. While it works well for endurance athletes, it might be inappropriate for power athletes because it reduces training intensity and does not increase lean body mass. However, this method is appropriate for people interested in fat loss or cross training for personal fitness. Carb-cycling increases critical enzymes involved in carbohydrate and fat metabolism and up-regulates genes that trigger fat burning.
Exercising during sugar deprivation causes cell adaptations that promote alternative fuel use. Fatty acids, certain ketones, and even alcohol can serve as fuel for metabolism. Sugar (glucose) is the preferred source of energy during short, intense activity. The cells become more dependent on fatty acids when less sugar is available. Processing fatty acids is slower than carbohydrates, particularly during exercise. Mitochondria cannot speed up the process, so cells meet the increased energy demands by creating more mitochondria. This allows muscles to meet the energy demands of exercise by metabolizing more fatty acids and breaking down
Incorporating Carb-Cycling in Your Training
The technique involves performing high intensity interval training when glycogen depleted. In response, the cells will increase mitochondria and burn more fat.
– Do aerobic exercise, such as running or cycling, at 70 percent of maximum effort for 60-90 minutes. You can promote glycogen depletion by reducing carbohydrate intake for one to two days before the workout.
– Rest two hours. Don’t eat any carbs during this rest period.
– Do an interval training workout, such as running 8-200 meter sprints at 90 percent effort with 2 minutes rest between intervals.
This technique is inappropriate for strength and power athletes because it decreases training intensity by 10 percent or more. This is also a poor training method for people who want to increase muscle mass. However, this is a terrific way lose fat rapidly. Carb-cycling is not a magic bullet for preventing obesity, but it is an effective training method for jump-starting your weight loss program.
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van Loon LJ, Goodpaster BH. Increased intramuscular lipid storage in the insulin-resistant and endurance-trained state. Pflugers Arch, 2006 Feb;451(5):606-16.