You fuel your workout with carbohydrates, fats and protein, but carbohydrates are the body's preferred energy source. The body automatically seeks out carbs first as they are easiest to burn. In the absence of carbs, the body burns fat and then protein. The amount of carbohydrates burned during exercise depends on the type, duration and intensity of the exercise.
Simple Vs. Complex
Complex carbohydrates, such as oatmeal, sweet potatoes, potatoes, yams, whole grain rice, whole grain bread and whole grain pasta, provide slow-release energy. These carbohydrates are broken down and stored in the liver or muscles as glycogen, which is ready to be used to power your workouts. Simple carbohydrates from refined grains such as white rice, white bread, packaged breakfast cereals, fruit juice, sugar and honey break down swiftly into glucose and provide quick energy. If this energy is not going to fuel exercise, it becomes a surplus; it is transported by insulin to your fat stores and can result in unwanted weight gain.
Fuel for Intensity
Carbohydrate in the form of glycogen is stored in the liver and muscles. It is the primary source of energy for short, intense bouts of exercise such as weightlifting, sprinting or explosive activities that involve rapid contraction of the muscles. If glycogen stores become depleted, a sports drink that contains simple carbohydrates can deliver the carb energy you need. The body will quickly convert the carbs into glucose to be used by your muscles.
Between 50 and 60 percent of energy used in low intensity cardiovascular exercise comes from fat. Carbohydrates are mainly used during the first few minutes. The website ExRx.net says it takes 20 to 30 minutes of continuous cardiovascular exercise to use 50 percent carbohydrates and 50 percent fat. If you increase the intensity, such as incorporating short bursts of sprinting into a 30-minute jog, the energy contribution from carbohydrates increases as your muscles contract harder and faster.
Your muscles continue to use carbohydrates, stored in the muscles and liver as glycogen, for energy during cardiovascular exercise. Once you've burned your glycogen stores and tapped into the fat, your muscles will be compelled to use protein as energy, which will eventually lead to a loss of muscle tissue. If you intend to do long cardiovascular sessions, eat plenty of complex carbohydrates a few hours before you exercise. This is called carb-loading and helps ensure you do not use up your stores of glycogen during prolonged periods of exercise.
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This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.