The speed with which food supplies your body with energy depends on how fast your body digests and metabolizes it. Carbohydrates are the most quickly digested macronutrient, while proteins and fats take longer to digest. Within the carbohydrate group, simple and complex carbs differ in processing times. Simple carbs are the most quickly metabolized and provide the speediest source of energy for your body.
Digestion and Energy Production
Your body uses various nutrients from foods to create energy. It can use protein and fat for energy, but if carbs are readily available, they take precedence. When you consume a source of carbohydrate, be it a potato, a banana or a bowl of cereal, your body breaks most of it down into sugars that it sends through your small intestine into your bloodstream. These sugars then travel throughout your body to where they are needed to fuel activity and physiological functions.
Simple vs. Complex Carbs
Fiber is the only type of carb that isn't broken down into sugar for fuel. In fact, your body can't process it at all, and it travels through your body mostly unchanged. Fiber slows digestion, thereby slowing the rate at which sugars are released into your bloodstream. Starchy foods, such as corn, brown rice and potatoes, are also considered complex carbs because they take longer for your body to metabolize. Simple carbs are lower in starch and fiber and have simpler structures; thus, the body is able to use them as a quick source of energy.
Plain sugar is the best source of instant energy. Honey, raw sugar, dextrose, maple syrup, jelly and other sources of sugar are also rich sources of instant energy. Refined carbohydrates such as white bread, white pasta and white rice have had most of their fiber removed during processing, and they are digested very quickly. They also provide nearly instant energy.
Fruits and dairy products provide simple carbs, but they also provide fiber, in the case of fruit, and protein, in the case of milk. This slows their digestion somewhat, but they're a healthier alternative to the simple carbs in sugary and refined foods.
Who Needs Quick Energy?
Most health-conscious people should avoid simple carbs from refined and sugary foods. While these foods provide instant energy, that energy spike is often followed by an energy crash that can leave you feeling tired, moody and hungry again soon after eating.
However, athletes engaged in long training sessions or endurance events may need these sources of quick energy; because they are so easily metabolized, they don't cause digestive discomfort during activity. While fruit and dairy might be suitable for some athletes to snack on during training or an event, others may find they cause digestive problems.
If you're not engaged in an endurance race or long training session, a piece of fruit or a glass of milk can provide a little boost before a workout. Your regular diet should be composed of complex carbs, lean proteins and healthy fats to provide long-lasting energy along with fiber, vitamins and minerals.