Back to basics
Carbohydrates are your body’s go-to source of energy, and they’re digested quickly. Glucose — the most basic unit of a carbohydrate — is the only type of carb your cells can use directly to make energy. But the carbs we eat come in three forms — sugars, starches and fiber — and when it comes to weight loss, these three are not equal. [What Are Carbohydrates?]
Sugars (found in fruit, vegetables and dairy) and starches (found in grains, vegetables and beans) ultimately suffer the same fate: They’re broken down into glucose and are used by the body for energy. But your body can use only so much energy at once, so not all of the glucose you eat is immediately used for fuel. Some of the extra glucose can be stored in your liver or muscles and be used later.
As for the rest? It gets converted to fat.
The difference between sugars and starches — which are sometimes referred to as “simple” and “complex” carbohydrates, respectively — is the complexity of their structure. Sugarscontain only one or two molecules, so it’s very easy for the body to digest sugars and absorb them into the blood. Starches, in contrast, contain many simple carbohydrate molecules linked together. Because of their size and complexity, starches take longer to be digested into single molecules.
Fiber is an entirely different ball game. Fiber is found alongside sugars and starches in fruits, vegetables, whole grains and legumes. Like starch, it’s a complex carbohydrate, meaning it contains many carbohydrate molecules linked together. However, your body can’t digest fiber, so this carbohydrate doesn’t get absorbed by the gut. It never enters the bloodstream, and it is never broken down for energy. The stuff passes through your body relatively untouched.