Carbohydrates are the body's primary source of energy, providing 45-65% of daily calories. Carbohydrates are digested into glucose which is transported through the bloodstream and converted into energy in cells to power bodily functions. Carbohydrates come in two forms - simple sugars that provide fast energy and complex starches that release energy more slowly and sustainably over time. Adults should aim to consume 200-300 grams of carbohydrates daily through a mix of starches and sugars.