Yes, carbohydrates are used first by your body for fuel, and yes, sugar is technically a carbohydrate. But it's a highly refined and processed one; not exactly the type your body needs to function.
"Sugar is used for metabolism," says obesity medicine specialist Dr. Nitin Kumar of the Bariatric Endoscopy Institute. "However, that does not mean that you need to consume a constant stream of sugar to continue powering your brain, muscles, and natural processes. Your body can convert other macronutrients (fat or protein) into energy."
A calorie is a calorie is a calorie
"With only 15 calories per teaspoon, sugar is no more fattening than any other 15 calories."
This has been sugar's main line of defense in recent years: Maintaining a healthy weight is all about calories in and calories out. If that were true, you could replace your daily healthy breakfast of Greek yogurt and berries with a donut and be none the wiser.
Sadly, not all calories are created equal.
"Sugar calories are not the same as fat calories, and not even the same as other types of sugar," Dr. Kumar says. "Sugar, particularly fructose, may stimulate insulin resistance, which can lead to increased blood sugar and more abdominal fat."