What class of biological molecules does sugar belong to and what are the most common types of sugars in our diet?

1. What class of biological molecules does sugar belong to and what are the most common types of sugars in our diet?
2. What are the main sources of sugars in your diet?
3. How do sugar molecules provide us with energy? What other molecules (besides sugars) serve as a source of energy for our bodies?
4. In terms of sugar consumption, what are potential dangers of processed foods and low-fat foods?
5. How do we know how much energy different types of food have? Why food labels list everything per 2000 calorie diet?
6. How do we know how much food do we need to eat?