Fructose
Another monosaccharide, you'll find fructose in fruit, fruit juice, honey and vegetables. It differs from glucose in that the liver breaks it down before it moves through your blood and then to your muscles. Another drawback: Free radicals and triglycerides (a type of fat), form as by-products as your liver processes fructose. So getting an excess amount can directly contribute to weight gain. To avoid this, try to stick to two cups of fruit a day, limit juice and don't overdo it on the honey toppings. A small banana or handful of raisins can go a long way pre-cardio sesh.