The sugar contained in fruit is called fructose. Many people have come to believe that fructose is bad for you and will promote fat gain. This is simply not true. Fructose metabolizes differently than other types of sugar but it is still a great choice for carbohydrates. Fructose will restore liver glycogen levels quickly and muscle glycogen stores slowly. Although fructose is technically a sugar it does not cause a spike in blood sugar like many other sugars. This makes fruit and excellent choice for daily consumption.
This may explain why the fat-burning effects of eating more protein were confirmed in a study published in the American Journal of Physiology. One group was fed a high-protein diet (just over 1 gram per pound of body weight per day) while the second group consumed an amount closer to the lower recommendation of the RDA (recommended dietary allowance). The group eating the higher-protein diet burned the most fat.