This is an excerpt from Bodybuilding by Peter Fitschen & Cliff Wilson.
FAQ: Should I be concerned about sugar intake during contest prep?
There is no evidence that sugar consumption affects fat loss if macronutrient requirements are met each day. Diets high in fructose (the sugar found in fruit) have not been shown to affect weight loss compared to low-fructose diets. Similarly, diets high in dairy (lactose) have not been shown to inhibit fat loss.
However, foods high in added sugars are typically lower volume and higher calorie. Consuming a lot of calories from added sugar may lead to increased hunger due to a low food volume. In addition, many foods high in added sugars are micronutrient poor; therefore, we recommend consuming at least 80 to 90 percent of food from nutrient-dense foods to meet micronutrient needs.
For competitors with a low carbohydrate intake (i.e., 100-150 g per day or less), it may be advisable to limit fruit to one serving a day. This has nothing to do with fruit's effect on fat loss; however, fructose from fruit is primarily stored in the liver as glycogen, whereas glucose can be made into muscle glycogen. A diet high in fructose with a low carbohydrate intake may lead to further muscle glycogen depletion and a reduced performance in the gym. Therefore, it may be in your best interest to limit fruit intake to a certain extent if your carbohydrate intake is low.