The amount of fruit sugar (fructose) varies from fruit to fruit and may have some adverse metabolic effects, such as a decrease in fat burning. However, the benefits of fruit (low in caloies, high in fiber, water and nutrient content) outweigh the adverse effects on most people. But if you are having trouble losing weight and can't figure out why, limiting your fruit intake may help.

Firstly, it's important to differentiate between naturally occuring sugar and added sugar. Most experts recommend a minimum of 130 grams of total carbs per day, including fruits and whole grains. In general, no more than 10 percent of your calories should come from added sugars found in products like sweetened beverages, sauces and dressings. While fruit does not contain added sugars, if you are trying to lose weight, limiting your sugar intake is key, and this means no more than two servings of fruit per day. That's a medium banana and a half cup (1 dl) of berries. But if you're active and do not have excess belly fat, you can go up to three or four servings a day.

Besides sugar, the total number of calories also counts. Fruit contains almost three times the calories per serving as most nonstarchy vegetables, so don't consider fruit a "free food" (where the calories don't matter), as you may unknowingly consume up to 250 extra calories per day. This may prevent you from losing one pound of fat every two weeks. Avoid dried fruit, fruit cups and fruit juice, since they're higher in calories and typically lower in fiber than fresh or frozen fruit. For effective weight loss, stick with fresh or frozen fruit only. And remember, while natural sugar is healthier than refined sugar or high-fructose corn syrup, it still contains the same number of calories per serving (four per gram).

Some fruit pack hidden, weight-loss and fat-burning potential. Add these to salads, stir into yogurt, whirl into a smoothie or eat out of hand.