Too many simple carbohydrates (sugars) can definitely hamper weight loss, but it depends on your overall diet, not just the amount of fruit that you eat. Fruit is certainly healthier than many other foods out there, just try to stick with fruits that have a lower glycemic index or lower glycemic load score (ie. eat those that have more complex carbs, rather than simple carbs). Tropical fruits and melons tend to have higher simple sugar content (high glycemic index score), so try to eat fewer of these. Stick with those fruits with more complex sugars (lower glycemic index & glycemic load), such as apples, berries, avocado (limit your serving!), grapes, nectarines, citrus fruits, guava, peaches, plums, pears, rhubarb, and strawberries. Bananas fall somewhere in the middle, so just try not to have too many... maybe cut down to one per day at most. But like I said before, it depends on your overall diet, so a banana is preferable over chips or most other snacks!