As with any food, eating too much fruit can lead to weight gain. Due to the low calorie content of most fruits, however, you would have to eat a very high volume to gain weight -- especially compared to more calorie-dense fare such as cheese, meat, nuts and pastries. Some fruits, such as avocados and olives, contain more calories per ounce than apples, peaches, berries and other common fruits, so moderation is key with these choices when you're watching your weight.
Fruit and Weight
You gain weight when you eat more calories than your body burns for energy, causing it to store the excess as fat. One pound of fat contains about 3,500 calories; so by eating 3,500 more calories than you burn, you gain a pound. It usually takes a lot of fruit to get close to this number. For example, one medium orange contains about 80 calories, so you'd need to eat about 44 oranges on top of your normal weight-maintenance diet to gain 1 pound. A whole avocado, however, contains about 250 calories, so 14 of these on top of a normal diet would lead to an added pound.