Any food stuff consumed after a meal will lead to uninvited weight gain, regardless of what you consume, be it a junk food or a healthy fruit. If you consume more calories than the required amount for your body, it will result in weight gain. If you consume your food and have a piece of fruit after that, the fruit will not be able to pass through the intestines. This chunk will make your stomach to bloat up and make you run to the restroom. This is because the fruit will combine with the other foods and produce a gas, which will make your stomach to bloat.