The less type of foods we consume during a meal, the better and easier the digestion process is. Each food, including the ones from the same group, is digested by a different set of ferments.
People don't put on weight because they tend to binge on main meals, but because they eat when not really feeling hungry. Whenever hanging out with friends, most of the people order a beverage, such as juices, or desserts now and then, and do not really take that as a calorie intake, so they end up getting fatter.
Don't combine sweet fruits with protein-loaded foods since the assimilation of the latter happens in an acidic environment. Besides, when combined with bananas, for instance, it will take a toll on the digestive process.
I do advise you to have fruits for breakfast and consume them alone. If, however, you fail at satiating the hunger throughout the day and feel extremely hunger in the evening, you can treat yourself to a few slices of fruit, but do not overdo it. Sticking to that rule is quite hard, but leads to a better digestion.