Fruit should be eaten on its own and on an empty stomach. (This has nothing to do with losing weight.)
Fruit that is trapped in the stomach can ferment and cause bloating and discomfort. When you eat fruit on an empty stomach it can travel straight through the stomach to be digested in the large intestine.
So, eat fruit for breakfast, 15 minutes before a meal or 3 hours after a meal.
The exceptions to this guidance are cooked fruits (because they will not ferment) and fruits that contain so little sugar that they are unlikely to ferment such as strawberries, raspberries, blackberries, redcurrants and bilberries.