Now if you eat fruits all the time in general or one specific fruit, you will lose weight.  There is no way to not lose weight by doing that.  But there are specific foods that you can eat and specific fruits that you can eat to really optimize your weight loss without specifically sticking to fruits in general and only that.

First you can try bananas.  Bananas are extremely high in fiber, and they are also loaded with potassium, and 75% of a banana is made up of water.  So this all adds up to greater and improved results in general.  It also helps with electrolyte balance in general.

Second, grapefruit-grapefruit according to studies has been shown to help obese people lose weight with increased insulin levels to metabolize sugars.  It has been used in a diet of its own, and it is true it can help your weight loss efforts with regular use, if used correctly of course.

Third, try cantaloupe.  Cantaloupe can help you with few calories such as 60 calories per cup, and it is loaded with vitamins and minerals as well as other nutrients and antioxidants.  Now I personally prefer strawberries above any of these as well as kiwis.  But these are the ones with the highest ability to promote greater weight loss.