From an early age, we're encouraged to eat lots of fruit and vegetables, but there are many fruits that are so loaded with sugar that they can be considered to be nature's candies.
While a piece of fruit is usually a smarter option than reaching for a candy or a cookie, neither of which provide useful micronutrients, vegetables are usually a better choice.
When you're trying to lose weight, it's very important to be aware of the sugars in the foods you eat. The website SugarStacks provides many excellent visual comparisons that might surprise you. It includes numerous different types of food that surround us every day (not only fruits and vegetables) and stacks up the number of equivalent sugar cubes.
Next, head over to Mark Sisson's Daily Apple where he provides some great visuals that show the effect of your daily carbohydrate intake on your weight.
You don't need to count calories to lose weight, but you do need to radically restrict your carbohydrate intake. Knowing what is in the foods you eat is an essential part of this process.