Knowing which veggies and fruits have more sugar than others will guide you...
Greens are the least sugary (fattening) of the veggies... (They are the key to a successful juice fast)
Carrots and beet etc., are the most fattening of the veggies because they have more sugar.
Fruits are more fattening than veggies, again, because of the sugar content.
Citrus is the least fattening of the fruits.
Green Granny Smith apples are the least fattening of the apples because they contain less sugar.
Here's a link that offers lots of articles, tips and tricks including recipes and the properties of various fruits and veggies and how they benefit the body. http://curezone.com/blogs/m.asp?f=573&i=78