The Dukan diet is a very popular way of slimming down, especially for those who live in France. On this particular fad diet, tomatoes are allowed, though in moderation. You will find that with a lot of the recipes which are given to people who are on this diet, tomatoes are often included in small amounts.
If you enjoy eating tomatoes on a regular basis, you should have no issues with having to cut them out completely, although it is important to introduce different foods into the meals you eat. Tomatoes can provide a lot of nutritional value to just about anyone, including those who follow the Dukan diet.