over weight dog

Question
I have been feeding my dog a small tin of tuna in the morning, boiled chicken in the afternoon, and another small tuna at night so she can lose weight is that ok, only started this week.

Answer
Do you have any idea how much protein, vitamins, minerals, fat, etc. is in that diet and how it compared to a dog's needs?  She would be much better off eating a standard dog chow or perhaps a light formula.  Your dog definitely should be narrower at the waist than the hips and chest. You should be able to easily feel the ribs, but not see them. Each dog is different. Standard recommendations are a good place to start, but each dog must have its food and exercise adjusted to its individual needs. Here is a link to a good illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx

The AVMA cautions against homemade diets, http://www.avma.org/press/releases/070404_homemade_diets.asp