If you’re trying to lose weight, it will help to eat less animal products: meats, poultry, dairy. Animal products not only contain a higher amount of fat, they also carry the kind of fat that’s not so good for your arteries and heart: saturated fat.
On my "Joy of Weight Loss Plan" (and on the USDA Food Pyramid, too) I recommend eating only two servings of meat, and two of dairy per day. How much is a serving? About the size of a deck of playing cards for meats (or 2-3 ounces). For dairy, a serving is one cup of milk or yogurt, 1/2 cup cottage cheese, or two ounces processed cheese (two slices) or 1.5 ounces natural cheese (a modest-sized chunk).
If you want to be a vegetarian, OK, just make sure to get your protein every day from nuts and beans, combining them with a grain (carbohydrate, such as rice, pasta or bread) to be assured of plenty of all amino acids you need.
You should have some dairy, daily, for the calcium, or take a calcium-enriched vitamin. Consult with your doctor.
Eating less animals and animal products will make for less of you – a human animal!