Find out exactly how many calories your pet needs.

Find out exactly how many calories your pet needs.

Pet foods can vary a lot in calories. There are minimal government restrictions on pet foods labeled as light, lite or low-calorie. Foods labeled "reduced calorie," "healthy weight" or "obese prone" are unregulated with respect to calories. As a result, pet foods marketed for weight loss can range from 200 to 500 calories per cup (300 calories or less per cup is optimal for weight loss). Adding to the confusion, feeding guidelines on pet food labels vary and usually overestimate how much an overweight animal needs. No wonder helping pets lose weight is challenging!

Your vet is the best source to determine your cat or dog's caloric needs, but with a little math, you can calculate the number yourself.

DOG: Calories required per day = 70 x (pet's weight in pounds x 0.45) 0.75

CAT: Calories required per day = 0.8 x [70 x (pet's weight in pounds x 0.45) 0.75]

By 2015, all pet foods will be required to have calories on the label. Until then, if it's not on the label, call the company. Usually calorie amounts are written as kcal per cup or can. Now, more math: Divide your pet's needed number of calories per day by the number of kcals per cup or can, and you have the daily amount of that food (and that food alone) that you should be feeding.

Just like with people, caloric needs can vary greatly between animals, so you might need to adjust that amount to achieve a healthy rate of weight loss, which is generally considered to be around 1-2 percent of a pet's body weight per week.

As pets lose weight, the number of calories they need also drops, so it's worth recalculating your pet's needs every couple of months. And while it may seem like an easier option, simply cutting down on your pet's current regular food reduces not just calories, but also essential nutrients.

Bottom line: Go by the numbers, not the name when choosing a food for your overweight pet and pick one lower in calories than what you're currently feeding to ensure your pet get all the essential nutrients.