How to choose a dog food for weight loss

The short answer

1. Check the calories per cup. It is printed on the bag. Lower means a bigger portion for the same calories.
2. Look for high protein and high fibre. They help a dog feel full and keep muscle.
3. Choose a food made for weight loss if you need to cut a lot. It keeps vitamins and minerals high in a small portion.
4. Do not trust the feeding guide. It is often too much for weight loss.
5. Ask about a vet diet if your dog has a lot to lose or a health problem.

Do you need a special food at all?

Not always. If your dog has only a little to lose, feeding a bit less of the normal food can work.

For bigger cuts, a weight-loss food is safer. Normal food is made to be fed in normal amounts. In a 2012 study, researchers checked five normal dog foods fed in smaller weight-loss amounts. As the portion got smaller, every food fell below the recommended level of at least one nutrient. A 2013 follow-up fed dogs a food made for weight loss. The dogs lost weight and stayed healthy, with no signs of missing nutrients.

1. Check the calories per cup

Every bag sold in the US must show the calories, usually as "kcal per cup" and "kcal per kg". This one number tells you more than the front of the bag.

Weight-loss foods are not all alike. A 2010 study at Tufts University looked at dog foods sold for weight loss. The dry foods had from 217 to 440 calories per cup. So one "diet" food can have twice the calories of another.

Lower calories per cup means your dog gets a fuller bowl for the same calories. That makes the diet easier for both of you.

2. Know what the label words mean

These rules come from the model rules of AAFCO, which most US states use for pet food. UK and EU labels follow different rules, so check the calories there too.

3. Look for high protein and high fibre

Protein helps a dog keep muscle while losing fat. Fibre adds bulk, so the meal fills the stomach more.

In a 2010 study of obese pet dogs, dogs on a food high in both protein and fibre lost more weight and more body fat than dogs on a high-protein food with less fibre. Many weight-loss foods use this mix.

4. Do not trust the feeding guide

The amounts on the bag are a starting point for an average dog. They are often too high for weight loss. In the 2010 Tufts study, most dogs would not lose weight if owners fed by the bag.

Feed for the weight your dog should be, not the weight it is now. The dog food calculator works out cups from the calories on your bag.

5. When a vet diet makes sense

Vet diets, also called prescription or therapeutic diets, are sold through your vet. They are made for large calorie cuts. They pack more protein, vitamins and minerals into each calorie than most shop foods.

Ask your vet about one if:

• your dog has 20% or more to lose,
• a shop food has not worked after a few months,
• your dog has another health problem, such as diabetes or joint pain.

They cost more than most shop foods. Your vet can tell you if your dog needs one.

Dry, wet or fresh food?

All can work. The calories per day matter more than the type. Wet and fresh foods have more water, so a meal looks bigger for the same calories. Some dogs feel fuller this way. Dry food is cheaper and easy to weigh. You can also mix them. Just count both in the day's amount.

How to switch to a new food

1. Mix a little new food into the old food. Add more each day, over about a week.
2. Work out the new amount. The calories per cup are almost never the same, so the old scoop size will be wrong.
3. Weigh your dog every week or two. A safe pace is about 1% of body weight a week.

Our 7-step weight-loss plan covers the rest, from treats to weigh-ins.

After the weight is off

Many dogs gain the weight back. In a follow-up study, about half of dogs that lost weight regained it. Dogs that stayed on a weight-control food regained less. So keep the food, and raise the amount only a little.