Diet for overweight, frequently constipated cat

Question

I have a neutered, male, DSH red tabby named Playdough. We adopted him when he was eight months old and he is now almost three and a half years old. Recently, he has had two bad bouts of constipation. We took him in and they cleared him out, but we obviously need to change his diet. The vet put him on Royal Canin Fiber Response dry and recommended a little water, pumpkin, and yogurt go into his food.

The other issue: Playdough now weighs somewhere between 15-16 lbs. This is our fault as owners. Playdough shares the house with us, two other cats, and a small dog. Our last adoption was a kitten, and we free fed her until she was one (three days ago), so Playdough got into her food often. He's been pudgy since becoming an adult, but now it is clearly out of control.

So we have two issues to address: the constipation and the obesity. I want to get him down (eventually) to 12 lbs. In addition to playing with him more, and keeping him from getting in any additional food sources, I roughly sketched out the following diet:

Two meals a day, with each meal being comprised of:

• 52 grams Royal Canin Fiber Response dry cat food = 138 calories
• 1/4 cup water = 0 calories
• 1/2 tbsp canned pumpkin = 3 calories
• 1/2 tsp plain, unsweetened yogurt = 9 calories

Total meal = 150 calories, twice a day for a daily intake of 300 calories.

This is the first time I've had to do more than follow the guidelines on the packaging, so I'm feeling a bit lost. Does this seem plausible?

Thanks!

Answer 1

In my experience 300 kcal would be too much for most cats to achieve significant weight loss. I find the feeding recommendations on most cat and dog foods overestimates their calorie needs.

---

The formal way to calculate calorie needs is the resting and maintenance energy requirements.

RER (resting energy requirement in kcal per day) = 70 × W^0.75

where W = weight in kilograms at ideal body weight.

MER (maintenance energy requirement) is a factor of RER based on growth stage, health status, obesity, activity, etc. A nice summary of MER is given on the Pet Nutrition Alliance website.

For weight loss, I use 0.8 × RER. If only mildly overweight you may be fine to use 1 × RER.

---

For your cat, assuming a target body weight of 12 lbs:

RER = 70 × 5.4^0.75 = 248 kcal per day

MER = 0.8 × 248 = 198 kcal per day

Therefore, to achieve weight loss, based on these calculations you should be feeding closer to 200 kcal per day. Most cats will not appreciate switching from 300 kcal per day to 200 kcal per day immediately, so I would gradually taper off until you get to the desired calories (perhaps over the course of a few weeks). Gradual weight loss is wanted (no more than 1 lb per month). Adult cats do have surprisingly low calorie needs, and sometimes we find that even feeding 200 kcal is not achieving weight loss if the cat is extremely sedentary, in which case we may need to adjust further. Just keep telling them it's for their own good!

---

I would add that it is unusual for young cats to get constipated. In these cases there is always a reason, and it may just be diet-related in Playdough's case. If there are recurrent bouts of constipation on the new diet then you will have to assess whether there is an underlying medical reason he is becoming dehydrated, motility issue in the colon, stressful situation causing him to avoid the litter box, or other reason why he is not defecating regularly.

Consider adding some wet food to his diet, if he will take it; the moisture content can be very helpful in constipation cases. I often recommend switching to a sole wet food diet if there are several bouts of constipation.

Answer 2

The average adult cat needs from 270-320 calories a day to stay healthy. Larger cats use more energy, so if you feed 300 calories per day your cat will slowly lose some weight.

You need to follow the diet and not give any treats and you will need everybody in your household to help your cat to lose weight.

It is best if you can split the meals you give your cat into 3-4 servings per day. This will help your cat stay hungry for a shorter time between meals, so your cat does not beg for food all the time.

Try to have a fixed routine for your cat where your cat plays first and then eats and finally sleeps.

Be sure your cat gets all the water he needs (a water fountain can make your cat drink more water); it is best to place the waterbowl away from the food bowl as cats in general will drink more water when it is away from the food.

Answer 3

Constipation and obesity is extremely common with kibble fed cats. The most important thing regarding constipation is moisture so all dry food should be stopped forever. That includes any dry prescription foods which may contain excess fiber that could actually make the problem worse. Take care of the constipation before it causes permanent damage to the colon. Feeding a proper species appropriate diet rich in moisture will take care of both problems. Transition to canned food for now. Come back for more info on proper diet once that is achieved as it could take months.