DEAR DR. FOX: I have two Cavaliers -- one is 6, and one is 17 months. It is much easier to have them on the same food but if not possible, I can handle two different foods. Currently, they are on the same food, Iams, but my 6-year-old has gained two pounds, and the vet tells me that it is because Iams is a fatty food. I am trying to find a healthy, yet affordable food that they could both eat. Should my 17-month-old be on adult food now? When are dogs considered adults in the dog-food world? Any suggestions?

-- B.P., Washington, D.C.

DEAR B.P.: Your two dogs need to get on a more healthful diet. The high-fat and high-protein puppy food should not be given to most breeds after six to eight months of age. And for some breeds, especially Labrador pups, such a diet is actually harmful. Studies indicate this diet can make developing hip dysplasia significantly worse, and lead to weight-control problems later in life.

Many factors could be making your older dog gain weight, become less active and begin to decline in health. Aside from the often-dubious ingredients in processed and animal junk foods, and the nutrient deficiencies and pesticide contamination of conventionally grown pet foods, we have environmental chemicals all around us. Many of these are called endocrine disruptors, and they can play a role in both dogs' and humans' weight problems. The Canadian province of Ontario just banned lawn-and-garden pesticides -- an important step for pets, wildlife and us!

Then there's the bisphenols that line food cans and fire-retardant bromides in aerosol dust that can affect the thyroid and immune system. There are so many endocrine disruptors everywhere, and many have been found in blood samples of cats and dogs living in what we would call regular homes. I do not mean to be an alarmist, but these multiple health issues call for much greater vigilance over the use of household cleaners, detergents, room deodorizers, as well as what we eat and feed to our pets who share the same environment.

Your dogs would do well on the diet I have developed, but reduce the grain content by half. It is published on my Web site at www.doctormwfox.org. It is important to transition dogs over a few days when going onto a new diet, and to weigh them weekly to monitor weight gain or loss.

Both dogs should have regular outdoor walks and lots of physical activity, ideally off-leash where permitted and safe.

DEAR DR. FOX: We have a 5-year-old male cat that started having trouble going to the bathroom about a year ago. His constipation became very serious.

The vet prescribed Cisapride and Lactulose twice a day, as well as two Dulcolax pills every day. It seemed to work for a while, but we now have to take him to the vet about once a month to be sedated and manually cleaned out. Are there any other treatments/medications that might be more effective than repeated enemas? He is fed both dry and canned cat foods. This cat lives with other cats, is physically active, and is on the aggressive side with other cats.

-- T. -- K.B., Minneapolis, Minn.

DEAR T. -- K.B.: This is a complex condition to treat. And it is all too common in the feline population today.

Some cats do better on a home-prepared diet, even mainly raw food ingredients when gradually transitioned, plus probiotics and digestive enzymes. Others do better when given some bulk laxative mixed into their food -- like a teaspoon of chopped wheat grass or psyllium husks.

I would like to learn from other readers who have had cats with this condition. One of my theories is lack of stimulation and physical activity, but your cat seems to indicate otherwise. Is it more prevalent in cats that live without the stimulation of other cats? Is it more common in easygoing, passive felines and in those fed highly processed manufactured cat foods rather than in cats fed whole, unprocessed and even raw foods?

Send your questions to Dr. Fox in care of this newspaper. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.