I promise today’s post will be the last on cats and water … for awhile at least.
Last week, I came to the conclusion that healthy cats are “smart” enough to figure out when they need to drink and will keep themselves well hydrated whether they eat dry or canned food. Note the word “healthy” though. Some disease states do benefit from greater caregiver intervention to a cat’s water intake.
One condition is unfortunately all too familiar to many cat owners — chronic kidney disease. When a cat’s kidneys stop functioning properly, large amounts of water are lost into the urine. Up to a point, cats can compensate by drinking more, but eventually water losses become significant enough that they need help getting as much water as possible into their little bodies. Recommendations include feeding a canned-only diet, having fresh water available at all times, and supplementing with subcutaneous fluid infusions whenever necessary.
Another feline disease that can improve with a canned-only diet may come as a surprise — obesity. Many cats that are overweight will lose weight when they eat canned food only. This appears to be true for several reasons. Canned foods are higher in protein and lower in carbohydrates in comparison to dry, and high protein diets help cats maintain their lean body mass while promoting the loss of fat. This isn’t all that’s going on, however. The increased water content of canned food is important too.
In an elegant study from 2011, researchers fed two groups of cats either a canned diet or a freeze-dried version of the canned diet that had an identical nutrient profile with the exception of its water content. Cats that ate the canned diet containing water took in many fewer calories and lost a significant amount of weight in comparison to those that ate the freeze-dried version of the food. These results occurred despite the fact that in preference tests, cats ate significantly more of the canned food than they did the freeze dried version.
The high water content of canned foods makes these products bulkier without adding calories. Cats can only take in so much volume of food per meal and the calories are diluted by the large amounts of water present. To produce a similar effect, I’ve heard dieticians recommend that people drink a large glass of water or sip soup before meals to reduce their total caloric intake. I don’t recommend mixing water into dry cat food in an attempt to mimic the results of this study, however. Canned foods are designed to provide all the nutrients a cat needs at the proper levels in the presence of large amounts of water. Adding water to dry food will dilute everything, not just the calories, and could potentially lead to nutrient deficiencies.
Dr. Jennifer Coates
Wei A, Fascetti AJ, Villaverde C, Wong RK, Ramsey JJ. Effect of water content in a canned food on voluntary food intake and body weight in cats. Am J Vet Res. 2011 Jul;72(7):918-23.