What happens inside the gut when a cat gets fat?

A study conducted at the University of Illinois College of Agriculture, Consumer and Environmental Sciences investigated what happens inside the gut i.e. the stomach and colon of a domestic cat when they eat too much and gain weight.

Fat cat. Image: MikeB (Canva) under license.

High level of feline obesity

The study researchers kicked off with this shocking bit of information: about 60% of cats in the US are overweight. Comment: I thought it was about 40% but the percentage keeps on going up. This extra weight can lead to serious health problems such as type II diabetes and joint problems and chronic inflammation.

11 cats participated in the study and here is another little bit of information which I also find shocking. These cats were fed a standard dry food diet. Dry cat food is known to be somewhat addictive because of the fatty spray they coat the pellets with. And this proved to be the case because they were allowed free access to this dry cat food. And during this time the researchers collected blood and faecal samples at regular intervals and they monitored the cats' activity levels.

Once the cats were allowed to free-feed they ate too much. I find that very strange because my cat doesn't do this and he is allowed a free feed. Perhaps the difference is that these cats were in some sort of research facility where they were allowed to move around but they might have become bored and boredom can lead to overfeeding. My cat is an indoor/outdoor cat and he spends quite a lot of his time outside being active.

To return to these cats. They put on weight fairly quickly. At the beginning of the study, they had average body weights. Using a cat version of human BMI, their BCS scores were 5.41 on a 9-point scale. After 18 weeks of overfeeding their BCS was 8.27. This meant that they were 30% overweight.

Gut microbiota composition

There were significant changes in gut microbiota composition. And the changes were surprising because the gut microbiota composition improved. There was an increase in a bacteria which has antimicrobial activity, which inhibits pathogens and stimulates the immune system. And likewise, there was a decrease in another bacteria which is linked to pro-inflammatory diseases. The former is called Bifidobacterium and the latter is called Collinsella.

The results were the opposite to what has been measured in overweight humans. In other words, when humans gain weight their gut microbiota becomes worse and less effective.

Transit times

This measures the amount of time the food, digested food and faeces remain in the body and travels through the body. The transit time was reduced and so was "digestive efficiency". When a cat eats less food, their stomach extracts more nutrients from the food and vice versa. This is because the food passes through the digestive system faster preventing an efficient extraction of nutrients.

Also course the cats pooped more which is to be expected! And finally, faecal pH decreased which meant that the poop became more acidic when they became fatter. pH measures the acidic and alkaline levels of a substance.

After this study they were put on a controlled restricted diet and they lost weight. The study impliedly found that if you feed dry cat food to a domestic cat you should restrict the diet. In other words, you should control the amount of food they have.

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P.S. please forgive the occasional typo. These articles are written at breakneck speed using Dragon Dictate. I have to prepare them in around 20 mins.

How do you define "cat obesity"?

When you think of the word "obesity" you think of very fat people or sometimes very fat cats (and I don't mean the human fat cat namely the greedy, alpha male smoking a cigar happy in the knowledge that they have ripped off people to make a large profit).

Just 15% above the normal

But it might surprise people that feline obesity refers to cats with a weight which is 15% above the ideal. That's not much more than 10% above the ideal. You might think that is acceptable. You might not even really notice it and I wouldn't blame you. That's because people, including me, tend to normalise weight gain. You gradually lose your bearings as to what is the correct weight both for yourself and for your companion animal. The problem creeps up on you almost invisibly sometimes.

So, a weight gain of 15% in your cat might not be noticed but a veterinarian would describe your cat as obese. And it might not surprise you that the most prevalent nutritional problem for domestic cats and dogs in Western Europe and the United States is obesity!

You may have heard about the obesity epidemic both in humans and cats and I suspect dogs as well. It affects between 10 and 20% of pet cats but that figure is probably out of date as it is constantly climbing. The figure relates to a book published in 2007. That's long enough ago for the obesity epidemic to become much worse.

Infographic

Overfeeding

The reason for cat obesity might be a medical condition and it should be ruled out before a weight loss program is started. However, in the vast majority of cases weight gain is associated with over-nutrition i.e. feeding too much. The cat is taking in an increased calorific intake or there is a reduced requirement for the body to burn up those calories. The infographic above mentions other issues.

To put it another way, the cat is either eating too much or not burning off enough calories or both. My mind immediately turns to the trend which I believe is taking place in America and in the UK to keep cats indoors full-time. This restricts activity. Cats become bored and they eat addictive foods for pleasure. This is a formula for obesity.

Health problems as a result of feline obesity

And the problems associated with obesity include:

• Respiratory difficulties
• decreased cardiac reserve
• insulin resistance and the development of diabetes
• poor response to infectious diseases
• fatty infiltration of the liver
• increased surgical risk due to increased risk of anaesthesia, fat necrosis, slow wound healing, technical difficulty in performing surgery and
• feline lower urinary tract disease.

A quite comprehensive list which comes from (verbatim) NUTRITION AND WELFARE in my book The Welfare of Cats Edited by Irene Rochlitz.

Slow weight loss

Veterinarians would provide a word of warning about reducing a cat's weight. It should not be done too fast as this can lead to hepatic lipidosis which itself is a serious disease which can, unless it is turned around, lead to the death of the cat.

Clearly, for an obese cat to lose weight requires self-discipline on the part of the cat's caregiver. It's probably wise to obtain veterinary support to encourage the owner to follow dietary recommendations. This may be crucial to success on occasions.

Eating less is more effective than exercising

In respect of people becoming obese and desiring to lose weight, my personal research indicates that the strongest way to lose weight is to reduce food intake compared to doing more exercise. The latter will certainly help but the former will have a more dramatic effect and it should be a permanent change in diet for the lifetime of the person and the cat!