What the extra weight actually costs

The Labrador study

Purina ran a lifetime study on forty-eight Labradors from seven litters, paired by sex and weight, and raised in the same conditions. One of each pair was fed a normal amount; the other was fed twenty-five per cent less.

The lean-fed dogs lived a median of 13 years against 11.2 — nearly two extra years from the feeding alone.

They also developed osteoarthritis later and less severely, and needed treatment for it much later in life.

It is the clearest evidence in companion animal medicine that a decision an owner makes every day, with no cost and no equipment, changes how long the animal lives and how comfortable it is while doing so.

Learning to see it

The hard part is that an overweight animal looks normal once you are used to it, and a correctly lean one often looks thin to visitors.

Use your hands rather than your eyes. Run flat palms along the ribcage: you should feel the ribs easily, with a thin covering, like the back of your knuckles rather than the back of your hand. If you have to press to find them, the animal is overweight.

Look down from above. There should be a visible waist behind the ribs.

Look from the side. The belly should tuck up toward the hind legs rather than running level.

Vets use a nine-point body condition score and will happily show you where your animal sits. Ask at the next visit — it takes a minute and recalibrates your eye permanently.

One breed exception worth knowing: sighthounds are meant to show ribs, hips and spine. An Azawakh or a galgo at a correct weight looks alarming to anyone unfamiliar with them.

How it happens

Almost always slowly, and almost always through things that do not feel like meals.

Treats are the usual culprit. In a ten-kilogram dog, a single large biscuit can be a tenth of the day's calories. The working rule is that treats should be no more than ten per cent of intake, and that everything counts — training rewards, chews, the corner of toast, the last of the yoghurt.

Guideline amounts on packaging are generous and are calculated for an average active animal. Feed for the weight the animal should be, not the weight it is.

Use kitchen scales rather than a scoop. Cup measures of dry food vary by a large margin depending on how they are filled.

Neutering lowers energy requirements by a meaningful amount, and the food usually does not change. That is why so many animals gain in the six months afterwards.

And free-feeding — a bowl always full — makes it impossible to notice a change in appetite, which is one of the most useful early signs of illness.

What it causes

Osteoarthritis, earlier and worse, in every joint the animal has.

Diabetes mellitus, particularly in cats, where obesity is the largest modifiable risk factor. Burmese and Burmese-derived breeds start from a higher baseline risk.

Breathing difficulty, and disproportionately so in flat-faced breeds, where fat around the neck and chest compounds an airway that was already compromised.

Higher anaesthetic risk, more difficult surgery, and worse wound healing.

In cats, an increased risk of hepatic lipidosis if they then stop eating. In rabbits and guinea pigs, an inability to reach and eat their caecotrophs and to groom their own rear end, which leads directly to soiling and, in warm weather, to flystrike.

And reduced quality of life in the plainest sense: less play, less interest, less of the animal you got.

Taking it off

Slowly, and with a vet involved. A sensible target is one to two per cent of body weight a week.

Never crash-diet a cat. A cat that stops eating, or loses weight rapidly, can develop hepatic lipidosis — the liver is overwhelmed by mobilised fat — and it is life-threatening. Feline weight loss should always be supervised.

Weigh the food. Weigh the animal, on the same scales, every couple of weeks, and write it down; the number is what tells you whether anything is working.

Replace treats rather than removing them. Green beans, carrot, a portion of the daily ration kept back in a pocket — the animal is counting events, not calories.

Use puzzle feeders and scatter feeding to make a smaller meal last longer.

And rule out the medical causes first. Hypothyroidism in dogs and Cushing's disease both cause weight gain, and no amount of dieting fixes either.