What is the Obesity Paradox?

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What is the obesity paradox?

Fact Files:

by Cassie W hite Being overweight or obese is known to increase your risk of a range of serious diseases. Yet researchers are finding you're more likely to survive a chronic illness if you carry extra weight.

How being overw eight or obese affects your health Is your w eight a good measure of your health?

Is w eight loss surgery the answ er for diabetes?

The low -dow n on physical activity Are diet soft drinks a healthy choice?

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It's no secret Australians are getting heavier. More than 60 per cent of us are overw eight or obese, and OECD data suggests w hen it comes to our w eight w e're the fourth biggest nation in the w orld Being overw eight or obese is know n to increase your chances of developing serious illnesses such as type 2 diabetes, heart disease and cancer, and maintaining a healthy BMI (Body Mass Index) is one of the best w ays to prevent these health issues later in life.

But a grow ing body of research suggests some people w ho are classed as "obese" have a better chance of surviving the chronic diseases that obesity causes in the first place. This phenomenon has been labelled the "obesity paradox" and it has researchers puzzled.

Breaking down the BMI The BMI scale is used w orldw ide and is considered the best w ay to measure a person's body fat in relation to their height.

It's easy to determine by plugging your height and w eight into an online calculator and it w ill quickly let you know if you're carrying too much fat.

Category Very severely underw eight Severely underw eight Underw eight Normal (healthy w eight) Overw eight Obese class one (moderately) Obese class tw o (severely) Obese class three (very severely)

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BMI Range Less than 15 15-16 16-18.5 18.5-25 25-30 30-35 35-40 Over 40

But many experts, including Professor John Dixon, head of clinical obesity research at Baker IDI Heart and Diabetes Institute, w arn BMI isn't the most accurate w ay of telling if someone is a healthy w eight, because it w ill change depending on the person, their age and health issues.

"Optimal w eight for health, longevity and mortality isn't constant – and w hy should it be for all adults of any age and w ith any disease?" he says.

When bigger is better The evidence for the obesity paradox has found those w ho are overw eight or obese are more likely to survive renal failure, heart failure, diabetes and coronary heart disease, regardless of their age.

Furthermore, one recent US study found being overw eight or class-one obese can actually protect people from all causes of death.

But despite all the recent research into the obesity paradox, experts still don't really know w hy it occurs.

How ever, Dixon says, "it certainly is a very real thing". He argues it's easier to understand how older people in particular are protected by carrying extra w eight, especially those w ho suffer serious w asting diseases.

"It's been found that in people w ith all forms of cancer, the bigger they are, the better they do in treatment, because they have greater reserves of muscle and fat at a time w hen they are under stress," he explains.

For example, a new review by Deakin University, w hich looked at research carried out on 20,000 people over the age of 65, found those w ith a BMI betw een 23 and 33 actually live longer than people w ith a BMI in the low er end of the normal w eight category (betw een 18.5 and 23).

But w hat is harder to understand is w hy young people w ith low er BMIs have a smaller chance of surviving a sudden serious illness than those of a similar age w ho are obese, explains Joseph Proietto, professor of medicine at the University of Melbourne.

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"Let's say there's someone w ith a BMI of 19 w ho's fit and healthy and someone w ith a BMI of 34," he says.

"Each has a heart attack because they've inherited high cholesterol. W ho'll survive better? The evidence suggests the person w ith the BMI of 34 has a better chance."

Proietto says it could be because people w ho are obese are often already being treated for conditions such as high blood pressure and cholesterol.

People w hose w eight is not an issue on the other hand, probably aren't even aw are that they have some of these health problems, giving them a disadvantage if they suddenly fall ill.

Cleaning up the confusion The obesity paradox seems a huge contradiction to everything w e've been told about maintaining a healthy w eight. So it begs the question: "w hy bother?" w hen it comes to diet and exercise.

It also doesn't help that researchers can't explain w hy obese people seem to fare better in illness.

Until more research is done, they're really w orking on theories.

But Dixon stresses the obesity paradox is definitely not an invitation to throw healthy eating and exercise habits out the w indow . Preventing these diseases should alw ays be your priority and the best w ay to do that is by staying lean w hen you're young.

"People under the age of 40 w ho have no illness should really be trying to keep their w eight dow n, because there's no doubt that overw eight and obesity is associated w ith disease: diabetes, heart disease, heart failure," he says.

Up until middle age you should attempt to stay w ithin a BMI of 20-25 and lead a healthy, active lifestyle, Proietto says.

"But as you get older, you shouldn't fuss too much if you gain a little w eight, because it's w hen you're older that you're going to have a stroke or heart attack or surgery," he says.

"How ever, this doesn't apply if you're massively obese. Morbid obesity shortens your life, w ithout a doubt."

Once you reach middle age, he recommends focusing on keeping fit and eating highly nutritious foods, rather than losing w eight.

"If you stay fit, you're at least minimising your risk of having cardiovascular problems," he explains.

But if you suffer from, say, diabetes and you're over 50, you're much better off asking yourself, "W hat's the ideal w eight for me?" and seeing your doctor for advice.

"We're not suggesting severely obese people shouldn't try to improve their diet and lifestyle, and try to lose w eight," Dixon says.

"If they can take off just three per cent of body w eight, that has measurable benefits on their health.

"But w e can't ever expect people over the age of 60, for instance, to try to achieve a 'normal w eight' range, w hich may not be good for healthy ageing.

"I think the real concept here is that the normal w eight range isn't necessarily the healthy w eight range for a given individual."

Published 14/04/2014

More info Is your w eight a good measure of your health? - ABC Health & Wellbeing How being overw eight and obese affects your health - ABC Health & Wellbeing W hat is a healthy w eight? - ABC Health & Wellbeing

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Paul :

14 Apr 2014 5:48:19pm

I think the w eight paradox occurs because of marriage. Married couples gain w eight and live longer.

It's probably that simple.

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Zeta :

16 Apr 2014 12:41:52pm

stupid comment, not helpful.

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Ben Heslop :

17 Apr 2014 2:43:02pm

It might be a legitmate confounder!

W ho the hell are you Zeta to dismiss it? W here's your linked research?

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