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Appearance vs. reality: the perfectly healthy obese

No one can claim to be unaware of the risks of obesity in this day and age. Almost every day there are discussions in the media about the risks of carrying excess fat. But research shows the link between…

Evidence suggests that up to 30% of people who are obese are perfectly healthy. Rudd Centre for Food Policy

No one can claim to be unaware of the risks of obesity in this day and age. Almost every day there are discussions in the media about the risks of carrying excess fat. But research shows the link between obesity and ill-health is not as simple as it’s often made out to be.

Obesity is all over the media – newspaper and magazine articles talk about high blood pressure, diabetes, heart disease and more unusual illnesses linked to obesity, such as sleep apnoea; there are suggested diets and exercise plans to help reduce fat at every turn and; popular, humiliating television shows enforce strict weight-loss regimens on the morbidly obese while providing entertainment.

But while research shows obese people often have metabolic conditions such as high blood pressure, diabetes and cardiovascular disease, this is not the whole picture. What’s rarely, if ever, mentioned in the popular press (although it’s receiving growing interest in scientific circles) is the phenomenon of the metabolically healthy obese.

In most obese people, we can find evidence of metabolic abnormalities that result from the excess fat they carry. We can measure that these people need more of a hormone called insulin from their pancreas when they eat, to help burn up glucose in their cells. We call this phenomenon “insulin resistance”. It’s insulin resistance that eventually causes obesity-related complications such as high blood pressure, high blood fat levels, diabetes and heart disease.

There has, of course, always been something of a paradox around fatness and the Metropolitan Life Insurance Tables survival curves, which show how long people live at different body weights. In the Life Insurance Tables, being overweight in itself is not actually a risk for early death – certainly not when compared with being underweight. This may, in part, relate to the fact that serious illnesses are often heralded by long-term insidious weight loss, particularly as we get older. It’s only at obese levels of weight that mortality is clearly higher.

Up to ⅔ of adults are now overweight or obese – why is obesity so common? Evolution gave many of us particularly good “thrifty” genes that help us to eat fast, store fat easily and not waste energy in futile exercise. Theses genes were very important in times of famine because they ensured people had enough energy (or fat) stored to raise their young and still be healthy.

Unfortunately, the environment has recently been giving us too many opportunities to grow that fat store, and, for some, the consequences of excess fat are – as we hear so often – dangerous for health.

But while being in the obese range (Body Mass Index or BMI – weight in kilogram² divided by height in centimetres – of 30 and over) increases mortality, there are some people in that category who are somehow protected from the risks of metabolic harm. The most fascinating part of this is evidence suggests that up to a ⅓ of people who are obese are metabolically healthy. But there’s not yet universal agreement on the percentage of people who are in this group so research to identify them is important.

Of course, being active and exercising even if your weight remains high is better than not being active at all. But exercise doesn’t appear to explain why some obese people are healthy, as many obese people are quite sedentary.

For metabolically healthy obese people, a strong lifelong focus on losing weight may be misplaced if there are no other disease risks attributed to their weight. But it’s also important to research whether these people are, in fact, permanently protected from insulin resistance and its metabolic consequences, particularly if they gain more weight as they age.

This is of great important because if some people are really protected from obesity-related health risks in the long term, obesity treatment could benefit from understanding how that protection works.

Our research group at the Garvan Institute studied the short-term effect of weight gain by overfeeding healthy individuals (some of whom were overweight or obese) for one month. We studied them before and after they ate about 1,000 kJ extra every day – some of it in high-fat snacks. On average, there was a deterioration in our subjects' insulin sensitivity and they gained extra liver fat as they gained weight.

But responses varied and some people remained insulin sensitive despite their weight gain. We are now planning a longer study to follow up subjects we tested five years ago to see what has happened to their metabolism as they gained (or possibly lost) weight over time.

If we can find out what protects some people from the common metabolic consequences of obesity such as high blood pressure, diabetes and heart disease, we’ll be better able to treat obese people with these problems. This fascinating puzzle will take time to resolve but what we do know is that not all obesity is unhealthy.

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22 Comments sorted by

  1. Amy Dobek

    MSW Student

    Thank you SO MUCH for being willing to open up a dialogue about such a polarizing subject and being open to seeing the actual facts of the matter as opposed to just going along with conventional wisdom in the face of opposing evidence. You have earned my respect and my gratitude.

  2. Peter Fox

    Medical doctor

    "many obese people are quite sedentary". Thank you Lesley, the last few days on The Conversation has seen many people deny this logical correlation and ascribe it to 'bad genetics'.

    Whilst the concept of the "metabolically healthy obese" remains a hypothesis, and an interesting area of further research, it is important that the public health message is not muddied. It would be a disaster for an obese person in the queue at their favourite fried chicken chain to justify their choice with "but I'm one of the healthy obese". It would be interesting to see if this hypothesis plays out in malignancy, since obesity-related cancers (breast, colon, oesophagus, kidney, etc) are amongst the fastest growing.

    1. Frances Lockie

      Policy officer

      In reply to Peter Fox

      "Thank you Lesley, the last few days on The Conversation has seen many people deny this logical correlation and ascribe it to 'bad genetics'."

      We haven't denied that it exists, we argue that obesity does not automatically equate to poor health. Just as this article argues.

  3. Tony Linde

    retired geek, now arty-farty type

    I know that the science may show that some obese people may be healthy (though I'll be surprised if it is anywhere near as high as 1/3rd) but it worries me that this may translate into the idea that obesity is ok for some. Obesity means eating more calories than necessary which, ultimately, means either that we are overproducing in order to make those calories available or we are consuming calories at the expense of others who are missing out. And that seems ethically wrong. No?

  4. David Poynter

    Medical Scientist

    Sure, obese people can be healthy - for a little while.

  5. Garry Egger

    Professor of Health and Human Sciences at Southern Cross University

    You are spot on Lesley - although like much ingrained science this is heresy to some. To further support your view, there are the 'lean-but metabolically obese' (about 1 in 4) who have all the symptoms the obese should have, but who are lean. Does this mean that obesity is a 'canary in the mine shaft', signally bigger problems in the environment? Is it the things that cause obesity (diet, inactivity, stress, environmental chemicals etc) rather than obesity per se, which is unhealthy. As someone who has made a living out of obesity (cf. 'GutBusters'), I'm now 'ethically challenged' by such a simplistic view of the problem - we need to look deeper into the 'cause of the cause'.

  6. Geoff Ahern

    Interested Reader

    I'm glad we're talking about this. It's not fair if you are overweight that people automatically assume you're also a glutton. I'm "geneticially wired" if you like, to be thin. But, I do watch what I eat. I always have. I do eat in moderation and I do exercise moderately.

    People often ask me why and make comments like, "Why would you worry about getting fat?" and, "As if you'd have a heart attack."

    Well, I'm not worried about getting fat. I like to be relatively fit and healthy, I actually…

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    1. Diann Arcana Johns

      logged in via Facebook

      In reply to Geoff Ahern

      You have to love yourself first, before you can have a healthy lifestyle. You have to care enough about yourself to make good choices. The contestants on those shows are humiliated and shamed into change. How many have gained it all back? When you hate yourself becoming thin isn't going to erase your self-loathing.
      If you're obese and you're eating healthy food and exercising then that's better than not doing that right? I guess it's not good enough until you're holding up a big pair of pants in front of you so people can go ooooohhhh amazing transformation!!
      I really don't get this entire resistance to fat people loving themselves and taking care of themselves.

  7. Paul Rogers

    logged in via Twitter

    As Peter Fox has suggested, how does the 'healthy obese' hypothesis play out for cancer? And there are other health consequences of obesity such as knee osteoarthritis, asthma and respiratory disease, to name a few. Being 'healthy' is not only defined by cardiovascular and insulin/glucose normality.

    Like Tony Linde, I would be surprised if one third of BMI > 30 (and assessed for obesity with waist and waist/hip criteria), are metabolically 'normal'.

  8. Sam Chafe

    Retired scientist

    I'm a bit on the portly side, and I am pleased to relate that some of my best friends are, well, fat. But there seems to be no end to the extent some people are prepared to go to supposedly protect us from ourselves, often when the claims of harm are dubious. Hence, the obesity zealots. I remember hearing on the ABC a few years ago the results of a study which found no increase in obesity, either in children or the general population. I'm not sure if that still applies, but coupled with the facts that fat people are supposedly healthier than normal and underweight people, at least a few years ago (Michel Gard, The Age, 3/11/05), and are also happier, less depressed and less likely to commit suicide (Zoe Williams, The Age, 3/1/06), one might conclude that the problem of obesity has been just a little bit exaggerated. I am very pleased to see someone prepared to counter the prevailing claims.

    1. Paul Rogers

      logged in via Twitter

      In reply to Sam Chafe

      I must admit I have been amazed how certain studies of 'body mass index (BMI) and health' have got through the peer review system in certain journals in recent years -- because they have been absolutely useless and misleading.

      For such studies to be useful, they need to control for putatively healthy (1) athletes, footballers, bodybuilders etc with BMIs over 25 because of muscle; and (2) for lean people who are ill -- depressed, smokers, cancer etc, with low BMIs because of their illnesses.

  9. Dale Bloom


    Just some quick questions that I cannot find an answer to in the research link.

    “Thirty-six healthy individuals undertook 28 days of overfeeding”

    The question are :Were these people in agreement with this, and were they told of possible risks?

    Also, what are the processes that someone has to go through at the Garvan Institute to get approval to carry out experiments that could endanger someone’s health?

    These questions may seem somewhat unusual, but I have recently read of some research conducted in an Australian university that has certainly made me think about such issues.

  10. Frances Lockie

    Policy officer

    I don't agree with some of the language used in this article, but that's understandable given I approach the topic from a humanities background and from the perspective of a fat person. ThatI really appreciate the medical community talking about the fuzzy link between obesity and health, and I'm pleased that The Conversation is continuing with this topic.

    1. Peter Fox

      Medical doctor

      In reply to Frances Lockie

      Frances, I would advise you to peruse a recent article in The Conversation entitled "Why The Guardian’s correction won’t change your mind about Milly Dowler" (, which describes bias information processing ("people are very good at cherry-picking information that confirms their worldviews").

    2. Frances Lockie

      Policy officer

      In reply to Peter Fox

      Yeah, but you do the same thing, right? I mean, this article said that it is possible for obese people to be be healthy and you fixated on the stereotype of a fat person eating fried food.

    3. Peter Fox

      Medical doctor

      In reply to Frances Lockie

      Not exactly. The link between obesity and poor health outcomes is based on many years of research. Now, we have a retrospective study that has hypothesised that there MAY be a small subgroup of obese people who don't have such bad health outcomes.

      Obesity --> morbidity/mortality: this is the consensus opinion. No cherry picking involved.

      (That's not to say the hypothesis is incorrect, but in the meantime it remains that, a hypothesis)

  11. Rob Abbott

    Project Manager

    I’m sorry, but it was always my understanding that insulin does not “help burn up glucose in the cells”, but rather it forces the production of glycogen in the liver and muscles and whatever is left over is used increase lipid synthesis and have fat cells store more blood lipids.

    Obese people often do have metabolic syndrome due to chronically elevated levels of Insulin, which does leads to decreased insulin sensitivity (or insulin resistance), which in turn leads to leptin resistance and chronic inflammation.

    I still don’t believe that there is such thing as a ‘metabolically healthy’ obese person. By definition being obese means you have larger than normal fat cells. Fat cell are an endocrine organ in themselves and produce various hormones such as leptin that in excess will cause metabolic disease.

  12. John Wright


    Lesley an excellent article and at last someone in Australia talking about insulin resistance in the context of obesity. I look forward to reading where your research conclusions lead particularly with respect to nutritional recommendations.

  13. Kath Read

    IT Librarian

    One thing I think gets ignored in this whole topic - nobody is under any moral obligation to be healthy. Health is not a virtue, it's a blessing and a privilege. Measuring people's health does not give an indication of their value as a human being.

    If you want evidence of cherry picking, look at how people cherry pick arbitrary illnesses to have empathy for, and then heap scorn on others. They pity the poor people with cancer (regardless of whether or not lifestyle choices brought it on) but heap scorn on the so called "obesity diseases" like diabetes or hypertension. If that's not cherry picking, what is?

    No matter someone's health, body shape or physical ability, every human being deserves to live their life in peace without vilification or discrimination. And as I have said before:

    If it is not your body, it is not your business.

  14. Sam Chafe

    Retired scientist

    Well said, Kath Read.

  15. Guy Hibbins

    Clinical evaluator of therapeutic goods at Monash University

    The trouble with the notion that you can have metabolically healthy obese people is that it does not take into account the duration of obesity.
    If a person gains 30kg they are not likely to immediately develop insulin resistance. This takes time. Insulin resistance develops as a result of increased demands on the body's insulin production and insulin receptors over time.

    The real test of the "healthy obese" concept is how many obese 80 year olds there are. In practice BMI peaks at around…

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  16. John Harland

    bicycle technician

    The stereotypes bother me as a fairly thin person, as well.

    For some years I had medical people telling me that I was grossly underweight. They failed to take into account that I have very long legs for my height and my torso shape was actually fairly normal.

    How many people have been judged to be overweight because their legs are short and their torsos long?

    It has also troubled me for some time that several of my women friends are classified (or condemned, perhaps) as obese despite being capable of cycling hundreds of kilometres at a stretch, quite rapidly, or bushwalking in circumstances that daunt me. I have no trouble with the concept of healthy but moderately obese people.