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Obese but healthy: Is weight loss detrimental?

Monday, July 06, 2009 Posted by Peter Janiszewski, PhD

Earlier this year I discussed the notion of metabolically healthy obese individuals - that is, individuals who are clinically obese (body mass index >30kg/m2) and yet who appear to have perfect metabolic health (normal blood glucose, blood lipids, blood pressure, and cytokine profile).

While countless epidemiological studies have shown that as you move from a normal weight (BMI = 18.5-24.9 kg/m2) towards overweight (BMI = 25-29.9kg/m2) and obesity (BMI ≥ 30kg/m2) the risk of many diseases increases exponentially, it is also true that approximately 25% of obese individuals ­are metabolically healthy despite their excess weight.

Knowing the above, the question then becomes: should every obese person be instructed to lose weight for health reasons?

According to a recent study by Karelis and colleagues from Quebec, otherwise healthy obese people who lose weight via dieting may actually WORSEN their metabolic profile.

In the study, a sample of obese women were divided into either metabolically healthy (20 women) or metabolically at-risk (24 women) based on their level of insulin sensitivity (a marker of diabetes risk - the more insulin sensitive, the better) as measured using the euglycemic-hyperinsulinemic clamp procedure. These women then underwent 6 months of a medically supervised dietary weight loss program consisting of approximately 500-800 kcal reduction in daily food intake.

After the intervention all women lost a significant amount of body weight (approximately 6-7%).

More interestingly, however, while the metabolically at-risk obese women showed a 26% increase in their level of insulin sensitivity, the insulin sensitivity of the metabolically healthy obese women actually deteriorated by 13%!

This finding is very unexpected, and as of yet has not been corroborated by another study. Nevertheless, it does raise the very intriguing possibility that weight-loss among otherwise healthy obese women is not only unnecessary but, in fact, counter-productive.

This finding falls in line with a recommendation paper by Drs. Arya Sharma and Robert Kushner published in the International Journal of Obesity earlier this year. In that paper the authors proposed a novel obesity classification system which not only assesses weight, but also health complications of excess weight. Germane to the above discussion, Sharma and Kushner recommend that among obese individuals who have “no apparent obesity-related risk-factors” the goal of patient management should be to simply avoid further weight gain, or maintain current weight, rather than to induce weight loss. (To read Dr. Sharma’s full discussion of the new classification system please visit his blog here.)

In essence, the idea that healthy obese individuals may not have much to benefit health-wise from weight loss is not that surprising – they are healthy to begin with! However, whether weight-loss may actually be ill-advised for healthy obese individuals needs to be investigated by future studies which look at health outcomes other than insulin sensitivity. For example, it remains unknown whether exercise-induced weight loss among healthy obese individuals could also result in metabolic detriment (doubtful). Also, we have currently no idea if the above finding also holds true among men.

More on this topic in the near future.

Peter

Karelis, A., Messier, V., Brochu, M., & Rabasa-Lhoret, R. (2008). Metabolically healthy but obese women: effect of an energy-restricted diet Diabetologia, 51 (9), 1752-1754 DOI: 10.1007/s00125-008-1038-4

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9 Response to "Obese but healthy: Is weight loss detrimental?"

  1. Richard Eis Said,

    Thin does not equal healthy. Something that I think society hasn't learnt yet.

    Posted on July 7, 2009 at 5:58 AM

     
  2. SC Said,

    "as you move from "

    By this, do you mean as an individual gains weight, moving from the <25 BMI category to >30 BMI category?

    Or do you mean as the eye looking at the statistics moves from looking at the <25 category to the >30 category?

    There's a big difference in general between saying "the first category has a lower risk than the third category" and "an individual changing from the first category to the third category gets a higher risk".

    Similarly, just because the >30 category has a high risk and the <25 category has a lower risk doesn't mean that changing from the >30 category to the <25 category results in as low a risk as the people who were in the <25 category to begin with.

    That's because the changing and the maintenance of that change can have an effect, as can the reasons that the individuals were in those categories to begin with.

    For example. Suppose fair-skinned people have a high risk of a certain skin cancer and darker-skinned people have a lesser risk. Me being fair-skinned, I want to lessen my risk, so I attempt to darken my skin. By sunbathing, say.


    It's a similar question when you're considering weight loss. You may have statistics that say that thin people have less of a risk of XYZ than fat people, but that on its own doesn't justify weight loss to reduce XYZ risk, because a fat person is never comparing their own risk with that of people who fit the description "thin". A fat person is comparing risks of being fat versus risks of changing to being a formerly fat person who is having to take severe measures to remain at a thin size.

    It's hardly surprising that the change in risk is not predictable simply by looking at the risk of those who were thin to begin with.



    I know this is a tangent to the main point of your post, but it does go straight to the heart of your question "should every obese person be instructed to lose weight for health reasons?"

    Posted on July 7, 2009 at 6:52 AM

     
  3. darya Said,

    I always have the same problem with this. I agree with you completely about metabolic health and risk factors. Why fix what isn't broken? But what about breast cancer, pancreatic cancer, dementia and all the other diseases strongly linked to obesity? Some of these issues are related to metabolic dysfunction, but hormonal imbalance (fat is an endocrine organ) is equally if not more important in cancer.

    Posted on July 7, 2009 at 1:24 PM

     
  4. Travis Saunders, MSc Said,

    Excellent point Darya. I think there is definitely something to what you are saying - metabolic risk isn't the only negative outcome of obesity (joint problems are another major issue which Peter and I tend to overlook).

    However, the research I've read suggests that most links between obesity and cancer are mediated by inflammation and metabolic risk factors, both of which are relative non-issues in metabolically healthy obese individuals. For example, hyperinsulinemia, inflammation, and dyslipidemia are all cancer risk factors, but none of them are present in metabolically healthy obese individuals. In the absence of those risk factors, I don't see why obesity should be related to much cancer risk at all. Although I don't know the literature as well, I would expect the same to be true for dementia.

    Estrogens are a little outside of my area of expertise. I would say that hormonal imbalance is important in *some* cancers (especially some breast cancers), but I don't think it trumps the risk factors listed above by any means when we talk about cancers as a whole. I'll concede that obesity in any form might increase estrogen levels, but I think that's a relatively minor issue if all of the other factors mediating obesity and cancer (insulin, glucose, inflammation, etc) are normalized in these individuals.

    Thanks for the very interesting comment. Please let me know if you come across any research on this area, especially anything on body fat distribution and estrogen or breast cancer risk.

    Posted on July 7, 2009 at 2:10 PM

     
  5. nutrprofe Said,

    There are many unhealthy ways to lose weight. Smoking is one example. Many people smoke to lose weight and refuse to quit for fear of gaining. Methamphetmine use among women often starts to become habitual when used as a weight loss aid. Crack cocaine is a highly effective weight loss medication.
    Fad dieting, laxative abuse and self-induced vomiting also fall in this category. All are more common than you might expect.

    Posted on July 7, 2009 at 4:40 PM

     
  6. darya Said,

    Thanks for your response, Travis. I'll definitely keep my eyes out for related papers.

    Other estrogen/sex hormone related cancers are endometrial and cervical. Prostate cancer too, but I'm not sure it is related to obesity specifically. It is certainly related to diet and lifestyle.

    Arthritis and osteoporosis are pretty serious conditions that can negatively impact someone's ability to lead a healthy life.

    I think we have to be very careful about what we tell people about health. Though some overweight people may be perfectly healthy, the vast majority are not.

    Let's get to the bottom of this cancer issue :)

    Posted on July 9, 2009 at 11:49 AM

     
  7. Travis Saunders, MSc Said,

    Hi Darya,

    I'm not sure exactly what you're getting at in your last comment. I don't think many people are under the illusion that obesity is healthy :) But unfortunately, long-term weight loss is unattainable for many/most obese people. So telling them they have to lose a large amount of weight is thoroughly unhelpful advice, because it is just not a realistic goal. More importantly, when people adopt healthy lifestyle choices but fail to lose weight (which is extremely common) they often go back to their old unhealthy lifestyle, without realizing that they were experiencing tremendous health benefits despite little to no change in body weight.

    As I'm sure you'd agree, society's focus on obesity has actually been very counter-productive when it comes to promoting healthier behaviors. This is why many of us are moving towards the "health at every size" mentality - if you eat well, exercise, and make other positive lifestyle choices, you are almost certainly at a lower risk of morbidity and mortality than someone who is lean, inactive, and eats a poor diet. By focusing too much on obesity, we have distracted most people from the more important issue of having a good healthstyle.

    I agree that we have to be careful what we tell people about health, but I would urge you to be careful not to overstate the dangers of obesity when the science says otherwise. For example, obesity is actually protective against osteoporosis due to the extra loading, and weight loss may actually reduce bone mass. Obesity's relationship with health is far more complicated and un-intuitive than any of us could have expected, so I would urge people to allow the science to inform their opinions on obesity, and not the other way around.

    Posted on July 9, 2009 at 1:14 PM

     
  8. Travis Saunders, MSc Said,

    PS Thanks for the challenging debate, I learn a lot from these types of discussions :)

    Posted on July 9, 2009 at 1:16 PM

     
  9. Darya Pino Said,

    Thanks Travis, I see your point. I hadn't considered the psychological aspects you mentioned and yes I agree with out about the importance of overall health over simply weight.

    I wonder about the importance of genetics in determining who does and does not benefit from weight loss. Do you get the impression that there is a large percentage of the population that can be just as healthy when overweight? I have trouble believing this would apply to everyone, since overeating in general can contribute to poor health.

    Posted on July 13, 2009 at 5:23 PM

     

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We are PhD students in the School of Kinesiology and Health Studies at Queen's University in Kingston, Ontario. Our research focuses on the relationships between obesity, physical activity, and health risk. This blog is our attempt to consider the many "cures" for obesity that we read about on a daily basis. Enjoy.

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