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Lots of junk in your trunk: good for health?

Wednesday, January 20, 2010 Posted by Peter Janiszewski, PhD

Sir Mix-A-Lot once rapped:

“I like big butts and I cannot lie; You other brothers can't deny that when a girl walks in with an itty bitty waist and a round thing in your face you get sprung!”

Not sure how often this happens, but this may be the first time that a song predicted the outcome of future scientific research.

Very recently, a review published in the International Journal of Obesity has created quite the media buzz – I even caught a joke about the study featured in the Weekend Update of Saturday Night Live.

What’s the gist of the review, and why is it so important?

In the paper, Manolopoulos and colleagues review the research documenting the now well-established ‘health protective effect’ of having lots of butt and thigh fat.

Indeed, it wasn’t long ago that I discussed the results of an original study using prospective (over-time) data from 1436 men and 1380 women showing that for a given body mass index (BMI) or waist circumference, men and women with smaller thighs had an increased risk of dying and of developing cardiovascular disease compared to those with larger thighs. (Read more here)

Back in 2008, along with Drs. Kuk and Ross, I had published a study which clearly showed that for a given amount of belly fat, having more fat in the buttocks, hips, and thighs was actually associated with a healthier metabolic profile among both men and women. (Read here to find out why this may be the case).

All this evidence is often summed up to mean that pear-shaped people have better health than apple shaped people.

The recent review making headlines simply sums up the majority of research which suggests that lower body fat may be 'protective'. However, there are two major issues with the recent review as it is presented, and maybe even more how the findings have been (mis-)interpreted by the media.

Claim #1. Having a big butt is good for you.

Well, not exactly. If you simply look at a correlation between the amount of butt fat and most metabolic outcomes, the bigger the butt, the greater the risk. This is obvious given that most people with big butts are also big elsewhere. The observation of a protective effect of butt fat usually only comes into play after we consider someone’s total fat mass or obesity level (BMI, for example). Thus, if two people have the same BMI – the one with more butt fat will tend to be healthier. The same individual will also have less abdominal fat – another reason why they may be healthier.

Claim #2. If having a big butt is good for you, then losing butt fat must be bad.

Ok, I’ve gone into this in much greater detail before (read here). Basically, one study came out and stated this was the case. But, this study had a number of flaws which confound interpretation of the results. In response, we re-did the study using better methods and more appropriate analyses and published that study in Diabetologia back in 2008. In that study, we found no evidence that losing butt fat through diet or exercise induced weight loss is associated with any harm to health. In fact, we observed that reduction in butt fat may actually be good for health – just like reducing belly fat.

Unfortunately, in this recent review of the literature, the authors missed our study. Thus, one again, the media are running around claiming that people should not lose fat from their buttocks and thighs because it may negatively affect their health. Given that you can’t spot-reduce fat, the message simply becomes – do not lose fat or you will get sick.

This is a bit unfortunate in terms of a public health message.

In the meantime, just remember you can’t believe everything you read…

Peter Janiszewski

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Manolopoulos, K., Karpe, F., & Frayn, K. (2010). Gluteofemoral body fat as a determinant of metabolic health International Journal of Obesity DOI: 10.1038/ijo.2009.286

Janiszewski, P., Kuk, J., & Ross, R. (2008). Is the reduction of lower-body subcutaneous adipose tissue associated with elevations in risk factors for diabetes and cardiovascular disease? Diabetologia, 51 (8), 1475-1482 DOI: 10.1007/s00125-008-1058-0

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3 Response to "Lots of junk in your trunk: good for health?"

  1. Blake Said,

    Great.... now that song is gonna be stuck in my head for awhile! :)

    Posted on January 21, 2010 at 11:40 AM

  2. ERV Said,

    Note: If you are a journalist, and you'd like to do an accurate story on these often confused issues, please contact me for interview (peter [at] obesitypanacea [dot] com).
    Yeahhh... the only responsible science journalists I know are Ed Yong and Carl Zimmer.

    Actually, Ed might be up for an article like this... Email him the next time you have something cool published!

    Posted on January 21, 2010 at 5:54 PM

  3. Peter Janiszewski, PhD (Cand.), MSc Said,

    Thanks for the suggestion, ERV. I met both Ed and Carl at Science Online. I do have a couple of cool papers in the pipeline, so will contact them when they are published and see if I can get my work some more publicity.

    Posted on January 22, 2010 at 12:29 AM


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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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