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BMI: is lifestyle far more important?

With the printer’s ink just about dry on the latest issue of FitPro, I’m flicking through the pages trying to decide which features to read first. I read them all, of course, but like to start with something that might cause me to think differently about something that’s currently on my mind.

Having written about mental health and social media in my blog last week, the article, ‘7 ways to support your clients’ goals without body shaming’, by Kylie Ryan caught my eye. I found it extremely interesting and highly practical.

Talking about health, bodyweight, body image and obesity is never easy. I suspect this makes the job of anyone trying to carry out and report health research that much more difficult. At FitPro, we receive many press releases and we like to read them all. All universities now seem to have PR departments and we are regularly informed of each university’s latest studies. If you’ve ever wondered where most of the ‘science-y’ news items and features in newspapers and many magazines come from, wonder no more! Many print and online publications even publish the complete press release, often even including the spelling errors… So, if you’re occasionally left thinking that the health science stories in one paper are exactly the same as in another, and might also be written as if by a public relations officer with a university to promote, you’re right!

Anyway, one piece of research that almost nobody has picked up on (despite its obvious relevance to health) was published a few days ago in the British Medical Journal (1). I can’t help thinking that its lack of general media exposure relates to what some people might consider its currently unfashionable message.

The authors of this study first acknowledge that some research findings show that being lean is associated with greater metabolic health and a lower risk of developing type 2 diabetes, cardiovascular disease and cancer. However, they also report other findings that challenge this and indicate the opposite; “… that being overweight, and possibly even mildly obese, is associated with a reduced risk of mortality”.

The authors question both sets of findings and query the relationship between body mass index (BMI) and mortality risk, saying – quite obviously, I think – that “it might be important to consider lifestyle factors such as smoking, diet, moderate alcohol intake, and physical activity levels”.

So that’s what they did, using information from two massive databases which meant that they looked at statistics from 74,582 women and 39,284 men. In other words, it wasn’t a small study.

The conclusions reached, when factors other than just BMI (which we all know is a crude measure) are considered, are straightforward enough and I’ll quote the authors directly, although the words in italics are my emphasis: “Although people with a higher BMI can have lower risk of premature mortality if they also have at least one low risk lifestyle factor, the lowest risk of premature mortality is in people in the 18.5 – 22.4 BMI range, with high scores on the healthy eating index, high levels of physical activity, moderate alcohol drinking and who do not smoke. It is important to consider diet and lifestyle factors in the evaluation of the association between BMI and mortality”.

Here in the FitPro office, we have a checklist that we use when reading research papers. This piece of research follows a study design that sits high up in the ‘hierarchy of evidence’, so that’s good; as is the large sample size. The authors also comment on the limitations of this study (for example; “our cohorts include only health professionals, mostly white men and women, which might limit the generalisability of the findings”) and that’s also important.

Their very last sentence is effectively their take-home message; “Our findings indicate that leanness induced by healthy lifestyles is the optimal way to promote healthy longevity and to reduce the risk of premature death”.

My simple question is now this: is this socially-unacceptable (to some), yet research-based statement the reason why this appears to be an under-reported story this week? I’d be interested in your views:



[Veronese N, Li Y, Manson JE, Willett WC, Fontana L, Hu FB. Combined associations of body weight and lifestyle factors with all cause and cause specific mortality in men and women: prospective cohort study. BMJ 2016;355:i5855.]