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But there are significant risks for mortality with increased BMI!!

From a fellow dietitian:


"I do believe there are significant risks for mortality with increased BMI, irrespective of diet. I have seen studies supporting that, so I don’t think it’s a slam dunk for embracing any level of obesity. See the latest BMJ systematic review for example:


http://www.bmj.com/content/bmj/353/bmj.i2156.full.pdf"


Oooh numbers

My response:


My fingers get twitchy when I see this kind of research used to justify recommending weight loss, but I see it all the time and I think it's important to unpack the details.


The meta-analysis you've posted is a good one and can tell us many things. Mainly it shows that a group of larger people is, on average, likely to have a shorter lifespan than a group of smaller people. Interestingly, this one shows that smoking appears to be worse for you if you have a high BMI. The identification of the nadir of risk is great news for people who have a lower BMI relatively effortlessly despite living in an obesogenic environment that causes 2/3 of the population to creep up in weight over time (ie genetic jackpot). The recent influx of big BMI and mortality meta-analyses interestingly comes in response to Flegal's paper from 2013 which found that being overweight conferred the lowest risk of death in an NHANES dataset, thus suggesting that larger bodies might not be as bad as originally thought. Anyway, I digress. There are far more interesting things for dietitians in this study.


Firstly, where are our intentional weight losers (ie including our clients)? Well, we don't know. Unless they are running separate analysis for those who intentionally lost weight into a lower BMI category we cannot tell whether they have the same risks as so-called 'never-fat' people and so we cannot say that weight loss delivers on it's promise. This study found that using highest adult BMI when analysing mortality resulted in even lower risks for the lower BMI categories. So this might mean that all weight loss is bad, or it might mean that there are so few healthy people losing weight, keeping it off and not dying early that the disease-related weight loser stats drown them out. Think about that for a bit: there are more people actively dying from disease to the point that they are losing weight than there are people who have successfully, permanently lost weight. Probably a bit of both is true. Bottom line: population studies showing how bad obesity is do not justify recommending weight loss; they just show that being overweight/obese confers risk. They say nothing about the merits of no longer being obese or about the risks of becoming obese.


Clearly there are also issues with the assumption