BMI

lm446, Jan 2, 1:00pm
This may be of some interest to posters on here
http://www.motherjones.com/politics/2014/08/why-bmi-big-fat-scam/

"But there’s an even easier way for docs to gauge their patients’ risk level: Ask them how much they exercise. “It’s much more important to avoid low fitness than it is to avoid fatness,” Lavie says. Research supports this: McAuley and his team, for example, followed 831 veterans with type 2 diabetes for 10 years and found that the ones who exercised rarely and performed poorly on treadmill tests had a 70 percent higher death risk than those who got regular exercise. Fitness, it turned out, beats BMI as a predictor of mortality. Yet many physicians still don’t prescribe exercise: In a 2013 study, Lavie and his colleagues found that only a bit more than half of diabetes patients—and just 44 percent of those with hypertension—reported being counseled to exercise more."


huggy5, Jan 2, 1:11pm
I read the study that is referenced there, the benefits of fitness apply across all BMIs but the rate of death is still higher in the higher BMI participants.
So all it tells me is that no matter how fat you are, you should exercise, but you're still better off being of a normal weight for your body type.

lm446, Jan 2, 4:03pm
And it also tells me that BMI is unreliable when taken alone

hoarder85, Jan 2, 4:09pm
True, but it's commonsense that if two people have a BMI of 40 and one exercises regularly and the other doesn't that the one who exercises will be 'healthier'.

Pretty sure when the doc measures you and calculates your BMI the first thing they say to you is 'how much do you exercise?', followed by what's your diet like.

I know when I go to my GP as a person with a fairly normal BMI my Dr asks how often I exercise. Should be standard practice.

buzzy110, Jan 2, 5:46pm
I know exactly where you are coming from. I fail to see why people need to split hairs. The researchers have done their research and come to a conclusion. No amount of doctors asking about exercise and diet will alter those conclusions. Only other research can achieve that.

buzzy110, Jan 2, 5:57pm
Anyway it is this sentence that intrigued me much more:

". 97 studies covering nearly 3 million people and concluded that those with overweight BMIs were 6 percent less likely to die in a given year than those in the normal range. These results were even more pronounced for middle-aged and elderly people. This is known as the obesity paradox."

There is such a thing as an OBESITY PARADOX! How can there be? If obese people live longer then it is not a paradox.

Take the French Paradox, which has researchers and commentators alike flummoxed as to why the French remained healthy despite their high fat diet. The reality was they were healthy BECAUSE of their high fat diet.

Which leads me to speculate that one day they will be saying that obesity is what kept these people alive. This would be because of the low numbers on the BMI scale that people stop being 'normal' and are declared obese were totally unrealistic/out of the ball park of what is reasonable/risible.

rosess, Jan 2, 9:51pm
I read the original study, i think it was in Nature, will look it up. From memory, in the original study, all cause mortality was higher in the low BMI group compared to those in the just overweight BMI range (~25). However as mentioned by the authors in the original study, they did not rule out intercurrent illnesses leading to wasting in the low BMI range e.g cancer and renal disease. A more recent report which controlled for wasting disease in the low BMI group nullified the original findings. If you are interested I will try and find the refs for you.
ETA It is referred to as a paradox because all-cause mortality increased with increased BMI (i.e. those with BMI of 30 + had higher death rates than 25-30) however there was a spike of increased death rate in the the low BMI range (<20).

ETA when i was unwell and my BMI dropped to below 18, I was warned by my surgeon that I was at an increased risk of post surgical complications, as well as infection and respiratory infection because of my wasted state.

buzzy110, Jan 9, 1:31pm
Thanks rosess. Getting a more complete picture is enlightening. It seems that the wide eyed wonder that lead to the coining of the Obesity paradox phrase lead to a slight case of exaggeration.

Basically it has been understood for yonks that people who are fatter/heavier die earlier from all causes (which I presume is what is meant by higher death rates) than their normal weight peers. I fail to see how that is a paradox.

But when coining lovely new catch phrases such as "the obesity paradox" researchers should be a tad more careful. Including those with wasting disease in their findings is a nonsense as those people could just as easily have started out in the overweight category. It would appear, from what you say, that there is barely enough evidence to warranted the catch phrase unless there was sufficient evidence of large numbers of people who are both healthy and have a naturally low BMI, kicking the bucket prematurely from all causes.

How likely is that I wonder?

bernie184, Jan 10, 11:23am
So what is the difference in death rates between someone who is normal weight and someone who has a BMI of 40? What is the difference between someone of normal weight who doesn't exercise and someone who does, and the same for the person with the BMI of 40? What is the difference between the active over weight 40 and the inactive? And is the person with the 40 BMI who exercises regularly actually better off than the normal person who never gets out of their chair?

pico42, Jan 7, 4:45pm
Not quite. It tells you (correctly) that BMI alone is not a final arbiter of ones health, fitness or life expectancy.
BMI remains reliable, as long as its limitations are recognised.

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