UK Council To Send Obese People 'Motivational' Texts Telling Them To Use Stairs

Qedward writes "Stoke-on-Trent City Council is sending texts to obese people in the area to help motivate them to lose weight. Examples of the texts sent include 'aim to eat a variety of fruit and vegetables each day,' 'aim to eat regular meals and keep a check on snacks and drinks' and 'maybe walk to the shops or use the stairs more often.' Over 100,000 people in the region are overweight or obese, the council said, and the texts are for those who are aged at least 18, have a body mass index of 25 or over and who have proactively signed up to receive the motivational messages."

Comments

BMI

[TranquilVoid]

BMI is designed as a measure of population weight, not individual. Mine is over 30, making me technically obese, yet I have so little body fat I cannot float in swimming pools, and only just in the ocean.

Re:BMI

[AthanasiusKircher]

True. BMI is hardly perfect... but it's a good first step. Kinda like "Did you reboot it?"

Actually, no it's NOT a "good first step." It's a fair to poor "first step." It's more like a troubleshooting procedure that's guaranteed to give bogus results in a significant percentage of cases -- i.e., where it's wrong or off so often that asking the question is almost more likely to lead you down the wrong path for many cases, rather than giving you useful information.

The BMI formula assumes that adiposity relates to height squared. It does not. This is a simple fact. When people get taller, their bodies scale in three dimensions, not two. So, for really tall people, it's guaranteed to say they are more fat than they really are, and for really short people, it's guaranteed to say people are at a healthy weight when their fat or even obese.

The only reason the BMI formula appears to work at all is because women are both shorter and tend to have higher "healthy" bodyfat percentages. The BMI ranges are more-or-less supposed to be the same for men and women -- that should be a major red flag to anyone who knows anything about bodyfat, since healthy bodyfat ranges for men and women are clearly known to be different.

So, the mean female height is less than the mean male height, but the mean healthy female bodyfat amount is higher. Thus, to have a formula that works for both sexes, you need something that doesn't accurately reflect a "normal" body being scaled up or down. BMI fits the bill, and thus it has been used for population studies to compare mean statistics for overall populations. For individuals -- which it was never designed for -- it's TERRIBLE.

You can immediately see that from the men vs. women problem. BMI says a short man who is in the middle of the height range for women should have the same weight as an average woman. Given what we know about bodyfat, that doesn't make sense. Or, a tall woman who's over 6' or something -- to have a "healthy" BMI she'd often have to look like a waifish model.

"But," you say, "it's still a good first step. It's a simple formula."

Nope -- doesn't excuse it. There are a number of studies that have shown that a number of even simpler measures are actually more accurate at predicting health problems, propensity for disease, etc. For example, simply measuring the waist circumference for men -- regardless of height -- has been shown to be a better predictor of health problems than BMI. Think about that for a moment. Clearly a guy who is 5' tall should not have a waist size the same as a 7' tall guy. But studies have shown that even measuring the waist and saying, "Is it bigger than X inches?" without knowing anything about height, weight, or anything else is a better predictor than BMI.

Yeah, BMI sucks that bad.

But could a simple formula do that much harm? Well, why not just modify that "simple formula" to make it more accurate? In the days when you had to calculations by hand or with a slide rule, a formula involving only an exponent of 2 and a division might make sense. But most people don't calculate BMI by hand anymore -- they plug things into some sort of web calculator or look at a chart.

We can easily fix BMI to make it much more accurate. First, just change the exponent. Logically, as I mentioned at the outside, squaring the height makes NO SENSE. You might think that cubing the height would be better, since the body expands in three dimensions, but it turns out that the male/female factor and other things that don't quite scale precisely with the cube of the height makes an exponent of 3 bad too.

Various empirical studies have suggested an exponent of somewhere in the 2.3 to 2.7 range would be better. But really, to get any accuracy at all, you'd have to at least consider separating the sexes. At that point, you could narrow the range of the exponent for males an

Re:i hate fat fucks as much as the next guy...

[Anonymous Coward]

Actually, if you RTFS, they signed up to receive the messages. So it's called for.

Re:correlation

[s.petry]

Duh, that is the secondary purpose for the texts.