PhilGoetz comments on Rationality Case Study - Ad-36 - Less Wrong

22 Post author: Perplexed 22 September 2010 06:32PM

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Comment author: PhilGoetz 27 September 2010 09:00:00PM 0 points [-]

Epidemiologically AD-36 is entirely wrong, weight increase is broad process affecting most people, and viral origin would predict one subpopulation being strongly affected, while everyone else wasn't at all.

Since this subpopulation would be based on genetics, which are largely invisible, how do you know this isn't the case?

Comment author: taw 30 September 2010 01:55:26PM 2 points [-]

Weight distribution is not bimodal. Unless nearly everybody got infected by AD-36, but some people just a bit and some a lot more, you would get bimodal distribution.

Or to put it more drastically - AD-36 story predicts median weight barely changing in spite of skyrocketing mean weight.

Comment author: NancyLebovitz 30 September 2010 02:14:08PM 3 points [-]

My impression is that mean weight has changed very little-- 7 to 10 pounds, with the actual increase being about 25 to 30 pounds at the high end.

The definition of obesity was changed in the 90s.

More details

Comment author: taw 01 October 2010 01:04:13AM 2 points [-]

Now is your chance to be delighted by discovering truth! Here's one summary:

Results The age-adjusted prevalence of obesity was 30.5% in 1999-2000 compared with 22.9% in NHANES III (1988-1994; P<.001). The prevalence of overweight also increased during this period from 55.9% to 64.5% (P<.001). Extreme obesity (BMI >=40) also increased significantly in the population, from 2.9% to 4.7% (P = .002). Although not all changes were statistically significant, increases occurred for both men and women in all age groups and for non-Hispanic whites, non-Hispanic blacks, and Mexican Americans. Racial/ethnic groups did not differ significantly in the prevalence of obesity or overweight for men. Among women, obesity and overweight prevalences were highest among non-Hispanic black women. More than half of non-Hispanic black women aged 40 years or older were obese and more than 80% were overweight.

Every part of weight distribution was affected.

Comment author: Douglas_Knight 01 October 2010 02:27:06AM 0 points [-]

Your comment doesn't address Nancy's factual claims. What do the thresholds in your quote tell you about average values? Interestingly, her link is all about how awful thresholds are! The male graph in your source matches the graph in hers, which, by my eyeballing, matches her numbers. The female graph looks different because females are shorter, but I think the pounds are about the same.

As to your original claim, yes, the graph shows that the distribution is not bimodal. But the mean is moving faster than the median.

Comment author: taw 02 October 2010 01:48:38AM 1 point [-]

Your comment doesn't address Nancy's factual claims. What do the thresholds in your quote tell you about average values? Interestingly, her link is all about how awful thresholds are!

You see increases for every threshold - that is whole distribution moving. And this is just a few years and one country of process that is world-wide and lasts for at least four decades now.

Comment author: NancyLebovitz 02 October 2010 12:38:51PM 2 points [-]

Part of your original claim was that mean weight is skyrocketing. How much has it actually increased?

Comment author: taw 03 October 2010 04:55:43AM 2 points [-]

Oh yes, because we all live in fantasy world where quality historical data is easily available... What is wrong with you people...

Anyway, I dug through to what are pretty much punched card readouts from NHANES I dataset that somehow nobody ever bothered to convert to anything more reasonable.

Here are 10th to 90th percentile of weight in kg, height in cm, and BMI (including children):

  • 18.37kg, 37.76kg, 51.14kg, 56.81kg, 61.46kg, 66.45kg, 71.78kg, 78.13kg, 86.75kg
  • 109.3cm, 144.9cm, 155.5cm, 159.1cm, 162.2cm, 165.2cm, 168.4cm, 172.4cm, 177.4cm
  • BMI: 15.7, 17.6, 19.6, 21.1, 22.5, 24.0, 25.6, 27.5, 30.5

Age >= 18 only:

  • 52.16kg, 56.81kg, 60.55kg, 64.3kg, 68.15kg, 72.23kg, 77.0kg, 82.33kg, 90.26kg
  • 155.3 cm, 158.4 cm, 160.9 cm, 163.3 cm, 165.7 cm, 168.2 cm, 171.1 cm, 174.6 cm, 179.0 cm
  • BMI: 19.7, 21.1, 22.3, 23.4, 24.5, 25.8, 27.1, 28.9, 31.8

NHANES I was 1971-75, already quite a bit into obesity epidemic. These are not anything like pre-epidemic numbers, but good luck finding data much earlier than that.

Data for 2007 says 26th percentile has BMI 25, 73th has BMI 30, so I'll linearly extrapolate median adult American BMI to be 27.3 - i.e. median person weights 13% more than if obesity epidemic stayed at early 1970s' level (and let's guess 20% more than if it never happened).

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