Thursday, January 31, 2008

I need someone who's better at math than I am for this:

Ok, I've been wondering about this for quite a while so I did some research. I just can't figure out how to use the numbers I found to make sense for the thought I had.
I've been trying to figure out how the number of overweight/obese people in 1960 relates to the number of overweight/obese people in 2000 (and the growth thereof) as far as population and its growth is concerned.
So here are the numbers I found:
% of population overweight/obese by year:
1961-1962 : 44.8%
1971-1974 : 47.7%
1976-1980 : 47.4%
1986-1994 : 56%
2001-2004 : 66%

US population by decade
1960 : 179.3 million (80.3 million overweight/obese)
1970 : 203.3 Million (96.9 million o/o)
1980 : 226.5 million (107.3 million o/o)
1990 : 248.7 million (139.2 million o/o)
2000 : 281.4 million (185.7 million o/o)

Where I get confused is by the following numbers* that I came up with:

1960-1970 : population increased by 24 million, o/o increased by 16 million
1970-1980 : population increased by 23 million, o/o increased by 11 million
1980-1990 : population increased by 22 million, o/o increased by 22 million
1990-2000 : population increased by 33 million, o/o increased by 46 million (but if you take into consideration that the standard for o/o was lowered in 1998 so that 35 million became o/o overnight, then the increase for o/o between 1990-2000 was actually only 11 million). ETA: I didn't see the footnote** that said they used BMI over 25 for ALL years for counting overweight/obese people in the population. So, they went back and made people fat retroactively (I thought I had read somewhere that the overweight/obesity rate for people back in the 60's was 1 in 4, or 25%, not 44.8%, so that's why they're saying NOW that more people were fat back then than they were saying back THEN were fat, if that makes sense). No wonder this epidemic is manufactured, they keep changing the rules on us, not just today, but for 10 years ago, 20 years ago, 30 years ago, 40 years ago.
**(until a troll pointed it out to me and told me what a fathead, stupid woman I was and that I should stick to eating and leave the math to people smarter than fat old me. Hey, I'm old and my eyes don't always see the really fine print anymore, even with glasses. After it was pointed out to me, I had to go back and magnify the page to 150% so I could see the footnote number and then actually read the footnote.)
Now, I'm seeing this as actually showing that the rates of obesity aren't increasing as rapidly as the population, except for the period from 1980 to 1990. So, if there actually was an obesity epidemic, wouldn't that mean that the rates of obesity should be increasing more rapidly than the population?
Am I reaching an erroneous conclusion here? I've never had a statistics class, so I'm not sure if I'm figuring things correctly or jumping to a conclusion.
Any opinions?

*numbers are rounded
CDC link for % overweight/obese by year
link for population by decade


  1. I might be wrong, but I'm pretty sure that the percentages have nothing to do with the number of people in the US. Since they're a percent based on a factor of one, it just means that now 6.6 people out of every 10 instead of the previous 4.48 out of every 10 fit the technical definition of obese. Now, we all now how ridiculous those definitions are, but that's another discussion :)


  2. I've got a degree that's pretty math and science heavy. Percentages are relative, and I think you're looking at it in absolute terms.

    What they're looking for is this:

    Year A: 100 people in the population, 50 obese people. (50%)

    Year B: 150 people in the population, 50 obese people. (33.3% -- omg! A thinness epidemic!)

    Year C: 200 people in the population, 100 obese people. (50%, back to normal.)

    Year D: 400 people in the population, 300 obese people (66.6% -- OMG! Obesity epidemic!)

    They're looking for the percentages to stay roughly the same, and I guess they assume that the "baseline" - the right percentage of fatties - is 44.8% of us. Why they assume 1962 is a banner year, I dunno.

    (Which is why I tell my doctors "I'm not part of the obesity epidemic. My grandparents are fat." For crying out loud.)

    The rate of growth of the population is not really related to the rate of growth of obesity. (Well, not directly at least.) Any change in obesity levels is indicative of something happening of epidemiological interest: the problem is What, Why, Whether it's a Problem, and What to do about it, if anything.

  3. Arwen - thanks. I think what I was trying to get at was that, yeah, we're going to have more fat people because there are more people, but I couldn't figure out if the percentages of population increase were tied to the increase in overweight/obesity. Looks like they aren't. Oh well, another theory shot all to

  4. Posted for pieta from an email to me:
    I can't seem to get the comment posting to work on this computer. But here's my comment for the most recent post:

    The thing is... looking at your numbers, it looks as though the percent o/o has gone DOWN from 1990 to 2000 - if you take into account the 35 million "overnight" change.

    1990 : 248.7 million (139.2 million o/o) = 55.97% o/o
    2000 : 281.4 million (185.7 million o/o - 35 million = 150.7) = 53.55% o/o

    Both of which are lower than the 1986-1994 figure, and showing a downward trend, at that.

    To put it another way: the apparent 10% gain between 86/94 and 01/04 can be accounted for by the fact that about (35/281.4 =) 12.4% of the population became overweight overnight, combined with a 2% DROP in the obesity rate as measured with a consistent standard in both time periods.

    So much for the obesity epidemic.


  5. Yeah, that's what it looked like to me, I just couldn't figure out how to say it. thanks, pieta.


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