Weight
and BMI 1976-1980 to 2015-2018
Walter
Deal
wjdeal@san.rr.com
August 2021
Executive summary:
“The
rich get rich, and the poor get poorer.” (from the song “Ain’t We Got Fun”)
Or in weight/BMI terms:
“The thin stayed thin,
and the fat got fatter.”
There has been much
discussion of the increasing rates of overweight and obesity in the Unites
States and, indeed, much of the rest of the first world. In the United States, the average woman today
weighs as much as the average man in the early 1960s (about 170 pounds). Over 70% of Americans are overweight
(BMI>25) or obese (BMI>30); over 40% of Americans are obese.
This justified alarmism –
justified in terms of increased rates of heart disease, cancer, diabetes, etc.
– masks an important truth: the weight
gain among Americans is concentrated in the already-heavy. Specifically, the increase in the last 40
years in the weight of Americans in the lowest 10% by weight has been unimportant
(for women, from 111 to 119 pounds, an increase of 8 pounds, or about 7% of
body weight), while the increase of the weight of Americans in the highest 10%
by weight has been MUCH larger (for women, from 186 to 232 pounds, an increase
of 46 pounds, or about 25% of body weight).
What to do about the
“obesity epidemic” – nobody has a clue. It
is well established that only a small fraction of obese people on any
diet/exercise program lose a substantial amount of weight and, probably more
important, keep it off. Perhaps the only
thing that can be done to the already-obese is to encourage good health habits,
and offer palliative care. One can try
to lower obesity rates among children and teenagers, but society and often
their parent(s) present a different message.
See the table at the end for numbers.
Notes:
1. Data
were taken from various NHANES surveys. Here’s a link to the most recent one; the
references link to earlier surveys.
https://www.cdc.gov/nchs/data/series/sr_03/sr03-046-508.pdf
Note that these surveys do not represent a
longitudinal cohort survey of weights of a group of individuals over time; they
are snapshots of samples of people taken at various times.
2. For
simplicity, only data for women (all ages and races) are shown in the table. With some differences in the specific
numbers, the trends are the same for men and for various races/ethnic groups
(except, perhaps, for Asians, whose data were not separated out in the earlier
surveys).
3. The most striking result is the degree to
which the gain in weight, and increase in BMI, in the last 40 years is mainly
among people in the more overweight segment of the population. Again, the trend is the same for men as for
women, and the same among races/ethnic groups.
a. Women
in the 10th percentile weighed about 8 pounds more (7% of their body
weight), and had an increase of about 1.9 in BMI in 2015-2018 compared with
1976-1980. This weight gain for an
average woman in this percentile (the average height is about 5’ 4”) is clearly
unimportant medically, and the added weight is perhaps even marginally more healthy.
b. The
higher the percentile, the larger the increase in weight and BMI from 1976-1980
to 2015-2018. For example, the weight of
women in the 90th percentile was 46 pounds heavier (25% of body
weight), and the BMI 7.8 higher, in 2015-2018 than in 1976-1980. Again, contrast this increase to the increase
of only 8 pounds (7% of body weight) in the 10th percentile. If this 7% increase in weight and 1.9 increase
in BMI had been the same in the heavier percentiles as in the 10th
percentile, the “obesity epidemic” wouldn’t be on the radar for discussion.
c. The fraction of women who were severely obese
(BMI>35) was more than 20% as of 2015-2018; and the fraction who were
morbidly obese (BMI>40) was about 10%.
In 1976-1980, about 6% were severely obese and a very small percentage
were morbidly obese.
d. In 1976-1980, in a group of 100 women, about
42 would have been overweight or obese.
In 2015-2018, about 69 would have been overweight or obese, an increase
of 64%. This increase is mainly due to
the large increase in the number of obese women. That is, in a group of 100 women in
1976-1980, about 25 would have been overweight, and 17 would have been
obese. In a group of 100 women in 2015-2018,
about 26 were overweight, and 43 were obese.
This represents an increase of only about 4% (1/25) in the fraction of
overweight (but not obese) women, an insignificant increase. However, it represents a very large increase
of 153% (27/17) in the fraction of obese women.
That is, in a group of 100 women, more than twice as many were obese in
2015-2018 as in 1976-1980.
4. There has been much discussion of the
genetics of obesity, and even specific assertions that Blacks are especially
genetically disposed toward obesity.
However, it’s ridiculous to think that human genetics are any different than
they were 40 years ago, or that the doubling of the obesity rate has anything
to do with evolving genetics for any race.
Specifically, in 1976-1980, about 25% of Black women were obese; in
2015-2018, about 55% were obese. In
1976-1980, about 15% of White women were obese; in 2015-2018, about 40% were
obese – about the same greater than two-fold increase in obesity as among Black
women.
5. The
medical care for overweight (BMI 25 to 30) people has been estimated to be no
more costly than for people with a BMI below 25. However, the cost for medical care for obese
people (BMI>30) has been estimated to be about $1,200 per year ($100 per
month) higher than for people with a lower BMI.
The added medical costs for the 40+% of the adult population that is
obese (about 100 million people) are obviously enormous – perhaps $120 billion
(!!) per year.
6. As
obesity becomes much more common – more than 40% of both men and women are now
obese – obesity becomes much more acceptable in society. In the 1950s, 1960s, and 1970s, people –
especially young women – who were obese or even overweight were often ridiculed
and ostracized. In 2021, opprobrium is
focused on people who fat-shame.
One very obvious example of the acceptability of
obesity: Since the television age began,
no
nominee for the Presidency had been obese… until 2016, when both Donald
Trump and Hillary Clinton were clearly at least borderline obese. (Lyndon Johnson, Gerald Ford, Bill Clinton,
and George W. Bush were slightly overweight.)
