Why Money Won't Buy Fat
If you have a job like
mine, in which a reasonably broad swath of American society presents itself to
you without any clothes on, this question no doubt has popped into your head:
Why are the poor so fat? That obesity is a characteristic problem of affluent
countries surprises no one. But why is it also characteristic that obesity
increases so dramatically as you go down the social scale?
This, of course, is not
the case in developing nations. In countries such as India, where my parents
emigrated from, being overweight is directly related to wealth and status and
is regarded as attractive. Thus, my father's rural family of farmers is thin
and wiry, while the elders in my mother's urban clan of higher caste and
wealthier stock are as plump as can be. When my sister and I, two scrawny
specimens of the American "upper-middle class," visit, we always evoke a good
deal of concern from relatives.
The first report I found to document the effect class has
on obesity was a 1965 study of midtown Manhattan residents. The researchers
found obesity was six times more common among women in the bottom third of the
social scale than among those in the top third. Subsequent studies, orginating
from California to New Zealand, confirm these findings. In a 1996 study in
Minnesota's Twin Cities, women earning under $10,000 a year weighed, on
average, 20 pounds more than women earning over $40,000 a year. In advanced
nations, low income is a more powerful predictor of obesity than any single
factor except age, though this relationship is weaker in men than in women. In
men, height is associated more strongly with status. On average, in developed
and undeveloped countries alike, richer men are taller.
You'd think weight would be like height. More money
means more food. So more food should mean more fat, just as it means more
height, right? And, in fact, in children this is exactly the case--at young
ages, certainly under age 6 in the United States, lower-income kids are less
likely to be obese than higher-income kids. By the time they are adults,
however, the relationship has inverted.
What's going on? As my
epidemiologist friends point out to me, when two things correlate, there are
always three possible explanations. One leads to the other. The other leads to
the one. Or some third thing is driving both.
T he downward mobility hypothesis. One
possibility is that obesity leads to lower income. Certainly the obese,
particularly obese women, face severe disadvantages in both the job and
marriage markets. And the evidence that this produces downward mobility is
distressingly strong. Almost half the women in the 1965 Manhattan study
belonged to a different social class than their parents, and those who had
moved down were significantly fatter than those who had moved up. More
recently, a landmark national study led by Steven Gortmaker, a Harvard
researcher, tracked over 8,000 people from age 18 to 25. It found the heaviest
5 percent of women were half as likely to get married and twice as likely to
become impoverished as others. Obesity affected a woman's economic prospects
more than even chronic illness. In men, however, shortness led to downward
mobility. One foot less of height doubled a man's likelihood of poverty. But as
Gortmaker points out, downward mobility explains only a small part of the
observed relationship of income to obesity. That makes sense. After all, the
gap also exists in countries such as Britain, where social class is more rigid
than it is here.
T
he genetic explanation. Could genetics be an
outside factor driving both obesity and poverty? The so-called "Danish adoption
study" lent some credence to the idea, finding that the obesity and social
status of adoptees depended on the social status not only of their adoptive
parents but also of their biological parents. The study inferred that parents
can give their offspring genetic traits that tip the scales toward both heavier
weight and lower status. Even so, inheritance accounted for at most a small
part of the stark effect of income on obesity.
T he gluttony and sloth hypothesis. So downward
mobility and genes matter somewhat but, ultimately, we're left with the obvious
explanation that in affluent societies the lower the income, the more people
eat unhealthily, sit around, or both. Unfortunately, measuring this directly is
notoriously difficult. Most people--especially the obese--fib about diet and
exercise and, when observed, tend to change their behavior. The differences
you're looking for are also quite small--a single calorie of extra daily intake
starting in childhood can translate into 10 extra pounds by the time you're 25.
Nonetheless, there's a good deal of indirect evidence--for example, TV watching
is linked to eating more and exercising less, and rises substantially as income
lowers. Given the weakness of other explanations, few experts doubt that
lifestyle is the most important one.
The question is why. It's
as if avoiding obesity were enormously expensive. But it's not--exercise is
free, and eating less junk food and meat and more produce saves money. Rather,
for the 30 percent to 70 percent with a genetic predisposition to obesity, it's
just horrendously difficult. Being motivated is vital, and motivation is what
seems to differ by class.
The 1996 Twin Cities study, for example, found marked
differences in weight concern. Although women earning under $10,000 were no
less successful when they dieted than women earning over $40,000, they were
one-third less likely to diet in the first place. They had a greater tolerance
for weight gain, saying it would take a 20 pound gain before they took action,
as opposed to the 10 pound gain that would trigger action in higher-income
women. They even weighed themselves less often (three times a month vs. seven
times a month).
This cultural-differences explanation certainly
accounts for why anorexia nervosa is mainly a disease of higher-income girls
and young women. Since obese men are less stigmatized, it may also explain why
wealthier men are not that much less obese than poorer men.
Still, if thinness really becomes the ideal in
every affluent culture--the way plumpness is in poor societies--it's curious.
Is this simply the nature of status--the rich will always find a way to
distinguish themselves from the poor? Or does richness breed an instinct for
longevity? Whatever the case, I'll know India has finally risen from Third
World status when I go back to visit my relatives and the first few words they
say are not "Eat, eat, skinny boy."
