difference between those who eat
without gaining weight ... and the
rest of us.
Whatever fad diet books tell
you, the single most
important factor affecting
weight gain is the ratio of
calories consumed to
calories burned. Eat more than you work off, and
you'll gain weight.
But in recent years we've witnessed a flurry of
research showing that there's more at work than
this simple formula. We all know (and loathe)
them: Those people who seem to eat and eat and
eat, but never gain weight. Why do some people
pack on pounds, while others subject themselves
to rigorous diets and workout regimens only to
struggle with stubborn belly fat?
The answer has a lot to do with that mystery of
mysteries, the metabolism, which like everything
is influenced both by one's genetics and one's
environment. The environment, in this case,
includes more than just nutrition and exercise; it
includes sleep habits, stress and chemical
exposures. Here's a look at some of the factors
scientists believe may be affecting whether or not
we put on weight. (Oh, and while this may sound
like an article ripped from a women's health
magazine, don't be fooled: You won't find miracle
pills or quick-fix workouts as solutions to these
causes of weight-gain. As with eating well and
getting enough exercise, there is neither a great
mystery, nor an easy solution to finding good
health.
1. Stress:
While research hasn't yet determined all the
factors in the stress-weight gain feedback loop,
there appears to be evidence that stress leads to
weight gain -- just as putting on a few pounds
can lead to stress.
One recent study found that more than 56% of
stressed-out adolescents were obese, versus 47%
of the less-stressed. Previous research has
identified a biological switch in mice that makes
the body accumulate fat. Significantly, mice that
were eating a healthy diet did not put on weight,
even when stressed; those eating high-fat, high-
sugar diets, however, were much more likely to
gain weight when stressed. Another study
showed that there's a biochemical trigger in the
brain that prompts mice (and possibly humans,
too) to seek out comfort foods when under the
kind of long-term chronic stress we all experience;
not only that, but the same hormone primes the
body to pack on belly fat.
WHAT YOU CAN DO:
Eat well, of course -- and chill out. We can't
control every form of stress -- remember the 40-
hour work week? Turns out, that was good for us
-- we can reduce our stress levels.
Read a book. Take the afternoon to cook a
(healthy, low-fat) family meal. Work in the
garden. Take a walk. Watch the birds. Exercise.
Get outside and play with the kids. ... Do
whatever you do to get perspective. It may help
you slim down, too.
2. Lack of Sleep:
Cutting-edge sleep researchers are learning that
our round-the-clock schedules may impact our
health in surprising ways. While scientists don't
yet know why, studies continue to show that
those who don't get enough deep restful sleep
tend to gain weight.
Whether or not losing sleep makes you feel
hungrier and eat more food (some do, some
don't) something about losing sleep changes the
metabolism. Faced with a sleep deficit, we
metabolize more lean muscle and less fat. Even if
we burn calories during exercise, we struggle to
lose weight.
The result? According to one study, people put on
three pounds in less than two weeks just by
having their sleep interrupted. The results of
sleep deprivation show up in as few as a couple
nights without deep restful sleep. And BMI, the
official measure of weight, increases steadily as
the sleep deficit increases.
WHAT YOU CAN DO:
We all know what makes us lose sleep -- too much
to do, too much coffee (or alcohol), too much
late-night television or video gaming, a little too
much "quality" time with our Blackberries. We
can't control everything that wakes us up or
takes away our sleep -- the crying baby can't be
ignored -- but we can control many of them.
How much sleep do you need? The Centers for
Disease Control and Prevention recommends 7-9
hours for adults, while some experts have said
6.5-7.5 may be closer to the ideal.
3. Baby Formula
What could be wrong with baby formula? The
point here has more to do with the benefits of
breast-feeding during the first months of life than
the demerits of any particular brand of baby
formula.
A number of studies have shown that children
who breast-feed are less likely to be overweight or
obese in their early years, which is good --
because an overweight child is more likely to
grow into an overweight adult. According toone
study, the risk of a child becoming overweight
declines the longer a child is breast-fed. By age
14, those who were breast-fed at least seven
months were 20% less likely to be overweight
than those breast-fed for three months.
Why? That's a mystery, though it may well have
something to do with how the different nutrients
and hormones alter a baby's metabolism.
WHAT YOU CAN DO:
If you are able, give your child a good start by
breastfeeding, in consultation (of course!) with
your doctor. A German study found the
prevalence of obesity in children aged 5-6
decreased significantly based on the length of
time their mothers breast-fed them:
Obesity rate - Duration of breast-feeding
4.5% - Never
3.8% - 2 months
2.3% - 3-5 mos
1.7% - 6-12 mos
0.8% - 12+ mos
4. Obesogens
Never heard of "obesogens"? That's because it's a
scientific term for chemicals that mess with the
hormones that regulate our metabolism, and
cause us to gain weight. In recent years,
scientists have studied all sorts of substances --
they call them "endocrine-disrupting chemicals"
-- that our bodies mistake for hormones. The
endocrine system regulates the body's
reproduction, development and metabolism, and
most research to date has focused on the
reproductive and developmental effects of these
chemicals. Just like hormones, they may change
our bodies in ways both subtle and profound,
even at minute concentrations. The timing of
exposure is key, and most chemicals seem to
cause the most changes when pregnant women
or very young children are exposed. Several
studies point to links between manmade
chemicals and weight gain. Here are a few:
Bisphenol A
This common chemical, which is used in a variety
of plastics and in the lining of food and drink
cans, can leach into foods (or directly into the
bodies of babies chewing on teethers or toys) and
the Centers for Disease Control and Prevention
has found it in about 9 of 10 Americans tested.
The Food and Drug Administration and the
chemical industry stand by its safety, but a
growing body of evidence by independent
scientists has persuaded several governments
(Minnesota, Chicago, Suffolk County, N.Y., and
Canada) that it should not be used in children's
products. Some of that research suggests that
Bisphenol A -- a synthetic estrogen -- makes lab
rats pack on extra weight, regardless of their diet.
In humans, it has been linked to heart disease,
diabetes and other symptoms of metabolic
syndrome in humans, possibly by interfering with
a beneficial hormone. To avoid Bisphenol A, avoid
No. 7 plastics, use a stainless steel reusable water
bottle, limit your consumption of canned foods
and drinks, don't microwave foods in plastic and
look for products explicitly marked "BPA free."
PFOA and PFOS
Perfluorooctanoic acid and perfluorooctane
sulfonate are the chemicals that makes nonstick
pans, grease-resistant paper and stain-resistant
clothing, carpets and furniture withstand oils.
We're exposed our entire lives, and the exposure
in the womb may be the most important,
according to one study. Several studies have
shown that the chemicals lead to lowered birth
weight, but one showed that the initial drop in
birth weight is followed by a rapid gaining of
weight that is associated with obesity throughout
life. To avoid these chemicals, think twice before
buying stain-resistant and nonstick products
(cast iron is one good alternative in the kitchen)
and limit your intake of fast foods, microwave
popcorn and other foods that may be wrapped in
grease-proof paper.
Phthalates
Another common chemical, phthalates are found
in soft plastics, fragrances and many other
consumer products. The U.S. recently banned the
use of several phthalates in children's products,
because of evidence that early exposure affects
the normal development of boys by reducing
testosterone levels. One study showed that adult
men with the most evidence of exposure to
phthalates had fatter bellies. To avoid phthalates,
avoid No. 3 plastics, and scrutinize the
ingredients of products for "fragrances" or the
acronyms DBP, DEP, DMP, DEHP, BxBP or DMP --
all of which signal the presence of phthalates.
Dioxins
Formed as a byproduct of burning, dioxins are
common and known to be harmful at minute
levels. (Whereas the Environmental Protection
Agency measures most pollutants in pounds, it
measures dioxins in grams.) Dioxin rains down
after being emitted by smokestacks, tailpipes and
fires, and it contaminates farms, leaving us to be
exposed when we eat meat, dairy and fish
products. One study showed that those who had
been exposed to the highest levels of dioxins were
five times more likely to have metabolic
syndrome, a collection of metabolic conditions
that includes obesity, glucose intolerance and
hypertension. To avoid exposure to dioxins,
moderate your intake of beef, pork and dairy
products, and choose lean cuts of meat to avoid
dioxin stored in fats.
Pesticides
Several pesticides are known or suspected to be
endocrine-disrupting chemicals. Among the
suspects is tributyltin, which was used in anti-
fungal boat paints and to kill pests on some food
crops, and which may trigger obesity. On golf
courses, workers who handled the pesticide
tricholorfon had an 85%-250% greater risk of
developing diabetes, depending on how
frequently they handled the chemical. Children
born to mothers with higher levels of the
pesticide hexachlorobenzene in cord blood were
"significantly more likely to be overweight and
obese" by the age of 6. In a recent study, rats fed
water laced with atrazine, a weed killer commonly
used on U.S. corn crops (but banned in much of
the world) gained 5%-10% more weight than rats
that weren't exposed to the chemical. Those fed
weed killer and a high-fat diet gained the most
weight, but even rats that ate a healthy diet
ended up about 5% fatter if they drank the
tainted water. To avoid these and other
pesticides, avoid using insect and weed killers
around the home, and avoid foods with the most
pesticide residue.
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