Sleeping in on the weekends can make you fat.
A German study found that a person's odds of being overweight increase
33 percent for every hour of difference between their weekday and
weekend sleep schedules. Two out of three people effectively commute
between two time zones each week, disrupting their circadian rhythms.
That "social jet lag" leads them "to eat at times when the body doesn't
want to eat or isn't prepared for digesting food properly," thus leading
to weight gain, says study author Till Roenneberg.
Too much exercise may hurt you more than it helps.
While being a runner lowers your risk of early death by nearly 20
percent over not running, running more than 20 miles per week appears to
cancel out that benefit. Jogging slowly decreases mortality risk,
whereas running at a pace faster than 8 minutes a mile has been found to
put extra stress on the heart. Studies have shown that more than an
hour of intense aerobic activity per day can cause serious heart
problems — including scarring, an irregular heartbeat, and clogged
arteries. Many people wrongly assume that "if moderate exercise is good,
then more is better," says study author James H. O'Keefe. But beyond an
hour, "you reach a point of diminishing returns."
Playing youth soccer can permanently damage your brain,
as can other sports that involve repeated blows to the head. Mounting
evidence shows that the routine hits young athletes take playing
football, soccer, lacrosse, and even volleyball can cause cognitive
problems. Girl soccer players have more concussions than any other young
athletes except football players. "What's happening in this country is
an epidemic of concussions," says sports physician Bob Cantu, who warns
that brain injuries can affect some young people "for the rest of their
lives."
Worrying about everyday problems will shorten your life.
A British study found that people who reported feeling even mild
anxiety — the sort that distracted them, depleted their self-confidence,
or occasionally kept them awake at night — were 16 percent more likely
to die over a 10-year period than people with no such concerns. About
one in four people experiences mild anxiety, but most go untreated. Mild
stressors — including those surrounding work, finances, and
relationships — are so common that they're virtually impossible to
avoid, but psychiatrist Glyn Lewis says exercise, meditation, or talk
therapy can tame "their biological impact."
Breathing city air raises your risk of heart attack and stroke.
After analyzing a decade's worth of data, researchers found that Boston
residents were 34 percent more likely to have a stroke following a day
of "moderate" as opposed to "good" air quality, under Environmental
Protection Agency standards. In reality, "there is no safe level" of air
pollution, says Johns Hopkins professor Roger Peng. Inhaling fine
particles from car exhaust and power plants can damage the heart and
lungs in much the same way cigarette smoke does: by clogging arteries,
increasing inflammation, and raising heart rate and blood pressure.
Breathing indoor air isn't safe either.
Exposure to carbon dioxide — even at levels considered in line with
good ventilation — can make you dumber. Researchers tested the reasoning
skills of volunteers while exposing them to different levels of CO2 and
found that as levels increased, the volunteers' strategic and
leadership abilities worsened to a degree "so astonishing that it was
almost hard to believe," says epidemiologist Mark Mendell. Alarmingly,
the highest levels of CO2 that he and colleagues measured, 2,500 parts
per million, can easily be found in buildings — including schools — that
are in perfect compliance with current ventilation codes.
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