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Scientists had more bad news for couch potatoes saying they had
found that exercise can lower the levels of a "fat hormone" in the
body -- no matter how fat a person is. Their findings add to a growing
body of evidence that nothing works better than hitting the pavement
to prevent diabetes and heart disease. The team, at the Harvard
School of Public Health in Boston, found that, fat or thin, men
who exercised the most had lower levels of leptin in their blood.
If you get more exercise, you can lower your leptin levels, even
if your BMI stays the same. BMI stands for body mass index, and
is used by researchers around the world to calculate obesity. Scientists
have been intrigued since the hormone leptin was discovered, and
became excited when they found that injecting leptin into rats could
cause them to lose weight.
Sadly, the same is not true for humans. In fact, overweight people
have higher levels of leptin than lean people do, which suggests
the hormone, which controls appetite in rodents, is being overproduced
by the body for some reason. Five years ago, it was believed that
leptin research might offer a miracle solution to obesity and the
many health problems associated with being overweight.
As you get fatter, your body makes more leptin. But when you exercise,
the amount of leptin in the blood decreases. Most of the time, you
also lose weight, which means your risk of heart disease decreases
too.
The researchers looked at the dietary and lifestyle habits of 268
men aged 47 to 83. None of the men had heart disease, diabetes or
cancer. Men whose leptin levels were the highest weighed more, exercised
the least and ate more foods high in saturated fat and cholesterol.
The researchers also found evidence that the fattest men were starting
a tendency toward diabetes -- which in the early stages is marked
by an increased production of insulin.
Men whose bodies produce more insulin also tend to have increased
leptin levels. This would suggest that leptin might play a role
in diabetes. It is too early to say whether leptin levels could
be used to predict a person's risk of heart disease. But obesity
raises a person's risk of a heart attack and stroke, and our findings
provide evidence that physical activity may reduce the chronic disease
risk in men through changes in leptin levels.
Meeting of the American Heart
Association in San Diego March 3, 2000
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