Exercise will speed up your metabolism, the
harder you exercise, the more energy you use. Lying quietly in bed, a 150-pound
person will burn about seventy-five calories an hour. even though the brain
uses about 20 percent of the body's energy, mental work won't increase that
significantly. So, alas, reading this book won't help you lose weight. In
contrast, a top athlete can burn fourteen hundred calories in an hour of
maximum exertion. Ordinary people, of course, may not work that hard, but
reasonable exercise will increase your metabolic rate by four to six times,
vigorous exercise by more. The most obvious metabolic benefit of usual exercise
is weight control.
If you exercise regularly, you'll burn away
body fat—but only if you use up more energy than you take in. The key to weight
loss is a "C" word, but despite America
Exercise training will also improve your
blood cholesterol profile. It will lower your LDL ("bad") cholesterol
and boost your HDL ("good") cholesterol. Over time, walking just a
mile a day will produce helpful gains, but the more you exercise, the more your
HDL will rise. That's particularly important, since the marvelous statin drugs
and most other medications that lower LDL levels are not very good at raising
HDL levels. Most people can expect moderate exercise to boost their HDL levels
by at least 5 percent, thus reducing the risk of heart attack by more than 15
percent. Exercise will also lower levels of triglycerides, a less dangerous but
still important form of blood fat. A good diet and successful weight control
will augment the beneficial effects of exercise. Healthy people should aim for
an LDL level below 130 mg/dL, but people with other risk factors, such as
diabetes or high blood pressure, should aim to get below 100 mg/dL, and people
with active coronary artery disease should set their sights on 70 mg/dL or even
less. The lower the better, but sharp reductions usually require medications in
addition to diet and exercise. Men should try to boost their HDL levels above
40 mg/dL, women above 45 mg/dL, the higher mean the better.
Exercise also has positive effects on
glucose (sugar) metabolism. It makes tissues more sensitive and responsive to
insulin, the hormone that allows glucose to move from the blood into the body's
cells, where it can be burned for energy. The result is a sharply lower risk of
diabetes, a major health hazard that is rising at a worrisome rate in our
sedentary, increasingly obese society. Pasting blood sugar levels of 100 mg/dL
or less are considered normal, levels of 126 mg/dL or more indicate diabetes,
and values between the two suggest an increased risk of developing diabetes.
