Gabe Mirkin, M.D.
Can you explain why a study from The University of
Sherbrooke in Canada showed that exercising three times a
week improved insulin sensitivity in younger women but not in
older women? (European Journal of Applied Physiology, October
2005) Insulin sensitivity measures the ability of your cells to
respond to insulin. When cells fail to respond adequately to
insulin, blood sugar levels rise too high, and you are more likely
to suffer diabetes, obesity particularly in the abdomen, high blood
pressure, heart attacks, strokes and nerve damage. Inability to
respond to insulin is the most common cause of diabetes in
North America. Exercise helps your cells respond to insulin
because exercise empties muscles of their stored sugar. Empty
muscles can absorb sugar from the bloodstream whenever you
eat and prevent blood sugar levels from rising too high.
Thirty-five percent of adults in North America will become
diabetic because they eat too much and exercise too little,
because being fat fills your fat cells with fat, which blocks insulin
receptors and prevents your body from responding to insulin.
Insulin prevents your blood sugar from rising too high, particularly
after you eat. So when your cells do not respond adequately to
insulin, your pancreas produces very large amounts of insulin,
which constricts coronary arteries to increase your chances of
suffering a heart attack, stimulates your brain to make you
hungry and causes fat to be deposited in your belly.
The only places that you can store extra sugar in your
body are in your liver and muscles. When you eat, sugar passes
from your intestines, into your bloodstream, and then into your
muscles and liver. When your muscles are full of sugar, sugar
can only enter your liver, and your blood levels rise too high.
This causes sugar to stick to cells. Once stuck on a cell, sugar is
converted to sorbitol which damages the cells to cause
blindness, heart attacks, strokes, kidney damage and all the
other side effects of diabetes. This study showed that younger
women could exercise intensely enough to empty their muscles
on a regimen of three times a week, but older women could not.
So most older people need to exercise every day to deplete their
muscles of stored sugar. Younger people can exercise less
frequently and to get the same results, as long as they exercise
very vigorously during their three sessions per week.
May 1, 2006