Yes, we all know that exercise is good for us. But why, exactly?
How does exercise make us healthier? Straight from this week's Scientific American---Here's what the top researchers have to say.
Why is Exercise Good for the Heart & Blood Vessels?
- Exercise produces forceful & frequent heart contractions which increase the blood pumping through the arteries. This results in subtle changes to the autonomic nervous system--the control center for the contraction & relaxation of our blood vessels--which leads to a healthy circulatory system and:
- Lower resting heart rate-fewer beats to pump the blood through the body
- Lower blood pressure
- A more variable heart rate (a good thing)
- Lower inflammation levels. High inflammation levels lead to nasty things like atherosclerosis (hardening of the arteries) which leads to heart disease and stroke.
- New exercisers on average drop their C-reactive protein levels (the measurement of inflammation) about 30%, the same drop that occurs on a statin.
- Decreases in the triglyceride levels. High triglycerides are associated with heart disease & stroke
- Increases in the good cholesterol--the HDLs--which help prevent atherosclerosis--but not everyone's HDLs increase with exercise!
- News to me: the increase in HDLs from exercise is variable, based on genetics, from a 0-25% increase. Only about 1/2 of us experience an increase. Mine increases, but my husband's levels never budge, in spite of all his exercise.
How Does Exercise Affect Cancer?
- Exercise lowers the risk of some cancers, like breast & colon cancer.
- Experts aren't quite certain how this really works, however. Here are the current explanations.
- Exercise lowers body weight, which lowers the circulating levels of insulin--a good thing--because it prevents insulin-resistance.
- Overweight people often develop insulin-resistance--then the pancreas overcompensates & literally floods the bloodstream with insulin--which is like a growth hormone for cancer. The extra insulin can create tumors or make small tumors grow. Not a good thing.
- Exercise tunes up the body's immune system, making it better able to fight off cancer.
- It reduces levels of estrogen & progesterone in women, which lowers the risk of developing breast & uterine cancers.
- The skeptics view: it's possible that exercisers also eat healthier diets, which could also contribute to their reduced levels of cancer.
Exercise and Stronger Bones
- Exercise increases & maintains bone mass & reduces the risk of osteoporosis
- Fracture risk is much greater if you don't exercise
- Bones get stronger when they have to bear more weight than normal. The skeleton is smart--it knows how much force you are putting on it. Challenge your arms & legs with exercise & you stimulate the bones to build new tissue.
- Scientists aren't quite sure how this works, but they speculate that exercise triggers the mature bone cells (the osteocytes) to instruct the bone-building cells (the osteoblasts) to beef up bone formation.
Exercise and Type-2 Diabetes
- Exercise can prevent and even reverse Type-2 diabetes
- Again, it's all about insulin resistance. Too much body weight or a not-so-healthy diet & insulin-resistance develops--then the body can't absorb all the glucose from your digested food. This leads to a build-up of fats in the body which further interferes with the whole glucose transportation system. If the body can't absorb all the glucose in the blood, bad things can happen: like heart disease, nerve damage, blood vessel damage, stroke, or infections.
- Exercise can reverse the whole process. With vigorous exercise the muscles increase production of an enzyme called AMPK, which breaks down the fats that were interfering with the cells' glucose transportation system. Bingo--the body starts responding to insulin and absorbing glucose just like it's supposed to do.
- The skeptics view: Not all Type-2 diabetics respond to exercise in the same way--just like not everyone responds to medicine in the same way. Not everyone who exercises loses the same amount of belly fat (the nasty visceral fat)---and belly fat is a risk factor for Type-2 diabetes. Win some lose some.
How Does Exercise Make You Smarter?
- The effect of exercise on the brain is a relatively new discovery.
- It increases a chemical called BDNF (brain-derived neurotrophic factor) which helps the brain cells to grow, survive and better communicate with each other.
- The more one exercises, the more positive brain changes are seen.
- People over 50 with memory problems improved their scores on cognitive tests by 20% after 6 months on an exercise regimen.
- Exercise improved executive-control brain functions, like task coordination, planning & the ability to switch tasks.
- Exercisers show increases in brain tissue volume, increases in speed and sharpness of thought, as well as changes in the way their brains function.
- Post-menopausal women who exercise have more gray matter and do better on tests of executive control than less-fit women, irrespective of whether they had hormone replacement therapy.
Exercise and Weight-Loss
- Exercise leads to weight loss only if you can control caloric intake. Period.
- Since it takes 3600 calories to lose one pound, if you are only burning 1000 calories a week through exercise, it will take you 3 1/2 weeks to lose a pound--assuming you don't eat any more food than you ate before you started exercising. That's pretty discouraging.
- For most people, it's much easier to lose weight by lowering calories along with exercising.
- Vigorous exercise may suppress a key hunger hormone, called ghrelin, for up to 30 minutes after a workout, and increase an appetite-suppressing hormone, called peptide YY, for 3 hours after exercise. To that I say, "Big deal!"
- For many, exercise encourages healthier food choices--which leads to weight loss.
- Does exercise increase your appetite & sabotage your weight loss? The experts say no. Any increased calories won't translate into extra weight. Or so they say!