The Doctor Weighs In

We all know the devastating statistics:

· 13.5 million people in the US suffer from coronary artery disease

· 8 million people have diabetes type 2.

· 95,000 people are diagnosed every year with colon cancer, and a sedentary lifestyle increases the likelihood of getting this disease by 40%.

· People who don’t exercise have about a 60% increase in osteoporosis; 250,000 suffer from hip fracture every year.

· 50 million suffer from hypertension.

· More than 60 million people in the US are overweight.

You might conclude from the last bullet that obesity is the culprit. You’d be only partly right. Lack of physical fitness is the other culprit, regardless of percentage of body fat. Even if we take people with a high % of body fat (more than 25%), the relative risk of death from all causes in the fit person is half that of the unfit.

Exercise and the body.

The effects of exercise on the body are well known:

· Exercise increases HDL, the good cholesterol, by an average of 4.6%. This, in turn, results in a decreased risk of coronary artery disease.

· Exercise increases insulin sensitivity, reducing the risk of metabolic syndrome and diabetes type 2.

· Exercise strengthens the heart muscle, improving its function.

· Exercise increases bone size and density, reducing bone loss due to aging and osteoporosis.

· Exercise increases muscle strength, coordination and reaction time. Result: improved balance and stability; reduction in falls and bone fractures.

What about mind?

This is a truly fascinating story, and you can read about it in more detail in an article in Newsweek, March 26, 2007 , by Michael Craig Miller, MD, from Harvard Medical School . Here are the salient points:

· Exercise has been known for many years to give, during and after exercise an “endorphin high”. This is the feeling of satisfaction, well being, and increased self-esteem that many people experience. This effect is short term, on the order 1-2 days in duration.

· Aerobic exercise increases blood supply to the brain, thus increasing oxygen and nutrient supply to the neurons, and removing metabolic waste materials from the brain.

· Aerobic exercise increases the production of neurotrophic factors in the hippocampus.

What are neurotrophic factors?

When the nerve cells are getting organized to form the organ that we call ‘brain’ (a process that doesn’t end at birth, it actually continues until about age 20), they do it under the direction and control of peptides and proteins that are secreted by the nerve cells themselves. But the job of these factors doesn’t end there: they continue to shape, modify, and re-shape several areas of the brain. They are essential for the formation of new neurons from stem cells—a process called neurogenesis. They also are important in the formation of new connections between existing neurons—a process called neuroplasticity. These two processes are important because they are the basis for learning and memory; everything we know and remember is stored in neuronal circuits. Furthermore, the thicker the connections between the neurons the faster the flow of information in the circuits—very much like the broadband required for fast transmission of electronic signals. The brain factors cause this thickening as well.

There are several known neurotrophic factors that have been shown to increase in concentration due to a sustained, long term exercise regimen:

· BDNF (Brain-Derived Neurotrophic Factor).

· NPY (Neurpeptide Y).

· VEGF (Vascular Endothelial Growth Factor).

The fact that we can identify specific brain peptides that increase neurogenesis and neuroplasticity is interesting enough. But what makes it even more fascinating is where in the brain this increase happens.

Enter the Sea Horse.

In the temporal lobe of the brain there is an area, called the hippocampus, because it is shaped like a sea horse. This area regulates emotions and stores memories. In fact, it has been known that in aging brains and in depression, two situations in which neurogenesis and neuroplasticity are reduced, the hippocampus gets smaller. Furthermore, electroshock therapy and antidepressants caused an increase in the size of the hippocampus, apparently due to increase in neurogenesis and neuroplasticity.

It was especially gratifying to read in the latest Proceedings of the National Academy of Sciences (PNAS, vol. 104, p. 4647, 2007) the report by Warner-Schmidt and Duman. The unequivocally demonstrated that the antidepressant drug fluoxetine (Prozac) and the pain-control drug desipramine (Norpramine, Pertofran), cause a large increase in VEGF in a specific area of the hippocampus (The subgranular zone). Interestingly, desipramine’s action is inhibition of pain signals ascending through the spinal cord to the brain; in other words, it inhibits the perception of pain.

Not surprisingly, aerobic exercise does the same thing. We even know how this happens on the molecular level—through the action of the very same brain factors: BDNF, NPY, and VEGF.

The take home lessons

· We now know beyond the shadow of a doubt that aerobic exercise increases the feeling of well being, increases learning capacity and improves memory.

· Aerobic exercise ameliorates depression and is becoming an additional tool in the treatment of this disease.

· Aerobic exercise reverses the effects of aging on the brain.

· Aerobic exercise may reduce the perception of pain—an important implication for people suffering from chronic pain, such as arthritis.

One final note: to all you Yoga practitioners, iron pumpers, and assorted other exercise enthusiasts—these effects on the brain were demonstrated only with aerobic exercise. Sorry.

Dov Michaeli, MD, Ph.D