The moment of truth has arrived, again. The holidays have passed, the bowl games are over and you have renewed your annual New Year's resolution to get back into shape... for real. Don't worry, you are not alone. According to the Centers for Disease Control (CDC), 63 percent of Americans have a Body Mass Index (BMI) in excess of 25 (defined as overweight), while a quarter are greater than 30 (obese).

Its not just kids that benefit from exercise. As we get older, those extra pounds start to affect other areas of our health, contributing to the onset of diabetes, hypertension and high cholesterol.

Several new studies in the last month have now built stronger links between our levels of physical activity and the health of our most important body part, the brain. Conditions such as dementia, Parkinson's, Alzheimer's and even mild age-related memory loss can be delayed by regular physical activity.

Shrinking brain

According to John Ratey, clinical associate professor of psychiatry at Harvard Medical School and author of "Spark: the revolutionary new science of exercise and the brain" (2008, Little, Brown), "Age happens. Getting older is unavoidable, but falling apart is not."

Starting at age 40, we lose about 5 percent of our brain volume per decade, but then at age 70 other conditions may start to accelerate the deterioration. As we age, our cells are less able to cope with stress from waste products such as free radicals.

In the brain, as this stress claims more neuron cells, the web of interconnections between neurons weakens. As we each have more than one hundred billion neurons with each having oodles of connections to other neurons, this gradual net loss is not as dramatic, at first. However, as we age, if this neurodegenerative process accelerates, then our general focus and memory loss as well as more serious conditions like Alzheimer's may appear.

What the aging brain needs is a pumped-up blood flow. Exercise-induced neurotrophins such as brain-derived neurotropic factor (BDNF), vascular endothelial growth factor (VEGF), as well as the neurotransmitter dopamine are needed to grow and fertilize new and existing neurons and their synapse connections. Ratay calls BDNF "Miracle-Gro for the brain."

Make new brain cells

Researchers at the National Cheng Kung University Medical College in Taiwan recently tested the effects of BDNF in the brains of mice of different ages. Half were trained to run a maze for 1 hour a day for exercise, while the control group did not exercise.

As expected, the researchers first found that neurogenesis, the creation of new neuron cells in the brain, dropped of dramatically in the middle-aged mice compared with younger mice. They also were able to conclude that exercise significantly slows down the loss of new nerve cells in the middle-aged mice.

Production of neural stem cells improved by approximately 200 percent compared to the middle-aged mice that did not exercise.

Increase blood flow

OK, that was mice. What about humans? University of North Carolina brain researchers recently found that older adult humans who regularly exercised had increased blood flow in their brains. They compared long-time exercisers with sedentary adults using 3D MRI brain-scanning techniques.

"The active adults had more small blood vessels and improved cerebral blood flow," said the study's senior author, J. Keith Smith, associate professor of radiology at UNC School of Medicine. "These findings further point out the importance of regular exercise to healthy aging."

The research builds on a host of other studies, summarized in an August review, that show a balanced diet and regular exercise can protect the brain and ward off mental disorders.

Helps manage glucose

Finally, in a report released last month, Scott A. Small, associate professor of neurology at Columbia University Medical Center, found that levels of blood sugar (glucose) have a direct effect on blood flow in the brain.

By testing 240 elderly volunteers, and using functional magnetic resonance imaging (fMRI), Small and his colleagues found a correlation between elevated blood glucose levels and decreased cerebral blood flow, in the dentate gyrus, an area in the brain's hippocampus that has a direct effect on our memories. This corresponds with Smith's findings by showing that exercise may help manage glucose levels, which will improve blood flow to the brain.

Small's previous imaging studies have shown that physical exercise causes an improvement in dentate gyrus function.

"By improving glucose metabolism, physical exercise also reduces blood glucose" Small said. "We have a behavioral recommendation — physical exercise."

Please visit my other articles on Livescience.com

The end of 2008 brings some discouraging news about our kids' brains and brawn. Recent results from an international math and science test show United States students are performing near the middle of the pack compared to other countries, while their levels of obesity continue to climb.

Historically, these two trends were studied independently with plans of action developed for each. However, several researchers and a new book have been making the case for linking these two problems by showing the effects of aerobic exercise not only on a student's fitness level but also on their test scores.

Last month, the latest (2007) TIMSS (Trends in International Mathematics and Science Study) scores were released. They compare fourth grade students from 36 countries and eighth grade students from 48 countries. They were tested on subjects that were common to all of the countries, including algebra, geometry, chemistry and physics. Overall, 425,000 students participated in the test, which is administered every four years.

In math, American fourth graders came in at 11th place of the 36 countries while eighth graders scored ninth out of 48. Hong Kong and Taiwan ranked first for fourth grade and eighth grade, respectively. In science, Singapore topped the list for both fourth grade and eighth grade, with U.S. science students taking eighth place and 11th place.

While the American math scores have improved slightly, the science scores have dropped. In 2003, U.S. fourth graders were in sixth place in the world and eighth graders were in ninth place.

Only 6 percent of U.S. eighth-grade students reached the TIMSS "advanced" level in math, compared to 45 percent of students in Chinese Taipei, 40 percent in Korea, 40 percent in Singapore, 31 percent in Hong Kong, 26 percent in Japan and 10 percent in

Hungary

Regarding student fitness, the most recent figures from the Centers for Disease Control and Prevention report that the percentage of overweight or obese 6- to 11-year-olds has tripled since 1980, with more than 125 million children at unhealthy levels.

Leaping backward

Ironically, one of the solutions proposed for raising test scores, No Child Left Behind, encourages schools to focus more of the school day on the core academic subjects while reducing class time in peripheral subjects, like art, music, and physical education. In fact, only 6 percent of American high schools offer a daily gym class. Yet a 2002 Virginia Tech study showed no relationship between reduced class time in those subjects and higher overall standardized tests.

In his latest book, "Spark: The Revolutionary New Science of Exercise and the Brain" (2008, Little, Brown), John Ratey, a Harvard clinical associate professor of psychiatry, argues for more physical fitness for students as a cure for not only their obesity but also their academic performance.

"I cannot underestimate how important regular exercise is in improving the function and performance of the brain." Ratey writes. "Exercise stimulates our gray matter to produce Miracle-Gro for the brain." That "Miracle-Gro" is a brain chemical called brain-derived neurotropic factor, or BDNF. When we exercise, our working muscles send chemicals into our bloodstream, including a protein known as IGF-1.

Once in the brain, IGF-1 orders the production of more BDNF. The additional BDNF helps new neurons and their connections grow. In addition, levels of other neurotransmitters are increased after a strenuous exercise session.

"Dopamine, serotonin, norepinephrine — all of these are elevated after exercise," says Ratey. "So having a workout will help focus, calming down, and impulsivity — it’s like taking a little bit of Prozac and a little bit of Ritalin."

Evidence mounts

Research showing a link between fitness and academics is growing. The California Department of Education (CDE) looked for a correlation between fitness scores and test scores. They found that kids who were deemed fit (by a standard test of aerobic capacity, BMI, abdominal strength, trunk strength, upper body strength and overall flexibility) scored twice as well on academic tests as those that were unfit. In the second year of the study, socio-economic status was taken into account, to possibly eliminate that variable as an explanation. As expected, those in the upper-income brackets scored better overall on the academic tests, but within the lower-income set of students, the same results were observed — kids who were more fit performed better academically.

Charles Hillman, associate professor of kinesiology at the University of Illinois, was able to duplicate these findings with 259 third and fifth-grade Illinois students. His team also noticed that two of the tests, BMI and aerobic capacity, were significantly more influential to higher academic scores than the other four fitness factors. Digging deeper, he isolated two groups of 20 students, one fit and the other unfit. They were given cognitive tests of attention, working memory and processing speed while their brain's electrical activity was being measured by an electroencephalogram (EEG) test.

The fit kids’ brains showed more activity in the prefrontal cortex, known for its executive function and control over other brain processes.

So, just send the kids on a fast jog and they will ace all of their tests? Not quite.

“The exercise itself doesn’t make you smarter, but it puts the brain of the learners in the optimal position for them to learn,” Ratey said. “There’s no way to say for sure that improves learning capacity for kids, but it certainly seems to correlate to that."

Please visit my other articles on Livescience.com

Related Stories:
Athletic Gene ACTN3 = "All Children Test Newborn To 3"?
Sideline Raging Soccer Moms (and Dads!)
Does Practice Make Perfect?