Some of the blogs we have posted such as What We Eat Impacts Our Genes, Not So Happy Meals and Good News for Extra Virgin Olive Oil Usersrefer to research showing that a person doesn't have to be held hostage by their genes. These and other research studies show that what a person eats influences how that person's genes express. This means that even if you have genes that cause obesity or being overweight, you can maintain a normal weight. It also means you can decrease your risk of the diseases associated with obesity or being overweight.

Now there is evidence that exercise can affect gene expression as well. Researchers at Washington University in St. Louis used PET scans to image the brains of 201 participants, ages 45-88, who tested normal on a test for cognitive decline. Next the researchers tested the participants for a variation of the APOE gene known as e4. The APOE gene provides instructions for making a specific type of lipoprotein called very low-density lipoprotein (VLDL). VLDLs remove excess cholesterol from the blood and carry it to the liver for processing. People with the e4 variation are 15 times more likely to develop Alzheimer’s compared with those who do not. People with the variant usually show signs of dementia at a younger age than people without the variant.

The e4 variant is found in 15 to 20 percent of the population. In this study, 52 people had the e4 variant. Among these 52, those who were sedentary had a greater buildup of amyloid plaques -- which are associated with the development of Alzheimer's -- than other participants in the group. The participants with the e4 variant who were physically active showed no more buildup of amyloid plaques than found in the brains of non-carriers. The scientists noted that the genetic risk "makes beneficial lifestyle factors, such as exercise, preferentially important."

John C. Morris, senior author of the study published stated, "While the study shows that those who exercised had fewer amyloid plaques in the brain, the signature markers of the disease, more follow up is needed to see if exercise actually delayed or blocked symptoms." One point of interest is whether beginning to exercise after plaques have started to build up might alter that outcome. Experiments with mice have shown that elderly animals benefited from beginning a running program and experienced less dementia than mice that didn’t run.

One important aspect of the research that deserves to be underscored is that an inactive lifestyle seemed to accelerate the accumulation of amyloid plaques. Those with the e4 variant who rarely or never exercised had the most plaques, putting them at heightened risk for the memory loss of Alzheimer’s in the years to come.

If you find that you have difficulty incorporating exercise into your life and you watch TV, you might want to consider walking during commercial breaks. A study from the University of Tennessee at Knoxville found that people who just stepped in place during commercial breaks burned an average of 148 calories during one hour of TV viewing. Walking in place during commercials will also help you lower your cancer risk as noted in my blog Don't Sit Still for This. Exercise really is worth the effort -- it changes your body at the cellular level in ways we have only begun to understand.