By Gabe Mirkin, MD
Studies in the new field of Epigenetics are showing that lifestyle factors can change the way your body responds to your genes. In one of these studies, researchers were delighted to find a set of identical twins with vastly different lifestyles. They found that a lifetime of exercise is likely to give you the body characteristics of a healthy athlete, while an inactive lifestyle can give you body characteristics associated with increased risk for many diseases (Eur J Appl Physiol, July 14, 2018).
• The first twin is a 52-year-old endurance athlete who trains and competes regularly in marathons and triathlons. He ran 39,431 miles over the last 22 years, which is an average of 1,792 miles per year or 34.5 miles per week. He also has a very active job as a high school track coach. This twin ran track and cross-country in high school and college, and then began running marathons and competing in triathlons from his thirties onward.
• The second twin is a 52-year-old truck driver whose job requires a lot of sitting. He had played recreational baseball and basketball from ages 10 to 20, and continued to cycle and play basketball occasionally until age 39, when he injured his ankle and stopped exercising completely.
Health measures: At age 52, the training twin had a 30 percent lower resting heart rate, lower blood pressure, lower cholesterol, lower fasting blood sugar, lower body fat, lower triglycerides and greater aerobic capacity and endurance. His maximal ability to take in and use oxygen (VO2 max) was equal to that of a fit 30-year old. The training twin also had 55 percent more “slow-twitch” muscle fibers than the non-training twin, meaning that he could run for hours without getting fatigued.
Weight: The non-training twin weighed 22 pounds more than the training twin, with virtually all of the extra weight in the form of fat.
Muscle: Enhanced X ray scans showed that they both had the same total amount of muscle, but the training twin had 94 percent slow-twitch fibers while the non-training twin had only 40 percent slow-twitch fibers. Slow-twitch fibers enhance endurance, while fast-twitch fibers give you strength. This suggests that a lifetime of running converted most of the training twin’s muscle fibers to those that govern endurance, and that lack of exercise does not promote the growth of slow-twitch endurance type fibers. Surprisingly, the non-training twin had stronger legs than the training twin, which probably means that the constant leg fatigue from many miles of running interfered with extra growth and conversion to strength-type fibers. This can explain why endurance athletes such as long-distance runners, cyclists and cross country skiers do not have very large muscles in spite of the many hours they exercise each day.
Athletic performance: The training twin had far greater relative cycling power, endurance and maximal ability to take in and use oxygen (VO2max), while the non-training twin had more leg press strength, larger muscles and a greater percentage of strength fibers in his muscles. The training twin also had higher levels of the enzymes that govern endurance and the use of oxygen.
A similar study on another set of identical twins showed that compared to the heavier twin, the lighter twin spent 30 percent more time in moderate physical activity, took 21 percent more steps per day, had a 14 percent greater maximal ability to take in and use oxygen and 8.6 percent lower body fat (Scand J Med Sci Sports, Mar 2018;28(3):1048-1055).
What is Epigenetics?
The term epigenetics means “above” genetics, the external modifications to DNA that turn genes on or off. You inherit your genes from your parents, but many factors during your lifetime can turn your more than 20,000 genes off or on. You can change the way that your body responds to your genes by what you eat, whether you exercise, whether you are overweight, if you are exposed to various chemicals, where you live, with whom you associate and so forth. Also, certain diseases can cause your body to respond in a way that is opposite to its intended direction. For example, normal genes direct cells to live only a limited number of doublings. Factors that lead to cancer can cause the cells to try to live forever, so the cancerous cells become so numerous that they can kill you by crowding out and destroying other tissues.
The good news is that any gene that is turned off should theoretically be able to be turned on by a different environmental factor. For example, we should be able to cure cancer just by finding a factor that turns on the genes to keep cancerous cells from trying to live forever. We should be able to cure obesity by turning on the genes that keep us from storing excess fat.
Hundreds of scientific papers in this exciting new field of Epigenetics are showing that you can change the ways your body responds to your genes just by changing your lifestyle. This research is showing that you can improve your health and prolong your life by trying to:
• exercise every day
• work actively to control excess weight
• eat a healthful, primarily plant-based diet that includes a variety of vegetables, fruits, nuts, whole grains, beans and other seeds
• avoid smoke
• restrict alcohol
• avoid industrial chemicals and pollutants that are known to be harmful