To a certain extent, health is not genetic. A 2018 study of two 52-year-old identical twins revealed major health differences in the two men as a result of their lifestyle differences.
One of the twins, TT, regularly participated in various modes of endurance activity. He competed in multiple marathons and triathlons. The other twin, UT, didn’t engage in regular activity other than daily living. TT works as a high school track coach and UT is a truck driver.
The variables with the biggest difference between the twins were: body composition, VO2 max, grip strength, and leg strength–all of which are predictors of mortality.
The twins had fairly similar environments through development (birth through roughly age 20), and then very divergent lifestyles from ages 20 through 50. “The purpose of this study was to explore the effects of 30 years of endurance training on skeletal muscle health and physiological performance in these twins.”
The study found extreme differences in the body composition of the two twins. TT exhibited lower total body mass and percentage of body fat, lower resting heart rate and cholesterol, and higher aerobic capacity (VO2 Max).
"suggest the cardiovascular and skeletal muscle systems exhibit greater plasticity than previously thought…"
— Timothy Caulfield (@CaulfieldTim) September 25, 2018
The difference in body composition is not entirely dependent on exercise, the authors found several lifestyle factors that contributed to the twin’s differences. “Short term dietary tracking indicated that UT consumed 35 more kcals over his estimated total daily energy expenditure than TT. This small difference accounts for roughly seven kilograms of additional body mass when extrapolated over 30 years.”
UT had stronger grip strength, which could be a result of his delivery truck occupation but this remains speculative.
The authors conclude that, “Our findings support utilizing chronic endurance exercise training to improve body composition and cardiovascular health and suggest these physiological symptoms exhibit greater plasticity than previously thought.” The moral of the story is that exercise may be of even more benefit than researchers realized.