>The researchers were looking for young adult identical twins in their early- to mid-20s whose exercise habits had substantially diverged after they had left their childhood homes. These twins were not easy to find. Most of the pairs had maintained remarkably similar exercise routines, despite living apart.
And they also highlight that while the genetics and environment play a huge part they don't preclude change:
>More subtly, the findings also point out that genetics and environment “do not have to be” destiny when it comes to exercise habits, Dr. Kujala said. For these particular twins, whether their genes and childhoods nudged them toward exercising regularly or slumping on the couch, one of the pair overcame that legacy and did the opposite (for better and worse).
Being active is a choice (for most people). Certainly, some people are more likely to do it naturally, but that doesn't preclude the rest of us from doing it.
Maybe environmental concerns (eg: stress) impact your health and fitness indicators, which causes a lack of motivation and energy for exercise that you would normally have without the stress. I know, as an overweight and highly stressed person, that I often feel that way about exercise.
Your habits and lifestyle are basically pre-determined by a certain age but as the article shows, they are not set in stone because lifestyles may change.