There are different environmental factors that can change the way your genes are expressed.
One example is dramatic weight gain in someone's father. "Morris found that none of the rat daughters developed a weight problem, which isn’t surprising given what we know about standard genetics. However, daughters of fat dads did develop health problems related to obesity."
They did not inherit his obesity, but they inherited his health risks even though they were at a healthy weight.
Another thing that could affect the epigenetics is a dramatic weight gain in the mother.
“The Agouti gene controls fur color and the feeling of fullness after eating. With the gene switched on, the baby mice grew into orange adults that could never eat enough to be satisfied.”
The mother started a high fat diet, and it ended up turning off a gene. The gene was still there, it just was not doing its normal activities. It even passed down to her children.
Differences in social environments can also change the epigenetics.
“The mother’s licking flipped switches on the baby’s gene that shapes how rats respond to stress — showing that the behavior of one animal can sculpt the epigenetic clay of another animal”
They were even able to change the differences it made epigenetically, proving that it really did affect the epigenetics,
How can this benefit us?
Changing the ways genes are expressed based on our environment is important because our environment changes all the time. We need to adapt to our environment. To do that we need to be able to change. This allows us to do this.