Yay, I've wanted to answer this question for a while.
This is a question of epigenetic imprinting, and yes it is possible. Here's how it goes. We have DNA, everyone pretty much knows that. We are born with a combination of DNA from our mother and father. DNA tells our body how to grow and how to generate cells. What was recently discovered was that we have what is called epi-DNA or literally (above the DNA). It tells which parts of our genes to function and to what extent. While the DNA we were born with cannot change, our epigenetic functioning can change due to outside factors.
A study was done with mice. Soon to be mother mice, not yet mated, were separated into two groups. One group was given a healthy supplemented diet and the other was not. The mice were then impregnated and the offspring were very different. The ones with the unhealthy mother had lower glucose tolerance and a higher occurrence of cancer, they also had a yellow coat whereas the offspring of the healthy mother had darker brown coats. I'm not sure, but I believe the diets of the mother mice were the same while they were pregnant. So basically, what the mother ate before she was pregnant affected her offspring.
Another example of this is with identical twins. Identical twins have identical DNA, but their epiDNA is only identical shortly after they are conceived. Outside factors effect each of the twins epiDNA differently. A study was done on twin 4 year old boys and twin 74 year old women. The epiDNA of the 4 year olds was nearly identical while the epiDNA of the 74 year olds was very different. Different life experiences and health habits affected the twins in different ways. This is why sometimes one twin will end up taller or one will be more likely to get cancer. Lifestyle and habits actually change part of your genes.
So here's a warning, if you're planning on having children, but don't think your nasty habits like smoking, excessive drinking, drug use, unhealthy eating, or excessive stress will effect your future children as long as you don't do it when you're pregnant (If you're a woman), think again. If you are a man or a woman, anything that you do when you're young will effect your children. Fortunately, it doesn't have drastic effects. My grandmother smoked since about the age of 12 and during her pregnancy with my dad. I turned out fine, I think. It probably did have some tiny effect on me though
.
I think the opposite works too. If you're healthy and exercise, then those traits will probably be passed on too.
I'm no expert on this stuff, and there really isn't much out there about it yet. It's pretty new research. But it provides an alternative to the idea the natural selection is the only explanation for evolution. Natural selection really doesn't explain much these days since most of the population is able to procreate.
I hope that helped!
