How do nature and nurture interact to shape a persons life?

I do not think that it is possible to disagree with the
idea that both "nature" and "nurture" shape a person's
life.

Let us look at something like a person's weight. 
Clearly, some people are more predisposed than others to be heavy.  This is a way in
which nature shapes the person's life.  However, the person's upbringing (the "nurture"
aspect) clearly has an impact in this area.  A person who grows up in a family that goes
out for unhealthy, fast food meals all the time will surely be more likely to become
heavy than a person who lives in a family that eats in a healthy way.  The person may
still be heavy in the healthy family, but their "nurture" will have an impact on how
much their natural tendency to heaviness is actually manifested.