I wouldn't say it has nothing to do with genes. There is most definitely a genetic tendency for metabolic disorders like IRS. Science has even isolated markers which are common in people with IRS.

Still, people often think susceptability = fate. It doesn't. Even if you were born "allergic to carbs" because of what they do to you, that doesn't mean you are destined to grow fatter develop diabetes and eventually diet of a heart attack. Your choices will determine what happens. If you eat a low sugar diet you can prevent all that before it's too late.

My whole life I never could understand why I became hungry so much more quickly than everyone else, and why the way I experienced "hunger" seemed to be so much worse than others. I didn't understand why my hormones were all out of wack (by my late teens I had really bad PCOS). When I learned about hyperinsulinemia and the way food affects the body, I was able to choose health. Thankfully, I learned about what was wrong with me before I became really bad off (diabetic w/ heart disease).