Genes do play a roll. My grandmother drank , smoked and lived life to the fullest. She died at 93. Cats can live longer than dogs. The people I work for have one that is 24. Science Diet, like alot of commercial foods. Contain By-products and grain. The grain is used to keep the meat parts together. All this during the manufacturing process is heated at high tempeture. Which destroys most of the nutrients.This maybe a bit off topic. I have three cats. No dog yet. Still doing research. My cats eat a mix of Science Diet R/D for weight loss. And Wellness Complete Health. This product contains Deboned chicken as its first ingredient. No grains or fillers. My small female eats Wellness Super mix. She doesn't need to lose weight at ten pounds. Ive tried to substitute Orijen. When you open the bag. Its smells like real food. This product contains 75% meat and fish and vegetables.Cooked at low tempeture. No grains. My large male cat, which is the size of a Cocker Spaniel. His weight is is over 29lbs. His target weight is 25lbs. I tried to just give him the Wellness . He had loose stools.So I mixed the food up. He and the smaller male (which is my avatar) Did not like the Orijen. I learned about this food from this forum. Here is their info: http://www.championpetfoods.com/orijen/orijen/ The female eats the Orijen. its a high quality food. Then are many good foods. Just do your research. Richard :D