CHAPTER 1 Why You Should Eat for Your Very Own Genes The first and most important genetic self-test that I''m going to introduce you to is an incredibly powerful tool that will allow you to individualize your carbohydrate intake levels. The results of this first self-test will help you find out which one of three carbohydrate consumption categories you fall into. Until recently it was assumed that we all inherited a copy of each gene, one from each parent. And that''s why it was thought that you have two copies of every gene. Oh, how wrong we were. It turns out that some of us have a little more or less DNA than others. And far from being insignificant, the number of copies of genes you''ve inherited can have a tremendous impact on your life and health. To get more nutritional horsepower out of your genome, for example, an ancestor of yours might have gifted you with multiple copies of a certain gene.

Instead of the usual two copies of a gene, you may have inherited even a dozen copies or more. The technical term for this phenomenon is copy number variation, or CNV, and it seems that this has happened at many different times and places in our evolutionary history.1 We all vary in the number of some of the genes that we have inherited--even within the same family. Okay, so why should you care today how many copies of a gene you may have inherited from a specific ancestor thousands of years ago? Because many of these variations in the number of specific genes you''ve inherited were passed on from your ancestors as an advantage when eating certain things for breakfast, lunch, or dinner. That dietary advantage for the specific nutritional environment would then be passed on and maintained down a specific genetic ancestral line. And as you''re going to discover yourself, the copy number of certain genes you inherit plays a very important role in determining your optimal diet today. Using this information, you can follow an individualized diet that will help you get to and stay at your ideal weight, painlessly. And most importantly, it will do this while improving your overall health and increasing your genetic longevity.

You''ll gain all of these benefits simply because you understand your unique CNV when it comes to certain genes and how that should dictate your dietary choices. See why you should care? That''s why for the most part doing what others do when it comes to diet and lifestyle may be perfectly fine for them, but over a lifetime of bad genetic decision making, the consequences can even turn deadly for you. Since the first complete draft of the human genome was published back in 2001, we are becoming more aware that the most striking and impactful genetic differences between us are actually found in genes that impact our diet. The way our bodies digest and use energy from the food we eat depends more upon what your recent genetic ancestors ate than we ever imagined. And these genetic differences can have an incredibly powerful influence on not just our basic nutritional needs but also on the amount of carbohydrates we can eat, down to the ability for us to either thrive or wilt upon consuming a large amount of protein. To illustrate the importance of how genetic differences between people can affect what they should be eating, I have often asked my patients what type of fuel they use to power their cars. Here''s why: Some makes and models require a high-grade gasoline while others can get by with the lowest and cheapest type around. Others even require a special type of fuel such as diesel or propane, while some cars are now powered by electricity alone.

When it comes to your car, you find out which type of fuel to use by consulting your vehicle''s owner''s manual. Now you might think that we weren''t born with a similar type of instructional manual. Or worse, you think or have been told that a manual like that might exist and that it would be applicable to all of us. In fact, what you have within you is incredibly more detailed and impressively individualized. I''m talking about a three-billion-letter genetic code that is full of individualized and unique wisdom that was collected and annotated over millennia just for you. Every nutritional adaptation that allowed your genetic ancestor to survive long enough to pass on that knowledge to his or her own children is in there--a veritable genetic tapestry gifted to you from every direct genetic ancestor you have ever had. That tapestry, when it''s spread out, is very, very large: about three billion genetic letters or nucleotides'' worth making up your genome. And you actually have two genomes--one from your mother and one from your father, which is why you''re not identical to either one.

Within our genomes we also each have somewhere in the ballpark of 20,000 genes that do most of the genetic heavy lifting in our bodies. Nearly every single one of your trillion cells has an entire copy of your genome inside it.2 That''s how the folks on CSI were able to identify people with only a very small sample of hair or tissue. Most of the knowledge within your own DNA is on genetic autopilot, requiring little conscious input from you as your cells use it on a moment- to-moment basis to keep you alive. But if you really want to start to eat for your genes, you''re going to have to learn to speak their language. That''s why I''ve devised a few crucial at-home self-tests in the DNA Restart that will help you start decoding your own unique genetic inheritance. This information is required so that you can eat for a better, longer, healthier life. I''ve also included a few case studies of patients and colleagues to illustrate the power of what can happen when you finally start to eat for your own genes and stop eating for everyone else''s.

This is your life. Let''s get you started on your way to eating for your genes. 1You can learn more about the impact that CNVs can have on your health by reading one of my previous books, Inheritance: How Our Genes Change Our Lives--and Our Lives Change Our Genes. 2The only cells that don''t have DNA are mature red blood cells. They actually got rid of their DNA to make more room so they could pack themselves full of more hemoglobin.