"You are stuck with the genes that you had from birth." Have you ever heard that? Is it a true statement, or can we influence and possibly improve our genes based on our lifestyle choices -- such as nutrition, exercise and healthy behaviors? I interviewed Dr. Cate Shanahan about a few of these topics to see if we have more control than we think and her answers solved many misconceptions about genes and behavior.
Brief bio:

Dr. Cate Shanahan is a board certified Family Physician. She trained in genetics and biochemistry at Cornell University before attending Robert Wood Johnson Medical School. She practiced in Hawaii for ten years where she studied ethnobotany and her healthiest patient’s culinary habits. She has published 2 books: "Deep Nutrition: Why Your Genes Need Traditional Food" and "Food Rules: A Doctor's Guide to Healthy Eating." When not writing or working, she can be usually found on the nearest mountain biking trail. Learn more at her website.
Genes play a major role in health and our lives, as we are born with these genes and "stuck with them" in a way. Can genes be influenced by our behavior -- such as eating healthier and exercising more often?

It's natural to worry about problems that run in your family and my patients often worry because "My mother was just diagnosed with breast cancer," "My dad had a heart attack at 45," "My grandmother has Alzheimers'." I explain that, contrary to popular medical mythology, which places family history in the "unmodifiable risk factor" column, there IS something you can do to improve the health of your genes.
Our genes are changing constantly. Everything we eat, drink, breathe, and do will affect their behavior and can physically alter the chromosomes in ways that can ultimately rewrite parts of the letter code for future generations. In that sense we are all guardians of our family DNA. This means that, just as an irresponsible debutant can squander his family inheritance, or the opposite -- a few smart business moves can greatly enrich a family's wealth -- we are the authors of our own family history and have as much control over our health as our parents did.
If your parents got sick early in life, whatever illnesses afflicted them are the illnesses most likely to affect you--if you eat the way they did. This is why certain diseases tend to run in families. But just because your parents developed metabolic imbalance that led to their own illnesses doesn't necessarily doom you to the same fate. No matter your age or your family history, no matter what your current metabolic impairments, your genes are ready to do their part in reviving your metabolism as soon as you get serious about a healthy lifestyle. The improvements in your metabolism won't necessarily happen overnight or in one smooth continuous progression, but every day you can make the wiser choices will be a good day -- one that edges your metabolism and your genes towards optimal function.

Editor's Note:
Recall the interview with Dan Eisenberg about telomere length and age of fathers and remember his advice about telomere length: "don't eat too much, eat healthy food and exercise."
What would be some good general guidelines to follow as far as fat and protein consumption?
I'm glad you asked this question because everyone asks this question in attempt to start defining a healthy diet and it's the wrong place to start. I can't tell you how much protein you need because the protein you get from sushi, for instance, is entirely more valuable to your body than any protein you might get from something like whey powder or tofu. I can't tell you how much fat you need because that depends entirely on what kind of fats we're talking about.
We need to start instead by defining what we mean by food. Our definition should not include the words, "protein, carbs, and fat."
Dietitians and nutritionists have trained us all to talk about food in reductionist terms and now health books pretty much only use these terms. Better that our discussion about healthy eating begin using the language of farmers, ranchers and chefs--the people who have been nourishing us all along (up until the past 150 or so years). We got into the mess we're in with rampant obesity and chronic disease partly because we stopped using terms like "good soil" "fresh" and "wild" and started describing foods as "carbohydrate," "fat," or "protein." These words fool people into buying empty calories and unnatural, harmful chemicals that are likely to promote metabolic derangements leading to hormone problems, inflammatory diseases, and more.
Luke and I wrote "Deep Nutrition" to empower readers with the ability to constantly create and refine their own perfect diet. But to do that you need to completely revise the way you think about how to meet your body's needs for food. We advise doing away with calorie counting and struggling to find the perfect ratio of carbs to protein to fat. These terms aren’t useful because they say nothing about what really matters to your body. The following definition of food comes from from the introduction to "Deep Nutrition":
Food is like a language, an unbroken information stream that connects every cell in your body to an aspect of the natural world. The better the source and the more undamaged the message when it arrives to your cells, the better your health will be. If you eat a properly cooked steak from an open-range, grass-fed cow, then you are receiving information not only about the health of that cow’s body, but about the health of the grasses from which it ate, and the soil from which those grasses grew. If you want to know whether or not a steak, or a fish, or a carrot is good for you, ask yourself what portions of the natural world it represents, and whether or not the bulk of that information remains intact. This requires traveling backwards down the food chain, step by step, until you reach the ground or the sea.
Make sure you know how to recognize processed foods disguised as health foods so you can avoid them completely--at least that's the ultimate goal. I'll talk about this at Sean Croxton's Real Food Summit.
So how should you portion out your foods?
The most important thing to do is limit your sweet tasting foods to a couple of bites or sips per day. Go for intensely flavored foods as often as you can. Don't follow any arbitrary rules like "eat every three hours" or "don't eat just before bed."
You can read the full interview here.