About 20 years ago, while I was teaching English to a smart section of eighth graders, we read an article about the unwanted byproducts of yo-yo dieting: an increase in body fat percentage and a decrease in muscle mass. One question led to another, and before I knew it, we were discussing genetics.

Now I've never been one to fill students with false hopes. While I might encourage a student by saying, "You can do many things," I will not say, "You can do anything" simply because it isn't true.

For instance, I don't care how much he loves horses, how hard he's willing to work out, or how stringent a diet he's willing to go on. There's no way I'm telling the broad-shouldered eighth grade boy who already weighs 180 pounds that he can become a jockey.

So after I stressed to the class that you can make dramatic changes to your body shape through diet and exercise, I added a caveat: that without intervention most of us are genetically predisposed to develop a body shape like mom or dad or a combination of both.

The bell rang and the class left, except for one girl who put her head on the desk. By the time I reached her seat, she was crying forcefully.

I asked her what the matter was, but she was hyperventilating to such a degree that I couldn't understand her response. Then she sat up, shook uncontrollably, and gasped it out again.

"I . . . don't want . . . to . . . look, look, look . . . like my mom."

If only the girl would've paid better attention to the entire explanation, maybe she wouldn't have cried like that. Anyway, I spent the next 10 minutes explaining how bad genetics can successfully be battled.

The woman who's self-conscious about the size of her hips, I told her, can always reduce their size somewhat, but there's no need for the transformation to end there. By increasing the width of her shoulders through weightlifting, the woman can create more of an hourglass figure and make those three inches lost from the hips appear to be a couple more.

I believe I showed before-and-after photos of a woman who had done just that to the girl before I sent her to her next class. Back then, before-and-after photos were the best proof that individuals could battle genetics.

Today, new research suggests that you can exert even greater control than body shape on bad genetics: that the right diet can stave off the specific diseases that run in your family.

The concept is called the epigenetic diet, and research done at the University of Alabama at Birmingham showed that eating a certain way can actually suppress genes from expressing themselves.

That's because there are components in certain foods that repress certain gene aberrations that create diseases. After UAB researchers identified a number of these disease-fighting compounds in vegetables in their labs, they reviewed similar studies done internationally.

The result was an article published this spring in the journal Clinical Epigenetics that declared certain foods can prevent certain diseases including cancer.

This is not to say that eating these foods alters your DNA, but that ingesting the components in these foods determines whether your "bad" genes express themselves fully, somewhat, or not at all. Additionally, other factors, like your degree of exercise, whether you smoke, and your exposure to pollution, affect gene expression.

The foods that the UAB researchers found to battle bad genes are cabbage, cauliflower, kale, Brussels sprouts, soy beans, fava beans, grapes, green tea, and broccoli though chances are there dozens more.

Drinking three cups of green tea per day, for example, provides the same amount of protection that suppressed the gene that triggers breast cancer from expressing itself in lab mice. One cup of broccoli a day contains enough sulforaphane, a phytochemical found in some of the other listed foods also, to reduce the incidence of a number of cancers.

Additional work has been done on sulforaphane since the publication of the UAB findings. Oregon State University researchers placed mice on a high-sulforaphane diet and found it retarded prostate tumor growth. Prostate cancer is the most common cause of death from cancer in men over age 75 and the third most common cause of death from cancer in men of all ages.

"[Retardation of tumor growth] is always what you look for in cancer therapies," Dr. Emily Ho, associate professor at OSU, said in an online article posted on Life Extension.org, suggesting that prudent use of the aforementioned foods might not only keep diseases from occurring but also fight them once the disease exists.

While it's quite possible that not many or even none! of the nine aforementioned foods are your favorites, research like this should provide the impetus for you to experiment with these foods in your standard fare.

Fava beans, cabbage, and grapes, for instance, can be added to salads, kale can be steamed and eaten like spinach, and many meat substitutes feature soy. Brussels sprouts, broccoli, and cauliflower are traditionally steamed, but many people prefer roasting them with some spices and a bit of olive oil.