You know that friend who can eat anything she wants and not gain weight? Meanwhile, you eat all the right things and yet can never seem to lose weight, at least not for long? Sometimes you think: I feel like the deck is stacked against me, and it's not my fault. I have a slow metabolism. I was born this way. Well, now it turns out you may be right! There is a so-called fat gene–or a variant on chromosome 16–that in part determines who has a harder time maintaining a healthy weight from the fear they learn to feed themselves. But the mechanism may not be what you think. It's not simply that some people torch calories and others burn like a candle. It's subtler than that, and this gene shows us that there are ways to learn to eat to short circuit your hardwiring. One doctor has advice on how he beat it and you can too.

"Your genes load the gun. Lifestyle pulls the trigger" says Dr. Joel Kahn, cardiologist and long-time plant-based eater who himself found out that he has the genetic variant that makes it easier to put on weight and harder to keep it off. Kahn, the author of The Whole Heart Solution, has eaten a plant-based diet since he was 18, and credits this healthy plant-based approach (long on vegetables, short on fat and sugars) with keeping his weight under control.

"I will never be gaunt like some of my colleagues who eat this way,"  he says. "But I wore a husky suit to my bar mitzvah, and I knew I would have to change my diet." Kahn went plant-based at 18, but by that time he says he had already figured out how to manage his portion control and stay trim. Eating plant-based for 40 years has been the key to life-long health and maintaining a healthy weight.

Dr. Kahn has not only learned how to eat healthy personally but made it his life's work to help others do so as well. He is the founder of the Kahn Center for Cardiac Longevity in Bingham Farms, Michigan, a Clinical Professor of Medicine at Wayne State University School of Medicine, and a bestselling author.

What does the "fat gene" variant do, and can you counteract it?

"The proper name of the gene is the FTO gene, a small snippet on chromosome 16, which stands for Fat Mass and Obesity," Kahn explained. A study of schoolchildren found out that the genetic variant does not affect how your body handles calories, but it does drive up how much you are likely to eat.

They identified school children who had the FTO gene and offered them meals that had been measured and weighed to see if they ate more. Indeed, the students with the gene were likely to take in more calories at every meal than those without it. This is good news for anyone who has the FTO variant since it does not impact your metabolism, but is linked to eating more food, especially high-calorie food, the study found.

"The FTO variant seemed to be involved in the consumption of calories, not how the body handles those calories," according to the study authors.

The FTO gene appears to regulate ghrelin, a hormone that tells your body to eat more. if you eat a meal and ghrelin is still present, then the brain never gets the signal to stop eating. FTO may make ghrelin stick around longer for people who have the variant than people for those without it. For most people, since this is something they have had since birth, they learn to pay closer attention to their satiety cues and have to teach themselves when to stop.

How do you find out if you have the fat gene, aka the FTO variant?

To find out if you have the FTO variant on chromosome 16, you can pay for a genetic testing profile such as 23andMe or MaxGen, Kahn explains. He found out because he is in a genetic testing group, which has told him more about his health than most people learn without that.

If you have the variant, don't go yell at your parents for being the ones who handed this down to you (chances are at least one of them has struggled with their weight in their lives, after all). The good news is there is something you can do about it. You can begin by spending more time in the produce aisle, shopping for whole plant-based foods, and eating a nutrient-dense diet, makes it easier to feel full and not over-eat, which you are more likely to do with calorie-dense foods like sweets and junk food.

If you don't have a pronounced hunger cue that tells you to switch off eating, then choosing foods high in fiber, that are filling, nutrient-dense will make it easier to control your weight and still be satisfied. And most people with FTO tend to overdo the high-calorie foods, which researchers believe may finally quell their runaway appetite. So choosing a whole food plant-based diet will also help you stay away from processed foods, Kahn explains.

DNA is the one thing you can't change. Lifestyle habits have a bigger impact

Instead of crying about the fact that you may have this lack of a turn-off switch when you sit down to eat, think of all the good things in your DNA: Your creativity and intelligence, sense of humor, your strong arms, loving smile, great hair. And instead of trying fad diet after fad diet, simply ditch the short-term diets (which generally don't work) and start to eat a clean, whole-food, plant-based diet, rich in vegetables and grains, fruit and nuts, seeds, and anything that would ordinarily grow in the ground. You'll end up eating healthier than 90 percent of the rest of Americans, who don't get their five servings of fruits and vegetables a day.

A study of school children showed those with the genetic variant ate more

In a study by the Early Growth Genetics Consortium (EGGC) that looked at 20,000 individuals of European descent, babies under two with the gene don't show any significant difference in BMI from the rest of the population, but once a child is old enough to feed itself and not have the normal satiety cues, their BMI goes up, so that by six years of age there is a difference in BMI compared to those who don't have the variant.

The study showed that this can have an effect on their ability to maintain a healthy weight unless they learn to curb their appetite and listen to the subtle satiety cues. That's also good news for all of us since it shows that if teenagers with the genetic variant can learn to curb their appetite for high-calorie foods, we can too.

Eating a plant-based diet can be a game-changer, since it makes you feel full

"I never was the kid who could win the 50-yard dash in school," Kahn explains. He jokes that he was so slow some people think he is still running it. If this is something you can relate to, then going plant-based could be the right choice to help you eat enough to feel full and satisfied but fill up on nutrient-dense foods like fruits and vegetables. "For some people, your BMI will never be that low. But I have kept mine in the normal range by eating this way my whole life." Still, it helps to know your genetics and your family history, he explains. He found out he got the FTO gene from both parents, so it's been a life of eating right to keep that variant from winning.

"People who eat plant-based will tell you that a no oil, no sugar diet will be bulletproof," Kahn says. But even then you can also get unlucky with a gene for high cholesterol, so while this is a healthy way to eat, he adds, you still need to see your doctor if you don't know your family history. "If you eat a whole food plant-based diet, you will be NEARLY bulletproof.," he adds.

Even going plant-based, you have to watch your food choices, Kahn adds since "vegan" in itself is not synonymous with healthy. "You can eat vegan and still eat too much or load up on sugar. The environment has also changed since I was a kid," Kahn says, "and now there are plastic phthalates and other chemicals in foods that were simply not there when I was a kid."

Plus he explains, our stressors like constantly being on our phones and screens contribute to our getting less sleep, which further drives up ghrelin. So if you have this genetic variant, do try to get more sleep, Kahn suggests. "There's data about how we sleep less than 30 or 40 years ago. All those pressures have an effect on our diet and our health. And that's why genetics might be more important."

The term precision medicine or personalized medicine is making its way into health care, Kahn says. "We are still a bit away from practicing medicine based on genetics," in which doctors treat patients differently depending on their DNA.

Until then, eat healthily, get sleep, and be nice to your parents.