Fitness fanatic or couch potato? Blame your DNA

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By Christie Aschwanden
September 8, 2009

For decades, fitness gurus have admonished sofa spuds to adopt a can-do attitude toward exercise, as if the only thing keeping them from the gym or walking path was the right attitude.

Yet a growing body of evidence suggests that it’s not merely motivation but also genetics that separate slouches from fitness fanatics, and at least some of these genes appear to act on the brain’s pleasure and reward center.

Though the science doesn’t imply that people disinclined to exercise can’t get moving, it helps explain why some people find it more difficult than others to “just do it.”

“We all know people who can’t sit still and we all know people who can’t get off the couch,” says J. Timothy Lightfoot, an exercise physiologist at the University of North Carolina in Charlotte.

Studies of twins suggest that some of the differences between these types of people come down to genetics. A 2006 Swedish investigation looked at leisure-time physical activity in 5,334 identical and 8,028 fraternal twins. The findings revealed that the exercise habits of identical twins were twice as closely matched as those of fraternal twins.

Fraternal twins share half their genes on average, whereas identical twins are genetic duplicates, so the finding implies that genes account for much of the variability in physical activity levels between people.

Likewise, a 2006 study that pooled data on exercise participation in more than 37,000 twin pairs from seven European countries calculated the genetic influence on physical activity at somewhere between 48% and 71%.

And these are not isolated findings.

“We now have more than 20 twin studies showing almost unanimously that [identical] twins are more alike in their physical activity than [fraternal] twins,” says geneticist Claude Bouchard, executive director of the Pennington Biomedical Research Center in Baton Rouge, La. The studies make a compelling case that the inclination to exercise runs in families, he says.

Studying mice
In an effort to find the genes involved, physiologist Theodore Garland at UC Riverside turned to rodents. He placed exercise wheels in the cages of ordinary mice and measured how often they scurried around in the wheels.

“This was voluntary exercise,” Garland says. “It’s sort of like how some people jog and others don’t.”

Researchers then selected the mice who ran the most and bred them with other so-called “high-runners” and repeated the experiment for more than 50 generations.

The result was a strain of high-runner mice that run as many as eight hours per night.

Garland’s next step was to find out what caused the mice to want to run. He found clues in the brain.

In a study published in 2003, his group showed that high-runner mice and regular mice respond differently to stimulants such as cocaine and Ritalin. Regular mice would run more when plied with the stimulants. “But we’ve never found a drug that will increase running in high-running mice,” he says. Whatever those drugs do in the brain seemed to be already turned on in the high-runner mice.

Because cocaine and Ritalin alter levels of the brain chemical dopamine, a neurotransmitter involved in pleasure and reward, the drugs’ different effects on the two breeds suggest high-runner and regular mice may process dopamine differently in the brain — and that may dictate how much pleasure they get out of running.

Other studies have also linked physical activity to dopamine.

For instance, a 1998 study showed that mice deficient in a receptor involved in processing dopamine, the D2 receptor, are less active than those with normal D2 receptor levels.

More recently, Lightfoot and his colleague Amy Knab found that two other dopamine-related genes were less active in their high-runner mice.
Says Knab, who is an exercise physiologist at Appalachian State University, “There’s something inherently different in the dopamine systems of the high-runners versus low-runners.”

Human studies have also linked exercise frequency to dopamine. Bouchard’s research team studied physical activity levels in a sample of 721 volunteers from 161 families in Quebec, Canada. They found that variations in the dopamine D2 receptor gene correlated to physical activity levels in women, but not men.

It’s a start
Bouchard says the study is an intriguing start — but he speculates that there are many more genes that influence exercise inclination.

Environment still plays a major role in how much someone exercises, though. “You can’t blame being lazy on your genes,” Knab says.

In fact, a twins study published last year suggests that environment trumps genetics when it comes to the kind of exercise needed for good health.

When University of Washington exercise physiologist Glen Duncan and his colleagues examined data from the university’s twin registry they found that genetics did predict the propensity to exercise up to 60 minutes per week.

But at 150 minutes or more — the amount of exercise that public health officials recommend — “the genetic component went away and the environment was the bigger factor,” Duncan says. For example, if people walk into a building and see a set of stairs first thing, they will probably take them. But if there’s an escalator front and center, they’ll take that instead, he says.

Researchers are now trying to tease out the ways that genes and the environment combine to turn one person into a marathon runner and another into a couch potato. By doing so, they may discover more effective ways to encourage exercise among those not naturally inclined.

“It’s really hard to change people’s physical activity levels,” physiologist Joey Eisenmann at Michigan State University says.

“There are a lot of people working on interventions to increase physical activity, and for the most part they haven’t been shown to be highly effective. As we learn more about genetic factors, that may shed light on why these programs don’t work as well as we’d like.”

Some of this research may eventually lead to more individualized approaches to fitness.

Or — failing that — researchers may even learn to enhance exercise’s gratifying effects with drugs.

“Some day,” Garland says, “we could be giving people pills to make it more pleasurable to run.”

Keep the Cup

The Fill Your Cup lifestyle is a maturation process. Learning to eat less is so simple, but changing a habit is rarely a linear progression. We remind, revisit, and come to a deeper understanding of how to fill ourselves emotionally and nutritionally.

The Fill Your Cup Lifestyle is just like life, a few setbacks, re-directions, goal alignments, and a deeper awareness of what you really feel. You may fall away from your goal and then come back into it. No worries just re-connect and feel the difference.

As you practice filling only your cup – the cup of your two hands, three times every day – it gets easier. “Practice makes perfect” as the adage goes. Stay hungry, never stuff your belly, and become accustomed to that feeling of space. But, this is your sensory, emotional, exploratory life – enjoy it! Eat exactly what you want to eat and fully savor those few bites.

Fill Your Cup is about being truly satisfied with exactly what you want to eat rather than stuffing your self with something you (reluctantly) accept as good for you. Stay 20% hungry and let that that discomfort disappears in the joy and love of your life. Then, you will get the bonus of feeling great in your own skin. Have a wonderful week – Fill Your Cup!

Right or Easy

“Soon we must all make a choice between what is right and what is easy” Professor Dumbledore – Harry Potter Goblet of Fire

Food is just too easy. It’s literally on every street corner and compared to our incomes in this country – it is cheap to buy. It is also tasty – it has to be for capitalism to thrive. After all there is competition for the food vendors on every corner. Their offering must be bigger, tastier, more addictive, enticing and inexpensive than the vendor next door.

Eating plenty is easy – eating less (and fresh, whole and well) is right. You get choices every day – which will you chose? Fill your cup.

Mother – Thanks

In the Book Fill My Cup I thank my mother for her early training it weight management. She would say, “Nothing tastes as good as thin feels…”
Today’s mothers fear an assortment of eating disorders (that apparently my mother didn’t consider with me) and would probably never say such a thing.

Then funny thing, today Mom and I were having lunch at the Mandala Tea room (An enchanting spot in Scottsdale, AZ an organic, vegan and raw food connoisseur’s delight.) and a really really thin young woman walked in and my mom immediately commented, “Now that girl has anorexia!” I was shocked at my Mom; apparently she has limits to applauding thin-ness. In our society of over indulgences and decadence typically, lightening the cup is the way to go. Longevity research shows with out a doubt that staying a little hungry and limiting calories, increases our life span. Occasionally, filling the cup the best way we can is a laborious task and skipping meals is easier. Yet, not getting adequate calories to sustain your lifestyle can be as unhealthy as over indulging.

Fill your cup as a proportional portion to your body size. Some days may be lighter or heavier for sure, but love your body and fuel it for energy, clarity, and light.

My mother guided my instincts as nurse and self-educated nutritionist. (She still takes vegetarian and vegan cooking classes.) Yet, I have learned from real life experience that everyone has to find their own way with food, and feel what they are hungry for to sustain their body.

My goals with Fill my Cup are:
To guide you to your own knowing of what you “should” eat;
To provide a container for your experience as well as your meals (the cup of your two hands;)
To foster your happiness with how your body looks and feels.

You need fantastic energy sources for the lifestyle you desire. Find your clarity, it’s your body, your life, your path to wellness and peace. Eat what you know you should; just keep it in the cup! Much love this Mother’s Day, Julie

Mind/Body

It takes a mind body connection at the very depths of your psyche to fill your cup ALL of the time.

Even though Fill my Cup is my concept; and being in the cup 80% of the time keeps me happy and in my skinny jeans – everyday life can bump me off track. Our accountability through twitter and in mind body exercise certainly motivates me, yet I am still not connected ALL of the time, … at least not yet.

Sometimes the requirements of my life, kids, their school, sports etc… force me into a race where I show up with the best habits I have, but slip into “auto pilot” to get through the day. It’s a day where my breath is short, and then so is my temper. My posture stays in static resignation. I have tension under my skin and I don’t even know it until I try to touch my toes. I make an effort to stay present in conversation but beyond that, the humanity that touches my life floats past me as I muddle through a list.

That was last week.

This week I reconnect. My body moves like a stranger. I don’t know or like it. I feed it out of habit but still cant feel its requirements as well as I like to. I walk, bathe, read, and feel. I tickle my kids, laugh, teach Pilates, go to yoga, teach spin and finally I am coming back in … step-by-step, poco a poco, (little by little)…. are those my ribs expanding as I breathe?

Maybe tomorrow I can shop for food. I need something raw and fresh and grounding.

2 of 3 ways to combat hunger and stay in tune with your body

“Cup” Friends:  It’s fun to have an exercise buddy that supports your goals and provides camaraderie for your new exercise and eating program. Friends with like values, make great exercise partners.   You may also pick similar restaurants or bars to visit if your friends enjoy the same foods that you do.  I have friends that I ride with in my cycle classes and there is an amazing feel in the room with the synergy we create in a pack.  I have other friends that I meet for yoga classes and we meet at a slightly different but no less synergistic place.  I also have some friends who I hang out with socially but who are also conscious of what they eat and drink.   We never order giant portions or extra deserts; we just have fun being together.  I have a client who was doing really great with her commitment to exercise and adjusting her values about diet to meet her goals.  She told me that her friends and relatives seem to try to sabotage her efforts.  They were offering her foods she did not plan to eat and inviting her out to lunch when she was on her way to the gym.    Some relationships are undermining; they are a leak of your energy.   You need all the energy you can get while making profound changes in your body and your relationship to food.  Keep anyone who is not supportive at arms length for your first few months.  Choosing friends who support your goals is a conscious choice, just like the conscious choices you make about what you put in your Cup!

If you are married or in a long term relationship try to make your Cup-diet changes a joint commitment.  If you are trying to clear the snack foods and your partner keeps bringing them back into your sight it will be really difficult to stay on track.  When you are happier in your body you will be happier close to their body.  It is really good for both of you when you feel connected to your body.