Obesity: genetics vs. environment?
February 9, 2008
I can’t believe researchers are still arguing about whether obesity is due to genetics or environment when it is so obvious that both are involved. The latest study compared identical with non-identical twins and concludes that genetics explains an astounding 77% of the difference in obesity. That percentage is enormous in biological terms and reason enough for skepticism. The accompanying editorial gives additional reasons. My take on this: of course genetics matters, but 25 years ago kids didn’t used to be so fat and rates of childhood diabetes (type 2) used to be much lower. Genetics cannot have changed much in the last 25 years. If the percentage attributable to genetics really is this high, it means that 77% of the population is susceptible to becoming obese if the environmental conditions so predispose, which they most certainly do these days. Your take?
You don’t have to get in a time machine and go back 25 years. Just come here to Japan. While waiting in line at the grocery store last night I looked around and could see 150 people, none of whom were fat.
Japanese are not radically genetically different than Americans, and Japanese in Japan are not genetically different than fat Japanese-Americans.
As you say, as the environment becomes more obesogenic, some who have a slight, latent tendency to be obese become obese, where in the past they wouldn’t have.
An important thing to keep in mind is that in the context of obesity, being “genetically” predisposed to the condition simply means that a combination of genetic factors makes you want to eat more food. The food makes you fat. Mere genes don’t make you fat. It’s not a genetic disease like Tay-Sachs, where the mere presence of the genes equals the disease.
Comment by Mark — February 9, 2008 @ 12:22 pm
Agree. After 20 years of hearing and seeing what patients choose to eat/drink/exercise, I agree that we manipulate the genetic picture with our environmental choices. I just don’t think there exists a human genetically programmed to remain normal size while eating 5000 junk-food calories a day (or more) and maintaining a sedentary lifestyle. Yet, many of my patients do this and still declare they have no idea why they keep gaining weight.
Also, I love to people-watch in the grocery store. I almost never see thin people/families with carts full of high-calorie food. They may have the occasional junk food, but not a cart full.
I frequently see families of obese individuals pushing carts full of highly processed high-calorie, high-fat, high-sugar food and the cart contains very little, if any, fresh veggies/fruit/fish/poultry.
These obervations make it hard for me to believe we have created a generation of genetically determined obese people.
I also have some patients in my practice who have seen the light and revised their self care habits now that they have a diagnosis of diabetes. Some of these patients have revised their diet and exercise choices, and the resulting weight loss, glucose control, blood pressure improvement, and lipid improvement reassure me that we can and will improve the obesity picture when people revise their choices.
Comment by Sheila — February 10, 2008 @ 3:22 am
Haven’t people’s perceptions of what constitutes food changed radically in the last few decades as well? It took a Crohn’s disease diagnosis, starting a food blog, and a lot of reading for me to begin to comprehend how skewed my perceptions are, and how little what I’ve been eating my whole life has to do with actual, real food. Yes, we were taught the food pyramid in school, but we also had lunches sponsored by McDonald’s and reading rewards sponsored by Pizza Hut– and there wasn’t much else available in my small town anyway. How can we expect people to make healthy choices when those choice (a) aren’t readily available, (b) are more expensive and (c) aren’t what people’s palates are accustomed to?
What frustrates me the most is that our food supply is organized to produce exactly such insanely disordered eating patterns, and then those who gain weight (perhaps because they are genetically wired to do so under certain nutritional conditions) are dehumanized and told they’re horrible people for ‘choosing’ to be fat. Nobody makes nutritional choices in a vacuum. We need to revise the choices people are given and the way we teach children about food if we’re to expect people to make healthy food choices.
Comment by Sarah Grey — February 10, 2008 @ 1:01 pm
My guess is that the major “gene” passed down from parent to child is the habit of unhealthy eating. Yes it is difficult to find safe and truly healthy options in the grocery store aisles but with some research and common sense, it’s not impossible. Unfortunately you cannot rely on what the FDA or food marketers claim to be safe. You have to figure it out for yourself. The food industry is a political nightmare. You can pretty much bet that if it’s been processed, canned, fortified, enriched, contains more than 5 ingredients, comes from a fast food outlet, etc…it will be unhealthy, lacking in nutrients in their original form, and sometimes quite toxic. I’ve just finished a bit of research for my own interest on MSG and the glutamate industry and posted some stuff on my blog. Looking for reasons behind the obesity epidemic? Signs point to MSG not genes.
Comment by Teresa — February 11, 2008 @ 7:51 am
I live in Japan, where MSG has been used for a century, and obesity is insignificant.
But Teresa’s comment was a nostalgic blast from the past! Most nutritional conspiracy theorists these days blame HFCS or trans fat.
Me, I think it’s fluoridated water, electric blankets, and the metric system.
Comment by Mark — February 11, 2008 @ 8:04 am
Well what I meant to say was that SOME signs point to MSG (it’s one of many culprits obviously - point being that our food supply leaves little to be desired in the way of truly nutritious value). Mark, I’d be curious to know what was in the grocery carts of all those skinny folks?
Is there much difference in the Japanese food supply as compared to America?
Comment by Teresa — February 11, 2008 @ 12:20 pm
Teresa, they just eat less food. As measured in calories. That’s all there is to it.
Obesity is not caused by nefarious ingredients or toxins (Japanese also eat a lot of mercury-filled large predator fish, as a matter of fact, which causes them no harm whatsoever).
Japanese are not health nuts. They eat a lot of sodium, and a third of their daily calories is refined carbs in the form of polished white rice. Raw vegetables, such as salads, are not a traditional part of the Japanese diet. But simply by not eating an excessive amount of calories they stay relatively healthy and live long lives.
There is a proverb, “Hara hachi-bun,” which means eat until you’re 80 percent full.
Comment by Mark — February 11, 2008 @ 12:32 pm
Mark, just wondering where you get your health statistics and info or if you are a trained health professional? I’m always looking for sources to back up information so that I can decide whether I can trust it or not. I am not a trained health professional. I am just reading various sites, blogs, publications and studies to try to sort out what’s what.
Comment by Teresa — February 11, 2008 @ 4:06 pm
Parents who do drugs have children who do drugs. Isn’t that how the commercial went?
If parents emphasize the importance of exercise and healthy eating through their actions of purchasing and preparing whole healthy foods as well as staying physically active, children are more likely to follow that lead. Same goes for the lead of not-so-healthy diet and lifestyle choices.
I doubt that genetics plays a big part in this area. If we blame obesity mostly on genetics, does this give people the power or control over their situation?
Comment by Daniel Ithaca,NY — February 11, 2008 @ 8:39 pm
For every overweight person I see with a cart full of high fat, high calorie foods, I also see another overweight person with a cart full of low calorie, “healthy” grain, low fat foods that all the experts advise. But invariably, the products are high in starch or sugar, or both, and are highly processed.
I never see anyone with a cart as full of high fat, high calorie foods as mine, no matter what their weight (though I know from the blogosphere they are out there). My family is all within normal weight range, yet we consume a *lot* of butter, cream, eggs, olive oil, raw milk aged cheese, raw whole milk and other full fat unsweetened cultured dairy foods, and meat & poultry with the fat still on it (some is direct from a farm, though, not a grocery store). My husband and I both found it much easier to maintain our weight when we stopped avoiding fat and avoided processed foods instead.
Comment by Anna — February 14, 2008 @ 2:53 am
wat is obesity about?
Comment by Aimee orwell — February 20, 2008 @ 7:14 am
The other thing to consider is that the environment part of this equation is far more than simply what one eats. It includes the culture (for the most part, America hasn’t had a very good food culture for a very long time, especially as immigrant groups assimilated into the larger social network). Lifestyle an environment aspect, too, with longer days and shorter nights due to artificial lighting and disruption of circadian rhythms.
The environment also includes the exposure to the endocrine-disrupting chemical soup that the entire world now lives in - leaching plastic compounds, PCBs, chemical waste, manufacturing by-products from non-stick pans and waterproofing chemicals, fire retardents, pesticides, herbicides, and other farm chemicals, etc. into the water, soil, air, and foods/beverages. Those are things inexcapable no matter how good the diet or even how pristine the local area seems. Because of the time lag, the limited and intentionally minimal testing, and the purvasiveness of many if not most of these toxic and persistent chemical, they are deposited in the bodies of nearly all human beings, showing up in umbilical cords, breast tissue, and newborn babies. Obesity, diabetes, thyroid disease and other endocrine issues are very possibly increasing as much because of the chemical environment as because of poor dietary choices, perhaps even more.
Comment by Anna — February 20, 2008 @ 2:41 pm
Where there is no food there are no fat people.
Comment by John Steed — March 6, 2008 @ 1:42 pm
While i do believe that genetics is a huge factor in the explanation of obesity, its pretty obvious that the decisions we make in the foods that we consume and the amount of exercise we choose to participate in may be an even larger factor. If the study is true then 77% of people have the potential to be obese since their genetics deem them to be. But why aren’t they? It all has to do with choice, one chooses to eat a salad over a Big Mac, or a bottle of water to a 32oz coke. It may be true that your genes make you more susceptible to becoming obese but for the most part you choose that life style. Very rarely would you find someone who was forced to only eat McDonalds because thats the only thing they could afford and that’s why they’re obese, so no one forces you to eat unhealthy foods and in that respect genetics doesn’t force you to be fat.
I strongly believe that its the choices that are made and the environment that a person is in that determines whether or not they will become obese.
In response to those who blame obesity on the lack of healthy and affordable alternatives, think about it like this, you could either spend $5 more on healthy food from the grocery or you can pay huge amounts of money to maintain your health in the future. The way i see it spend more now save much more later
Comment by Jon — April 16, 2008 @ 7:02 pm
“genetics explains an astounding 77% of the difference in obesity”
What does this even mean?
I have no problem with dumbing down science for the media to make it more palatable to the layman, but this claim is completely unintelligible.
Marion, care to take a crack at reading the study and trying to make any sense of this, and explaining it to us? Isn’t this your bailiwick?
Comment by Mark — April 16, 2008 @ 8:05 pm
77% refers to the correlation of obesity in twins which supports the biological/physiological/nature side of the arguement that gentics play a large role.
Comment by megan — September 9, 2008 @ 7:59 pm