by Marion Nestle
Jan 8 2010

Genetic causes of obesity: 1%?

Recent news reports encouraged me to take a quick look at the January 2010 American Journal of Clinical Nutrition where investigators have attempted to identify the proportion of human obesity accounted for by genetic variation.  Their conclusion: probably no more than 1% (we used to think it was 5%).  I don’t know why anyone would be surprised.  Obesity rates rose sharply in the early 1980s, with no possibility for so rapid a change in the genetic composition of the population.

I don’t think we need complicated genetic explanations for obesity.  We have so much evidence that people started consuming more calories at about that time and are continuing to do so.  Why more calories?  Portion sizes got bigger, and – hard as it may be to believe – larger portions have more calories!

In a commentary on the study, Claude Bouchard puts it this way:

The obesity epidemic we are facing today unfolded over the past few decades and can clearly not be explained by changes in the frequency of risk alleles. It is more likely due to a changing social and physical environment that encourages consumption and discourages expenditure of energy, behaviors that are poorly compatible with the genome that we have inherited.

Hence: eat less, move more!  And have an active weekend!

Comments

  • LindsayB
  • January 14, 2010
  • 7:08 am

in-utero exposure to some endocrine disruptors in mice has been shown to increase the weight of the pups by 30-40% with the same calorific intake as their non-obese cousins. It is simplistic to say that over consumption and lack of exercise are the only factors at play here.
Similarly, just because no genetic mutations have been observed to cause obesity does not mean that genes in the obese are behaving in the same way as they are in the non-obese. Environmental factors are known to change gene expression, and this change can be heritable.
Obesity is a complex problem, so let’s not close our minds to the possibility that environmental polutants and changes to the food supply over the past decades may play some role here, in addition to chronic lack of activity and ready availability of poor quality food.

  • Cathy Richards
  • January 14, 2010
  • 8:16 pm

A few posters have taken one sentence from Marion’s blog — out of context — and generalized it to her entire belief system. It would be fairer to look at things in the context she presents them in and become knowledgeable with many of her postings/writings and work area before drawing any conclusions.

[...] Genetic causes of obesity: 1%? <<To me it always feels silly to talk about the genetic causes of obesity, since obviously the problem is relatively new and started around the time we embraced the low fat (high sugar) lifestyle. But it is always good to examine the data supporting any hypothesis. (Food Politics) [...]

  • Marcia
  • January 15, 2010
  • 9:36 am

Back to the subject of how your lifestyle can change your body without your DNA…I will fess up to watching The Biggest Loser. And I’ve noticed that the younger folks who have NEVER been fit have a much harder time that older folks who were fit when they were younger.

Which could be partially mental. But when you are a child through teen years, that’s when your body makes most of it’s body fat. If you are fat when you are younger, your number of fat cells will be greater…hence, tougher weight loss.

Katelyn, it’s not carbs, it’s calories. Sure, there are more carbs these days…which have calories. I’m a near-vegetarian that eats a large percentage of carbs…but I don’t overeat calories.

  • Hugo X
  • January 15, 2010
  • 11:52 am

Who ever said that Americans have low-fat diets today? When I open my eyes and look around I see high-sugar, high-calories, more protein than is needed and very high (saturated) fat intake. In the context of obesity however – the calories count.

[...] Food Politics: Genetic Causes of Obesity – 1% The American Journal of Clinical Nutrition just found that only 1% of us can blame obesity on [...]

[...] Food Politics: Genetic Causes of Obesity – 1% The American Journal of Clinical Nutrition just found that only 1% of us can blame obesity on [...]

Larger portion sizes of processed foods, less active lifestyles all contribute to the obesity problem in America today.

Simply by eating more natural foods and walking, the problem would begin to slowly reverse itself.

Peter
http://www.fitnessover50.org

Reducing the amount of processed foods and increasing the amount of activity – even simple walking would go a long way to improving the obesity problem

[...] Genetic Causes of Obesity: 1%? at Food Politics “A New York City law requiring restaurants to post the calories of their menu items led [...]

[...] Food Politics: Genetic Causes of Obesity – 1% The American Journal of Clinical Nutrition just found that only 1% of us can blame obesity on [...]

[...] Food Politics: Genetic Causes of Obesity – 1% The American Journal of Clinical Nutrition just found that only 1% of us can blame obesity on [...]

[...] Food Politics: Genetic Causes of Obesity – 1% The American Journal of Clinical Nutrition just found that only 1% of us can blame obesity on [...]

[...] Food Politics: Genetic Causes of Obesity – 1% The American Journal of Clinical Nutrition just found that only 1% of us can blame obesity on [...]

[...] Food Politics: Genetic Causes of Obesity – 1% The American Journal of Clinical Nutrition just found that only 1% of us can blame obesity on [...]

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