Genetics Affect Weight

This New York Times article by Gina Kolata isn’t totally news to me. At least not this summary of a study published in a 1990 issue of The New England Journal of Medicine (bolding added):

The work fascinates Claude Bouchard, a genetics researcher at the Pennington Biomedical Research Center in Baton Rouge, La., because it might offer insight into an intriguing finding: there are genetic controls not just of how much people want to eat but also how much of what they eat turns into fat or is burned off and not used by the body. Although the common mantra is that a calorie is a calorie and 3,500 extra calories eaten equals a pound of fat on the body, that is not what happens in real life, he found.

For example, in one of his studies, Dr. Bouchard enlisted 12 pairs of lean identical twins to live in an enclosed area for 120 days so their food and exercise could be monitored while they ate 1,000 calories a day more than needed to maintain their weight. The twins in each pair gained about the same amount of weight, but the amount gained varied threefold among the pairs. Those who gained the most put on as much as 29 pounds while those who gained the least put on 9 ½ pounds.

“It is not a freak finding,” Dr. Bouchard said, adding that about 20 studies found the same threefold range in weight gain in response to excess calories.  

 …and, in fact, this isn’t news to anyone who’s read Health At Every Size by Linda Bacon, PhD.  What is new is more information about a particular gene that appears to be involved.

The mice were eating their usual chow and exercising normally, but they were getting fat anyway. The reason: researchers had deleted a gene that acts in the brain and controls how quickly calories are burned. Even though they were consuming exactly the same number of calories as lean mice, they were gaining weight. [...]

[This] may help explain why some people put on weight easily while others eat all they want and seem never to gain an ounce. It may also offer clues to a puzzle in the field of obesity: Why do studies find that people gain different amounts of weight while overeating by the same amount? [...]

[Reasearchers] are now trying to determine whether additional mutations in the gene they discovered — ones that hinder its function but do not completely disable it — might explain why some people gain weight.

This research may lead to a better understanding of why some people are naturally very large and others aren’t.  It may also be useful in helping to spread some pesky, little-known facts:

  • Body weight is strongly inherited.
  • Some fat people eat the same amount food, or less food, as some thin people.
  • In studies where people deliberately eat more than they do normally, different people gain weight at different rates.
  • Twins in those studies, who overeat by the same amount, have almost identical weight gains.
  • An addition or subtraction of 3500 calories does not automatically mean gaining or losing a pound.

If this is new information for you or you just want one link to reference when needed, it’s on the NY Times site.

5 thoughts on “Genetics Affect Weight

  1. I am actually wondering if I am adopted there are so many thin people in the family, I am talking bone thin-elite thin. And they don’t do anything special to be that thin, seen them eat just as much. Would one fat grandmother render one fat?

  2. All this talk of gene studies could lead down a dangerous path. Already you can choose the gender of your baby with IVF: the X chromosome sperm is larger than Y, making it easier to single out. Next they will be advertising the ability to make the perfect baby without any “bad” genes that will make them an acceptable body shape or size, or skin condition, allergies, etc.

    Eugenics anyone?

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