One diet does not suit everybody
Dietary advice, whether it comes from the United States government or some other organisation, tends to be based on the theory that there is going to be one diet that will help everyone,” says David Threadgill, with the Texas A&M College of Medicine and College of Veterinary Medicine & Biomedical Sciences and senior author of the study that appears in Genetics. “In the face of the obesity epidemic, it seems like guidelines haven’t been effective.”
For the new study, researchers used four different groups of animal models to look at how five diets affect health over a six-month period. The genetic differences within each group were almost non-existent, while the genetics between any two of the groups would translate to roughly the same as those of two unrelated people.
The researchers chose the test diets to mirror those eaten by humans-an Americanstyle diet (higher in fat and refined carbs, especially corn) and three that have gotten publicity as being “healthier,” including Mediterranean (wheat and red wine extract); Japanese (rice and green tea extract); and ketogenic, or Atkins-like (high in fat and protein with very few carbs). The fifth diet went to the control group, who ate standard commercial chow.
Although some so-called healthy diets did work well for most individuals, one of the four genetic types did very poorly when eating the Japanese-like diet, for example. “The fourth strain, which performed just fine on all of the other diets, did terrible on this diet, with increased fat in the liver and markings of liver damage,” says lead author William Barrington, a recently graduated PhD student in Threadgill lab. A similar thing happened with the Atkins-like diet: two genetic types did well, and two did very badly.
“One became very obese, with fatty livers and high cholesterol,” Barrington says. The other had a reduction in activity level and more body fat, but still remained lean. “This equates to what we call “skinny-fat” in humans, in which someone looks to be a healthy weight but actually has a high percentage of body fat. “In humans, you see such a wide response to diets. We wanted to find out, in a controlled way, what was the effect of the genetics.”
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