UVA doctor Susanna Keller, dietician Sibylle Kranz and their colleagues studied four different strains of mice that were given a vegan, vegetarian, Mediterranean or typical American diet. Kranz says it was a challenge creating each kind of mouse chow given their goals.
“We set certain standards for nutrients that we wanted to achieve. No matter what the diet was. It all had to have the same amount of calories, the same amount of carbohydrates, proteins and fats,” Kranz explains.
With funding from the university, Keller says, they spent five years documenting what happened to each genetically different group of mice when eating the different diets.
“We had one strain that gained the most weight on all the diets, and then we had this other strain that just didn’t gain weight on any of the diets.”
Although, Keller adds, for mice that gained weight, one diet really packed on the pounds or ounces.
“The American diet was the one that caused the most weight gain in that particular strain.”
They also studied blood sugars and fats, finding there too that different diets did not produce predictable results. Again, Professor Kranz.
“We always assumed that diet will affect everybody in the same way, or at least somewhat in the same way, and we now have measurable outcomes that demonstrated that is just not happening.”
The reason, Keller concludes, is the fundamental role played by genetics.
“The genetic background has a much more prominent impact than diet on body weight gain, blood sugars and fats as well as gene activity.”
In other words, the way we metabolize foods probably depends to a large extent on our unique DNA. Kranz says it’s time to stop telling everyone to eat a certain way, and we need more research – in animals and humans -- to create custom diets based on genetics.
“We’re just really scratching the surface of something that has not been looked into before. Should you really tell everybody to eat a certain way because it’s healthier? Probably not, because for different individuals, different things might be healthier.”
Someday, she and Keller hope humans can design their diets based on genetics.
“Ideally we’d have something where you can come in and maybe you spit in a cup, and right there we can analyze your whole genome, and then we can tell you what are higher risk factors for you, and what kind of diet you can use to have the best beneficial outcomes.”
But she cautions that today’s commercial genetic tests based on saliva or hair samples should not be used to help consumers eat for good health.
“For weight loss, for muscle-building, for diabetes prevention or diabetes treatment, there are companies out there that charge decent amounts of money to then tell people what they should be eating, based on whatever samples they sent in, and what we see is that a lot of this not scientifically supported.”
And both Keller and Kranz advise the public not to consider weight as the sole indicator of health. Some people who are branded overweight are actually quite healthy based on other measures of metabolism.
