Dieting is ubiquitous in America. Most people have either been on a diet, know people who are on a diet now, or know someone who's whining that they need to start watching what they eat. We'll bet that a large majority of Americans have tried a plethora of different diets, and that many of those diets have inevitably failed.
In the study, researchers grouped mice into four different groups. Each group was genetically similar, but slightly different—roughly analogous to humans who aren't related. The researchers then gave the mice five different diets for six months: American (high in fat and refined carbs), Mediterranean-style (wheat and red wine extract), Japanese (rice and green tea extract), ketogenic (high fat and protein with low carbs), and a control diet (regular animal feed).
After six months, the researchers realized that no matter the diet, some mice suffered from bad reactions (weight gain, fatty liver, and high cholesterol) while others remained healthy and lean with no problems. The only exception to that rule was the American-style diet: none of the mice fared well.
"My goal going into this study was to find the optimal diet," said William Barrington, Ph.D., lead author on the study. "But really what we're finding is that it depends very much on the genetics of the individual, and there isn't one diet that is best for everyone.
"One day, we'd love to develop a genetic test that could tell each person the best diet for their own genetic makeup. There might be a geographical difference based on what your ancestors ate, but we just don't know enough to say for sure yet."
So if you're feeling frustrated with your current diet plan despite lots of fastidious effort, it might be a sign that you should switch things up. Talk to your doctor or a nutritionist, and check out our guide to creating a healthy diet plan.