With recent stories in the news, dieters are wondering, "Can a DNA test for best diet work for me?" Here's a look at the science and the hype behind the idea.
Diet Plan Research
In March 2010, the results of a Stanford University study were presented at the American Heart Association's Physical Activity and Metabolism Conference. The 2007 study looked at 138 overweight women that spent a year assigned to one of four common diets - the low carbohydrate Zone diet, the very low carbohydrate Atkins diet, a very low fat Ornish diet, or what was termed a health professional's diet, which is a low fat diet following the U.S. Department of Agriculture's food pyramid.
The diets were not the unique part of the study. Researchers collected a DNA swab from the cheek and used the results to divide the woman by three broad subtypes: low carbohydrate diet responsive, low fat diet responsive, and balanced diet responsive. The women were then each assigned one of the four diets, but only some were assigned the appropriate diet as determined by the test. Some were also assigned what DNA testing had designated as an inappropriate diet.
A year later, researchers compared results. Not surprisingly, there were few differences between the different types of diet. Some participants lost weight, some didn't, some even gained weight. The biggest differences were seen among the participants in each individual diet. Regardless of low fat, low carb, or a balanced low calorie diet, the results were the same - participants on the plan that the DNA test for best diet had predicted as appropriate lost at least twice as much as participants on an inappropriate diet.
Science of the DNA Test for Best Diet
The DNA test used was developed by Interleukin Genetics. Body mass and obesity are affected by hundreds of genes, but researchers developing the test focused on just three that have been identified in clinical studies. In these genes, a variation on a small fragment of DNA, called a single nucleotide polymorphism, triggers the gene to change the way it functions. Essentially, this change in function combines with other genetic factors to cause the body to use some foods less efficiently, leading to weight gain.
Mindy Dopler Nelson, Ph.D., a nutritional scientist at Stanford University, spoke to HealthDay News about the study, pointing out that she often sees widely varying weight loss success from people following the same diet. She believes that how well the patient sticks to their diet explains some, but not all, of the variation.
"You do need to be on a reduced-calorie diet. You still need to eat healthy. But there is a difference in how people process calories. Knowing your genotype is just one more tool to help the weight-loss process," she says.
Avoid Getting Scammed
Researchers stress that dieters anxious to try the DNA test for best diet can be optimistic, but the study involved a very small group of patients. Dr. Robert Eckel of the University of Colorado School of Medicine told HealthDay that he wouldn't recommend the diet testing until the results were confirmed by larger studies. "This could explain small differences in the way people respond to diet. But right now the most important predictor of successful dieting is compliance."
These cautions have not stopped companies from offering kits that promise to give customized diet advice based on DNA, a practice that began before the study was even done. As early as 2006, investigators from the Government Accounting Office (GAO) bought kits from four websites, and created 14 fictional customers using DNA samples from just two people. In return, they received such generic health advice as warnings to stop smoking and that a poor diet can lead to heart disease. Some companies attempted to mislead these 'customers' into making additional expensive purchases, such as dietary supplements and vitamins costing hundreds of dollars.
Before buying any DNA based diet, be sure what you're getting. The test used in the study is available from Interleukin Genetics for $149.00. This includes the test, personalized diet and exercise recommendations, a one-on-one phone consultation with a genetic expert, and access to their online weight loss tools.