An illustration of a strand of DNA. Does it hold the key to effective dieting? (Photo:Zephyris)

DNA diets, also known as gene-based nutrition interventions, are being touted as the latest sure-fire way to lose weight. It makes sense right, using your own DNA to tailor a diet to your body?

But the diet is based on sketchy science at best, and may be no more than another fanciful and expensive diet scam at worst.

Numerous companies have sprung up claiming to use DNA analysis to personalize a diet. But experts say, when it comes to diet advice, its misleading to say that the blueprint is our genes.

DNA is important, but it plays a pretty minor role in making personal decisions about food, says Dariush Mozaffarian, a cardiologist and dean of the Friedman School of Nutrition Science and Policy at Tufts University.

And now more scientific evidence backs that up.

Scientists released a new studythe most rigorous so far that found no difference in weight loss between overweight people on diets that matched their genotype and those on diets that didnt.

Knowing genetic risk information doesnt have a big impact, Timothy Caulfield, a University of Alberta scientist told Scientific American magazine.

Simply put, diets cant be matched to genotype, the new study shows.

For basic healthy living, its not about your genes, its about your behavior, Mozaffarian says.

The study was conducted by researchers at Stanford University Medical School. The results were published in the Journal of the American Medical Association.

It randomly assigned 609 overweight adults, aged 18 to 50, to either a healthy low-fat or healthy low-carb diet.

Dietitians guided the volunteers on healthy low-fat diets (eat less oils, fatty meats, full-fat dairy, and nuts) and low-carb diets (reduce cereals, grains, rice, starchy vegetables, and legumes).

Both groups were instructed to eat lots of vegetables and very few foods with added sugars, trans fats, or refined flour.

A year later, the two diets produced near identical results: an 11.7 pound weight loss in the low-fat group and 13.2 pound loss in the low-carb group. The difference was not statistically significant or meaningful in real life.

The researchers then analyzed weight loss among people whose DNA matched or clashed with their assigned diet.

No significant difference in weight change was detected among participants in matched and mismatched diets, the researchers found. There was also no DNA/diet interaction for waist circumference, body mass index or body fat percentage.

Diets mostly come down to factors other than your genes, Mozaffarian told CNN. Its your age, how much extra weight youre carrying, how you respond to eating starch or sugar, and potentially even your microbiome, that are much more important, he says.

He says cutting back on snack foods and junk foods that contain lots of refined starch and sugar is good advice for everyone. But, he says, there are significant differences from person to person in blood glucose responses after eating these foods.

Of course, a number of companiessuch as Habit, Profile Precise and Nutrigenomixhave sprung up pushing DNA-based diets, and a number of media outlets have blithely touted their claims.

Even specialized publications like Health.com, which should know better, have promoted the diets.

The companies provide customized meal plans, grocery lists, recipes, and even exercise routines, typically based on AncestryDNA or 23andMe DNA results.

But dieters should beware, especially if the meal plan eliminates entire food groups. If the recommendation is based on DNA, it has no basis in science.

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DNA Diet Hailed as Key to Weight Loss, But Don't Bet Your Genes On It - Celebrity Health & Fitness