Some whose genetic markers indicated a low-carb diet would work better for them did not lose significantly more or less weight on either kind of diet, and the same was true for low-fat dieters.
The researchers found no evidence that some people are genetically adapted to respond better to one type of diet than another.
Researchers set out to determine whether your DNA-specific genes and insulin levels-could complement different diets and spur greater weight loss.
A team from Stanford University School of Medicine rounded up 600 adults who were overweight or obese (as determined by their body mass index) but otherwise healthy, and put them on either a low-fat or low-carbohydrate diet for 12 months.
"Unfortunately, it still remains unclear which diet is the best for weight loss, and who the true demons really are ... carbs or fat", she says. Those on the low-fat diet improved their "bad" LDL cholesterol more, while the low-carb group improved their "good" HDL cholesterol and reduced their triglyceride levels more. At the end, both groups had lost about the same amount of weight, on average.
You're determined to lose weight this time and find yourself debating whether to go low-fat or low-carb? Both groups were instructed to eat lots of vegetables and very few foods with added sugars, trans fats, or refined flour.
Participants who lost the most weight reported that this approach reshaped their relationship with food and made them more thoughtful about how they ate, he added.
The low-fat group was initially encouraged to cut down to 20g a day of fat, and the low-carb group to 20g a day of carbohydrates. They were split into one of two dietary groups: low-carbohydrate or low-fat.
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The strategy worked for people whether they followed diets that were mostly low in fat or mostly low in carbohydrates. The Centers for Disease Control and Prevention, for example, tells people who are trying to lose weight to "write down the foods you eat and the beverages you drink, plus the calories they have, each day", while making an effort to restrict the amount of calories they eat and increasing the amount of calories they burn through physical activity. The weight loss average was 13 pounds among those studied, but some lost as much as 50-60 pounds. They simply stopped eating in front of the TV or in their cars.
What's key, Gardner said, was emphasizing that these were healthy low-fat and low-carb diets: A soda might be low-fat, but it's certainly not healthy.
Gene activity is undoubtedly involved in the process of gaining and losing weight, this study simply shows that these particular predisposing variants (many others have also been identified) are now unable to lead us toward personalized, magic wand diet plans.
"A couple weeks into the study people were asking when we were going to tell them how many calories to cut back on", he said.
They say the differences from previous study findings may be because this study stressed the importance of eating healthy whole foods, rather than eating any food so long as it was either low-fat or low-carb.
'This study closes the door on some questions - but it opens the door to others.
There is an opportunity to discover some personalisation to it now we just need to work on tying the pieces together.' Tam Fry, of the National Obesity Forum, said: It is refreshing to see Dr Gardner's honesty.
I'm hoping that we can come up with signatures of sorts.