Researchers from the United States who examined hundreds of participants suffering from obesity found that the amount of fat or carbohydrates in the menu is not what determines how much weight you lose.
The study also raised questions about claims that a genetic profile exists that determines which diet fits you best.
The researchers said the way to lose weight is to eat healthier, less processed food and more vegetables.
The battle between carbohydrates and fats ended in a tie.
American researchers who examined hundreds of participants found the answer to the question which diet leads to the greatest weight loss, low carbohydrate or low fat.
The results will disappoint supporters of both methods.
The findings were published in the new issue of the journal JAMA.
In the study, which lasted one year, 609 men and women aged 18 to 50 who suffered from overweight or obesity participated. They were divided into two groups.
One was asked to reduce the amount of carbohydrates in the daily menu and the other the amount of fat. The participants were instructed to enrich the menu with vegetables and reduce processed foods as much as possible.
On average the participants consumed about 600 to 500 fewer calories compared to the menu they consumed before the study began.
At the end of the year the results showed there was no significant difference in the average weight loss of the two groups.
In the low fat menu group the average weight loss was 11 pounds while in the low carbohydrate group the average weight loss was 13 pounds.
Within this, the researchers assumed that certain genetic and metabolic markers found in previous studies might predict who would succeed more and in which diet.
But the current study showed this was not the case.
About 30 percent of the participants had a genetic signature that in theory was supposed to show success in a low fat diet while 40 percent had a genetic profile that was supposed to show a low carbohydrate diet fit them more.
However the study did not find any match between the genetic profile and the chances of success in either diet. The researchers also examined insulin resistance which in the past was considered a predictor of success in different types of diets but again no connection was found between insulin resistance and success in any diet.
The lead researcher said it would be very nice to know through a simple genetic test which diet suits you more but that is not the situation.
What they found is that it is not the type of diet that leads to success but your relationship with food and your thinking about what you eat.
He also recommended eating less sugar less processed flour and as many vegetables as possible. He said to choose whole foods whether it is a salad of wheat grains or beef fed on grass.
From both study groups they heard from people who lost weight that they were helped to change the relationship they developed with food and now they eat more thoughtfully and think about what they eat.