You probably have that one friend who raves about the latest diet and ends up convincing you to slim down together by burning fat, and eating healthy. Despite following the same exercise regimen and diet plan, the weekly weigh-ins look more favorable for your friend, while you actually gain more weight. Now, a study to be presented at the Allied Genetics Conference on July 15 in Orlando, Fla., a meeting hosted by the Genetics Society of America, suggests that the best diet for you may be linked to your genetics.

"Our study showed that the impact of the diet is likely dependent on the genetic composition of the individual eating the diet, meaning that different individuals have different optimal diets" said William Barrington, study author from North Carolina State University, who conducted this study in a lab at Texas A&M University, in a statement.

Barrington and his colleagues sought to discover the best diet for humans by studying mice. These rodents have similar susceptibilities to obesity and metabolic syndrome — a group of conditions that increase the risk of heart disease, stroke, and diabetes — that can help model the genetic diversity seen in humans. The researchers used four different genetic strains to observe the effects of different diets on groups of mice that had the same gene makeup, representing the genes of one person. Genetic differences between any two strains were similar to that of two unrelated people.

Over a six-month period, different mice in each group were fed one of the five diets, including the modern Western diet, higher in fat and refined carbs; a traditional Japanese diet, with rice and green tea; a traditional Mediterranean diet, with wheat as the main source of carbs and red wine; or a high fat low carb Atkin's-like diet also known as a ketogenic diet. The final group of mice, the control, received standard mouse chow.

The mice could eat as much food as they wanted, but the researchers observed how much of it was consumed. And the findings revealed the effects of each diet were strongly contingent on the genetics of the mice.

Overall, the Western diet had negative effects for all of the mice, including increased obesity, fatty liver disease, and detrimental effects on cholesterol. The severity of these conditions depended on the genetics of the mice; however, one group of mice were largely resistant to any negative health effects from the Western diet.

Interestingly, the ketogenic diet, which is also high in fat, showed varying effects for several groups. Two of the mice groups saw no negative health effects while on the low-carb diet, while two other groups had increased obesity and signs of metabolic syndrome. The latter was much healthier on the Western diet.

The researchers also found the causes for obesity were different.

"Some mice on specific diets simply ate more calories, and this caused them to become obese. However, mice on other diets ate less but still became obese” said Barrington.

In addition, the ketogenic diet increased calorie burn without an increase in physical activity. Some groups of mice ate so much on this diet that they still became obese and experienced negative health effects. Meanwhile, the Mediterranean and Japanese diets did well for most mice, although some still had weight gain or liver problems.

So, the best diet for you solely depends on who you are — your DNA.

Although these results cannot be applied to humans yet, researchers believe further studies that support these findings could potentially lead to a more personalized approach to dieting.

Currently, the FDA has nutritional guidelines for all individuals, but just like clothes, a "one-size-fits-all" approach is not applicable. These recommendations are based on average responses of people, which could be irrelevant to others.

Barrington notes for the last 100 years, doctors have viewed diet the same way, assuming there is only one optimal diet for all.

"Now that we've identified that this is likely not the case, I think that in the future we will be able to identify the genetic factors involved in the varying responses to diet and use those to predict diet response in humans,” he said.

Similarly, previous research has found it’s harder for some people to lose weight than others because of their genes. However, these genes are only a small part of how human metabolism works. Environmental factors can also influence dietary intake and how effectively you’re able to metabolize food. For example, some people will consider nutrition to be more important in their lives, while others will say physical activity.

So, when you and your friend go on a diet, and it works for one person, place the blame on genetics, and not the pizza you had after your workout.

Source: Barrington W et al. Pathophysiological Responses to Dietary Patterns Differ With Genetic Backgrounds. The Allied Genetics Conference. 2016.