In a new study, scientists have discovered that the secret to weight loss and metabolism lies beyond our plates. Researchers at the University of Virginia, including Dr Susanna Keller and dietitian Sibylle Kranz, embarked on a five-year journey with mice to unravel the mystery of dieting efficacy.

The rodents were fed diets mimicking vegan, vegetarian, Mediterranean, and typical American eating habits, all calibrated for equal calories, carbs, proteins, and fats. Prof Kranz told WVTF: "We set certain standards for nutrients that we wanted to achieve. No matter what the diet was. It all had to have the same amount of calories, the same amount of carbohydrates, proteins and fats."

Despite the controlled conditions, the results varied wildly among the different mouse strains. Prof Kranz observed: "We had one strain that gained the most weight on all the diets, and then we had this other strain that just didn't gain weight on any of the diets. The American diet was the one that caused the most weight gain in that particular strain."

The investigation also delved into how these diets impacted blood sugars and fats, leading to surprising findings. Prof Kranz remarked: "We always assumed that diet will affect everybody in the same way, or at least somewhat in the same way, and we now have measurable outcomes that demonstrated that is just not happening."

Dr Keller pointed out that genetics play a pivotal role in these differences: "The genetic background has a much more prominent impact than diet on body weight gain, blood sugars and fats as well as gene activity."

According to Prof Kranz, diets should be tailored to an individual's genetic makeup in order to be more effective. She said: "We're just really scratching the surface of something that has not been looked into before. Should you really tell everybody to eat a certain way because it's healthier? Probably not, because for different individuals, different things might be healthier.

"Ideally we'd have something where you can come in and maybe you spit in a cup, and right there we can analyse your whole genome, and then we can tell you what are higher risk factors for you, and what kind of diet you can use to have the best beneficial outcomes."

Prof Kranz and Dr Keller cautioned against relying solely on weight as a measure of health, pointing out that some individuals classified as overweight may be metabolically healthy.