A healthy diet coupled with sufficient sleep and exercise leads to a longer life, right? Scientists are now learning that the right diet for one organism may not suit another and determining the best fit could be in our genes.

Researchers at the University of Southern California located a collection of genes that affect how a person responds to different diets. New findings from their study suggest a mutation in even one of these genes can have far-reaching impacts on how long we live.

"In humans, small differences in a person's genetic makeup that change how well these genes function, could explain why certain diets work for some but not others," said Sean Curran, an assistant professor at the USC Davis School of Gerontology and co-author of the study, in a release.

Researchers at USC observed the impact of two different bacterial diets on tiny worms (called C. Elegans) that have long been used to study aging due to their short lifespan.

In one group of worms the researchers inactivated a gene that effectively shut off a pathway involved in energy production. These mutant worms were then fed one of two types of bacterial diets. On one diet the mutant worms continued to metabolize food as they should and lived until they were three to four weeks old. On the second diet, the mutant worms lived roughly two weeks. Diet had no impact on the non-mutant worms.

The researchers believe that the metabolic problems in the worms with the gene mutation were caused by an energy producing pathway being shut off which led to their early demise. But researchers believe a compensatory system in the non-mutant worms allows them to process all different types of food.

"I think what's neat about this is that it's diet dependent. If you give [the mutant worms] this other diet it's as if you can't tell that they have any mutations whatsoever," says Curran in an interview.

Scientists don't yet know the specific differences between the two diets that caused one group of mutant worms to die young--they can only guess that the less ideal diet is missing some essential nutrient--but the fact that there was a clear difference suggests that the interaction between genes and diet is significant.

While it may seem a far reach to relate a study of worms to humans, the exact same gene and the exact same pathway exists in humans. Of course there is more research to be done including further tests in vertebrates -- possibly mice -- and a closer look at studies on centenarians. By sequencing the genome of the longest living adults and interviewing them to find out what diets worked for them, Curran says researchers can better understand these gene-diet pairings. For Curran, it's an exciting possibility.

"If you can imagine, at birth you could have your genome sequenced and you would know from the day that you were born what type of food would work best for you and your physiology," he says.

Before this day comes, researchers will of course need to determine all the significant genes, he and his colleagues have found just one of them.

The study was published in "Cell Metabolism" earlier this month. Shanshan Pang, a USC postdoctoral fellow also co-authored the study.