The strategy is structured around a whole-food, plant-based diet, moderate daily exercise, yoga-based relaxation and stress management, they said.
Researchers recruited 35 men, 10 of whom were asked to follow this lifestyle, while the other 25 were not asked to make any lifestyle changes at all.
In addition to the diet and daily physical and mental routines, the 10 also attended weekly sessions for three months where their new skills were reinforced by specialists, including a one-hour weekly "support" session.
After five years, the scientists assessed the participants for a hallmark of biological ageing called telomeres.
Telomeres are nubby pieces of protein that are attached to the end of chromosomes. They help to protect the precious strings of DNA code when a cell replicates.
They are often likened to the tips of shoelaces. As the telomere wears down, its protection erodes too, and so does the risk that the DNA is not faithfully replicated in the daughter cell, which boosts the risk of cellular malfunction and then disease, including cancer.
Looking at the length of telomeres thus gives a telltale of cellular lifespan.
Among the 10-man group, telomere length increased significantly by an average of 10 percent over the five years -- and it was higher among those who had adhered most faithfully to the new lifestyle.
Among the "control" group, though, telomeres had shrunk by three percent on average.
The study has limitations as the number of recruits was small, and it was conducted as part of an investigation into prostate cancer.
In addition, the research was not empowered to test whether lifestyle changes affected the risk of cancer.
But, say its authors, its focus on the vital telomeres was carried out scientifically and over the long term.
This is what makes it new compared with evidence that is anecdotal or only short-term.
"The implications of this relatively small pilot study may go beyond men with prostate cancer," said Dean Ornish, a professor at the University of California in San Francisco, who led the study.
"If validated by large-scale randomised controlled trials, these comprehensive lifestyle changes may significantly reduce the risk of a wide variety of diseases and premature mortality.
"Our genes, and our telomeres, are a predisposition, but they are not necessarily our fate."
Ornish is the founder of the not-for-profit Preventive Medicine Research Institute at the university. He has vigorously promoted in medical presentations and books the argument that lifestyle changes, especially a shift in diet, can protect against disease.
The study appears in the journal The Lancet Oncology.
