Going on a health kick reverses ageing at the cellular level, researchers say.
The University of California team says it has found the first evidence a strict regime of exercise, diet and meditation can have such an effect.
But experts say although the study in Lancet Oncology is intriguing, it is too early to draw any firm conclusions.
The study looked at just 35 men with prostate cancer. Those who changed their lifestyle had demonstrably younger cells in genetic terms.
The researchers saw visible cellular changes in the group of 10 men who switched to a vegetarian diet and stuck to a recommended timetable of exercise and stress-busting meditation and yoga.
The changes related to protective caps at the end of our chromosomes, called telomeres.
Their role is to safeguard the end of the chromosome and to prevent the loss of genetic information during cell division.
As we age and our cells divide, our telomeres get shorter – their structural integrity weakens, which can tell cells to stop dividing and die.
Researchers have been questioning whether this process might be inevitable or something that could be halted or even reversed.
The latest work by Prof Dean Ornish and colleagues suggests telomeres can be lengthened, given the right encouragement.
They measured telomere length at the beginning of their study and again after five years.
Among the 10 men with low-risk prostate cancer who made comprehensive lifestyle changes, telomere length increased significantly by an average of 10%.
In comparison, telomere length decreased by an average of 3% in the remaining 25 men who were not asked to make any lifestyle changes.