Plentiful skin moles may keep you younger on the inside, say scientists.
Researchers at Kings College London found that they not only could mean younger skin, but better bone density as well.
They said that the cells of people with many moles had properties which allowed them to renew themselves more often.
However, there may be a price to pay - more moles have been linked to a higher rate of cancer, both skin and other types.
Most people have between 30 and 40 moles, but some have as many as 600.
A series of studies carried out by the King's College team, and Dr Veronique Bataille, a dermatologist based at Hemel Hempstead General Hospital, looked at the relationship between mole numbers and other physical characteristics.
First Dr Bataille noted that people with large numbers of moles appeared less vulnerable to some of the effects of skin ageing, such as wrinkles and blemishes.
The latest study in 1,200 twins suggested that high mole numbers also meant that people were less affected by age-related reductions in bone density, which could mean a lower risk of brittle bone disease and bone fractures later in life.
Those with more than 100 moles were half as likely to develop osteoporosis compared with those with 25 moles or fewer.
The reason for these links are unclear, but researchers have noticed that people with large numbers of moles have differences in the strands of DNA in each cell which carry their genetic code.
Sections on the end of these strands are called telomeres, and are effectively a countdown timer governing the number of times a cell can divide to produce new cells.
The longer the telomere, the more cell divisions can take place over a lifetime - and more moles were linked to longer telomeres.
Dr Bataille, who presented her findings at a Royal Society of Medicine conference, suggested that moles were a visible product of the underlying system which controls body ageing.
She said: "Some people will have two moles, some people will have 600, but when you have a patient with lots of moles, we noticed they tended to age better."
But she said that tinkering with this system to produce an "elixir of youth" was bound to prove tricky.
"We have a DNA system produced over millions of years of evolution - I don't think it will be easy to produce a cream that can alter that."
The underlying ageing mechanism could be a trade-off which allowed longevity without unduly raising the risk of cancer, she said.
Those with more cell divisions, and more youthful looks, might be increasing their cancer risk.
"As a clinician, when I get a patient with lots of moles, I automatically want to know about their family history of cancer, so I can think about prevention.
"This is not just melanoma, but also more common cancers such as breast and colon cancer."