More and more men are seeking surgery to reduce the size of their breasts, say UK surgeons.
With gynaecomastia the breast takes on a womanly shape
Professor Kefah Mokbel at London's St George's and Princess Grace hospitals has seen a doubling in requests and is now treating 150 men a year.
Gynaecomastia is not a new phenomenon, but it would appear anecdotally that the rates are rising.
It is different from the flabby breast tissue that goes hand in hand with obesity in men.
In gynaecomastia there is glandular breast tissue as well as fatty tissue.
Some experts believe it may be down to female hormones leaking into the environment.
Dr Alan Kingdon of The Cosmetic Surgery Clinic in Harley Street has studied the material removed from men's breasts and has found that often the tissue is identical to that normally found only in women.
"The breast does take on an appearance very much like a female breast and it is a source of great embarrassment to patients.
"We do seem to be seeing more and more of it. There is even a slang term for it - man boobs."
Dr Kingdon said: "Whilst there are no proven causes for this increase in breast formation in the male, I feel that the use of oestragens in the meat industry is a factor."
These steroid hormones are used to make livestock grow big, ready for slaughter.
Experts are also concerned that men are inadvertently exposed to oestrogen via water supplies.
How the breast looks before (left) and after (right) surgery
Women taking oral contraceptive pills are blamed for this contamination. Small quantities of oestrogens are excreted from the body and enter the sewage system.
The UK Environment Agency scientists have already reported that fish are developing female characteristics, including reproductive organs, because of such exposure.
There are other recognised causes of gynaecomastia. Many boys going through puberty will develop a degree of breast growth, but this usually resolves itself.
Certain drugs can trigger glandular breast growth in men, as can some rare genetic and hormonal diseases, as well as excessive alcohol consumption.
Although gynaecomastia is not medically threatening, it can be very distressing.
Men may feel intense embarrassment and that their sexuality and virility is in question on the beach, in the changing rooms and in the bedroom.
Dr Kingdon said: "Some men will not want to undress in front of their partner or would never take their shirt off on the beach. The patients we see can suffer for quite a long time before they come along."
It can be corrected with surgery that can be done as a day case, under local anaesthetic and sedation.
Any excess fat is sucked out with liposuction, but the excess glandular tissue has to be removed through a u-shaped incision around the nipple.
Dr Kingdon said: "The scars heal to be pretty well invisible.
"We normally advise patients to take two or three days off work and that they can return to full physical activity, including gym work, after 10 days."
Once the tissue has been removed it should not return. However, if the tissue is mostly fat in an obese patient, he will have to pay attention to diet and exercise to maintain the result, he said.