Obesity has been blamed for the growing problem of “boy-boobs” – cases of teenage boys with breasts so well developed that surgery is needed to reduce them.

Doctors at Alder Hey Hospital in Liverpool say that they are seeing dozens of teenagers every year with gynaecomastia, the condition in which males develop breasts.

Christian Duncan, a plastic surgeon specialising in obesity-related surgery, said that in the past 12 months he had performed at least 20 breast-reduction operations on young boys who had developed the condition.

Mr Duncan is treating others who do not yet qualify for surgery by encouraging them to make changes to their lifestyle, such as starting a healthy diet or beginning an exercise programme.

He believes that the condition is becoming more common among teenage boys in Liverpool, and that it can cause “terrible damage” to their lives and their self-esteem.

While some boys are simply fat, giving the appearance that they have breasts, those who develop gynaecomastia face a greater problem: the growth of firm female breast tissue under the nipples, Mr Duncan said. This condition is caused by a hormone imbalance during adolescence and in many cases resolves itself naturally. There is some evidence that the imbalance can be triggered by obesity.

Mr Duncan said: “This is different to someone just being overweight. These are firm female breasts, something that any woman would be proud of. There isn’t one month that has passed in the past 12 months where I have not seen a new patient with this condition. It used to be much less common and I am afraid it is a sign of the growing problem of childhood obesity.

“We try to teach these boys about making lifestyle adjustments, like getting them to go to the gym, but they just won’t go. They become very self-conscious and it can start to affect their ability to socialise and concentrate at school. Often they are bullied. To rectify the problem for them we basically use liposuction to remove the glandular and breast tissue and fat from around the chest to give a flatter appearance.”

Mr Duncan said he believed that the boys’ poor diet was causing an imbalance in their hormones, resulting in their developing breasts.

He said: “Both men and women have breast tissue but there is something about obesity that triggers hormone imbalances and causes an unnatural growth in these boys.

“If nothing is done to stop the growing tide of childhood obesity in the city I expect to see more cases year-on-year.”

More than one cause

— Breast reduction operations in men have increased sharply in recent years. Whether this increase is because of a greater incidence of gynaecomastia or a greater availability of cosmetic surgery is unclear

— In men the condition can have a number of causes, including body-building drugs, recreational drugs, cancer, diseases of the liver or kidney, and obesity. It may affect one breast, or both

— Some doctors have blamed increased levels of female hormones, or chemicals that mimic their effect, that are in the environment. In boys, the condition is very common but usually resolves itself without treatment as the hormone balance in the body stabilises at the end of adolescence