Man boobs is a term to describe the medical condition of gynecomastia. Gynecomastia is the condition where a man’s breast tissue becomes enlarged causing him to have man boobs, “gyno” or “moobs”.

Gynecomastia is a lot more common than many people think and is especially common at certain times in life such as during puberty or in older age.

In most cases a man’s breast tissue grows because the levels of the ‘male’ hormone testosterone and the ‘female’ hormone estrogen change slightly.

When the level of estrogen is relatively higher than testosterone, this sends a message to the man’s breast tissue telling it to grow. Although this can be embarrassing or distressing, for most men (especially teenagers going through puberty) enlarged breasts don’t mean anything and will eventually go away on their own.

However, there are occasionally serious reasons why male breast tissue enlarges, so it is important to get the condition checked out by a doctor.

normal breast and gynecomastia

Causes of man breasts

The underlying cause of man breasts is often a change in hormone levels which tells the breast tissue to enlarge. Many things can cause this hormonal change, and some of them are quite easy to fix.

The most common time for man breasts to develop is during puberty because there is a huge surge in hormone levels, which can mean that the relative amounts of estrogen and testosterone are out of balance. This causes gynecomastia in up to 70% of teenagers, and it will usually get better on its own as the hormone levels settle down.

This can take around two years, but the usual advice is simply to wait. Older men can also develop enlarged man breasts as their testosterone levels naturally fall. This is usually nothing to worry about, and with reassurance many men learn to live with their condition.

Other common causes of gynecomastia include:

  • Some prescribed medications
  • Recreational drug use (including smoking marijuana or weed)
  • Occasionally an excess of some foods (most commonly soy)
  • Disease of the liver or kidneys
  • Rare genetic disorders
  • Hormone secreting tumours

As well as true gynecomastia in men, other things can cause the appearance of man boobs. The most common of these is a build-up of fat on the chest wall.

This is most often seen in overweight or obese men and can look very similar to gynecomastia. In fact, many men have a combination of fatty tissue and enlarged breast tissue causing their man boobs.

This is because fat encourages the body to produce estrogen, so a man who is obese will both lay down fat and grow breast tissue in response to the rise in estrogen.

Enlarged breasts can also sometimes be caused by an infection or cancer. Both of these commonly occur on one side only (rather than gynecomastia which is commonly on both sides) and may have other symptoms associated with them.

Man boobs are commonly a side-effect of some prescribed medications. If a man thinks this may be the cause of his breast swelling, he should discuss it with his doctor. In many cases, a change in medication may be possible to make sure he continues to get treated but eliminate the boobs. Some of the drugs which can cause gynecomastia are treatments for:

  • Stomach ulcer – such as cimetidine
  • Some heart problems – including digoxin
  • Depression including tricyclic antidepressants
  • Anxiety – such as Valium
  • Hormonal conditions including prostate cancer
  • Cancer – some chemotherapy drugs
  • HIV – HAART medication

Foods that cause man breasts

There are two main ways in which food can lead to man breasts. This first is simply eating too much fatty or high calorie food, causing weight gain. Being overweight can then result in pseudogynecomastia – the medical term for fat build-up on the chest wall.

Fat also encourages estrogen-like hormones to be produced, and this can cause the man’s breast tissue to grow.

The best way to get rid of these man breasts is through diet and exercise. Reducing calorie intake and cutting down on fatty foods and doing exercises to target the chest area are usually all that is needed to make the breasts go away.

Does soy cause man boobs?

Rarely, a large intake of some specific foods can result in man breasts. This is because the foods contain high levels of chemicals called phytoestrogens. These chemicals have a very similar structure to natural estrogens, which means the breast tissue responds just as it would to estrogen – and grows.

Phytoestrogens are found in high levels in soy protein. Foods that cause man boobs are those which have large amounts of soy protein such as soy milk, tofu and many vegetarian meat alternatives.

Although it is quite rare, men who are following a vegan diet, or simply avoiding dairy, may be at greater risk of man boobs. If a man thinks this might be the case, it’s worth figuring out his soy consumption and perhaps checking the labels of foods being eaten regularly to check the amount of soy they contain, as soy can often be used as a ‘filler’ in pre-made foods.

Other foods that cause man boobs

As well as soy, some people suggest that there may be other foods that cause man boobs. There isn’t a huge amount of evidence to support this, but some suggest that eating too much ‘acidic’ food might contribute to the problem. They therefore suggest eating less of a long list of acidic foods (including apples, peppers legumes and rhubarb) while increasing the intake of alkaline foods (including beets, lentils and spinach).

Does smoking weed cause man breasts?

Several recreational drugs have been linked to the development of gynecomastia. Some of these include:

  • Alcohol
  • Marijuana
  • Anabolic or “bodybuilding” steroids
  • Amphetamines
  • Heroin
  • Methadone

The most common of these is probably smoking marijuana. Although smoking weed is commonly stated as a cause of gynecomastia, there is still some doubt whether this is really true. The idea was first put forward in the 1970s, but very few studies have been done since.

We do know that when animals are given the active ingredient in marijuana, testosterone levels fall and testicles shrink. If these changes happen in people when they smoke weed then we would expect man boobs to grow.

However, we’re not sure whether smoking weed really does cause these changes in men or if it causes enough of the active ingredient to enter the system to have these effects. It is clear that if a man develops breasts and he regularly smokes marijuana, then the obvious advice is simply to stop.

If his boobs reduce in size or disappear then it’s clear that what was causing the problem was the weed, and this is a very easy solution. If the enlarged breasts stay even after he has stopped smoking weed for some time, then he should visit a doctor to discuss the problem.

This advice should also be applied to all other recreational drugs and man boobs: try stopping the drug use and see if the problem goes away. We know that steroids used in bodybuilding or to aid training are a common cause of gynecomastia.

Most men will develop boobs at some point if they continue to use anabolic steroids. Getting rid of the breasts may be a simple as stopping the steroids. However, this should be done quickly because if the gynecomastia has been there for some time then it can remain even after the steroids are stopped.

Other rare causes of gynecomastia

Other medical causes such as serious diseases of the liver or kidneys can also cause gynecomastia as they affect how the body deals with hormones.

Rare genetic disorders (such as Kleinfelter’s syndrome) and hormone secreting tumours can also be responsible. All of these will be checked out by a doctor, who will take a full medical history and perform a physical exam to try and work out what is causing the breast enlargement.


Breast tissue in men will respond to changes in hormone levels in the same way as in women. So, if the estrogen level rises or the testosterone level falls, then a man’s breasts will enlarge and cause gynecomastia or moobs.

The change in hormones can be caused by many different things, including puberty, old age, prescribed medication, recreational drugs and even some foods. For most men the problem is relatively easy to fix.

Weight loss (where needed) will help reverse the breast enlargement, as will exercise and stopping any recreational drugs. Smoking weed is the most common recreational drug thought to result in gynecomastia, and the simple advice to men who think they are affected is to stop smoking.

When prescribed medication is the cause, it is always a good idea to talk to a doctor, as there is often a different drug which can be used to make sure the condition continues to be treated while the gynecomastia goes away. For some, the problem is so severe or embarrassing that they seek treatment.

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