Testosterone injections can trigger drastic long-term weight loss in obese men, a German study has found.

Men with an average weight of 18 stone (114kg) saw their weight drop by 4st and 3lbs (27kg) over a decade while having the jabs every three months as part of a study.

Their body mass index (BMI) went from the ‘severely obese’ category, of 36.8, to ‘overweight’, at 28.8, just four points off the healthy weight range.

In comparison, men who were not given the testerone therapy saw their weight increase by almost a stone each (6kg).

They were also more than four times more likely to die during the follow-up period, particularly of heart attacks and strokes, and almost all had type 2 diabetes.

The researchers said their findings should help push testosterone injections as an alternative to weight loss surgery.

Testosterone replacement therapy (TRT) is prescribed to men with abnormally low testosterone which can impact their energy levels, mood and sex drive.

It is not known whether the therapy would also benefit men with healthy levels of testosterone, or what effect it would have on women.

Testosterone injections can trigger drastic weight loss in obese men, according to a German study which saw men shed an average of four stone over 10 years (stock image)

Women were not included in the study and it is also not clear how their bodies would respond, considering naturally high levels of testosterone in females are linked to weight gain, acne, excess hair growth and fertility problems.

These are the symptoms of conditions like polycystic ovary syndrome (PCOS), in which there is an increased production of testosterone, and birth disorders.

However, sometimes women are given testosterone medications to help treat the menopause, when testosterone and other hormones decline naturally.

The research, led by andrology consultant Dr Farid Saad at the pharmaceutical company Bayer AG in Berlin, was presented at this year’s European and International Congress on Obesity (ECOICO).

WHAT IS TRT?
Testosterone replacement therapy (TRT) may be prescribed if a man is diagnosed with an abnormally low testosterone.

Testosterone levels decline naturally in men as they age, but certain conditions can lead to an abnormally low level.

TRT is traditionally used to treat hypogonadism, which occurs when your testes don’t produce enough testosterone.

TRT is not normally recommended if a person has low levels of testosterone, but does not show symptoms, which may include erectile dysfunction, depression and loss of hair.

When taking TRT, men notice a difference in their energy, sex drive, and muscle mass.

Evidence shows TRT has side effects which may include:

• Acne and oily skin
• Lower sperm count, which can cause infertility
• Increased risk of blood clots
• Shrinkage of the testicles
• Larger breasts and ankles
• Increased risk of heart attack and stroke
• The US Food and Drug Administration and Health Canada have issued warnings as to the potential risks associated with TRT, while the European Medicines Agency has found no consistent evidence for such risks.

A loophole in FDA regulations allows pharmaceutical marketers to urge men to talk to their doctors if they have certain ‘possible signs’ they need treatment.

Testosterone replacement therapy is available in several forms – a skin patch, gel, injection or mouth patch.

Dr Saad said: ‘Long-term testosterone therapy in hypogonadal [low testosterone] men resulted in profound and sustained in weight loss which may have contributed to reductions in mortality and cardiovascular events. Untreated men with hypogonadism gained weight.

‘We believe testosterone therapy should be discussed with patients as an alternative to surgery and should be considered for male patients who cannot undergo surgery.’

Testosterone is the primary male sex hormone that promotes muscle growth while appearing to suppress fat gain, research shows.

Therefore men with a deficit of it may gain weight more easily.

And in a vicious cycle, being obese actually reduces levels of testosterone itself, meaning men who are already fat are likely to get bigger as their hormones change.

One study by The University of Manchester found that on average, obese men have 30 per cent lower testosterone levels than men of a normal weight.

Testosterone is made by the testicles when certain regions of the brain – the hypothalamus and pituitary glands – receive signals from the body that more of the hormone is needed.

In women, testosterone is produced in the ovaries and adrenal glands but at far lower levels, and helps maintain muscles, regulate moods and heart health.

Obesity can throw this off course and impair the signals needed to maintain average levels of testosterone.

Testosterone, which also gives the male characteristics of deep voice and hair growth, naturally declines as a man ages.

But certain conditions can lead to an abnormally low level, and sometimes there is no known cause of low levels.

The men in this study all had functional hypogonadism – low testosterone without a known ‘organic cause’, such as a deficit in their body’s ability to produce the hormone, either from the brain or the testes.

The researchers collected data from the 773 German men, around 60 years old, who were on the 2004 register of a urological practice based in Bremerhaven.

Some 471 men, almost two-thirds (61 per cent), had obesity, and of those, 276 received testosterone therapy (TRT).

They were given a 1000mg injection every three months for up to 11 years for their condition. TRT can also be given as skin patches or gel.

The other 195 men opted against the therapy, which has been linked to side effects including acne, shrinkage of the testicles and larger breasts.

Researchers analysed how their measurements changed over time, including weight, waist circumference, blood pressure and more.

The men on TRT saw their weight drop by an average of 27kg (4st 3lbs) after adjusting for other cofounders, from 18st (114kg) to 13.7st (87kg).

They lost some 13cm around their waist and their body mass index (BMI) fell by 7.6 points, from 36.8 to 28.8 – putting them from ‘severely obese’ to ‘overweight’.

But men who opted against the therapy saw their weight slightly increase by around one stone (6kg), and their waists grew by 7cm.

Their BMI – one measurement of a person’s excess weight – increased by two points.

They had more fat on their organs than those who had testosterone jabs. Called visceral fat, too much of it can lead to more health problems.

Some 63 men in this group died compared to 21 in the TRT group, the most common causes being heart attack and stroke – of which obesity is a risk factor for both.

All the deaths in the TRT group were related to traffic and sport accidents and post-surgical infections.

Astonishingly, almost every patient in the control group had type 2 diabetes by the end of the follow-up period.

At the start, 63.6 per cent had the condition, which is often caused by obesity and is therefore rising in prevalence globally.

As time wore on, a further 22.1 per cent of the men developed the condition – taking the total to 85.7 per cent.

By comparison, 56.6 per cent of those taking TRT had diabetes at the start of the study, and no more developed it over the decade.

It is not clear if TRT would have any benefit for men with a healthy weight or with normal testosterone levels, and this has not been studied before.

TRT is prescribed and given with doctor supervision, so it is unlikely it will be given for anything other than low testosterone conditions at this point.

But the researchers want to see that changed, and suggest TRT could be an effective alternative to bariatric surgery.

Bariatric surgery is considered a last option for people who cannot lose weight despite trying. It is an operation makes changes to your digestive system, such as shrinking the stomach so the person feels fuller quickly.

Although it sounds like a magic fix, it still requires a change in diet and has many risks, including gallstones, hernias, malnutrition, ulcers, and like with any surgery, the risk of infection.