When levels were low, testosterone replacement led to lost weight, smaller waists

By Salynn Boyles
WebMD Health News

Medically Reviewed by Dr Farah Ahmed

10th May 2012 -- Testosterone replacement may promote weight loss in obese older men who have low levels of the male sex hormone, a new study shows.

However, before men try to lose weight by bumping up their testosterone, experts agree that more studies are needed to show that the treatment is both safe and effective.

Researchers followed a group of mostly older, overweight men receiving injections of the hormone for up to five years to treat erectile dysfunction and other symptoms associated with low testosterone.

Their findings were presented at the 19th European Congress on Obesity in Lyon, France.



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Dramatic weight loss

The men who were treated the longest lost more than 30 pounds (more than 2 stone or 13.6 kilograms) on average over the course of the study and also showed improvements in blood pressure, blood glucose and LDL (bad) cholesterol.

Researcher Farid Saad is a researcher with Bayer Pharma AG, of Berlin, Germany. Bayer manufacturers the long-acting testosterone treatment the men received. He says the dramatic weight loss came as a surprise.

"This study was not performed for the purpose of promoting weight loss," he tells us. "This was an incidental finding that was entirely unexpected."

Low testosterone common in obese men

The study included middle-aged and older overweight or obese men with low testosterone levels being treated with testosterone replacement at a single urology clinic.

A total of 214 men remained in the study for at least two years and just over half of these men were followed for another three years or more.

All the study participants received a long-acting injected testosterone, with two injections given during the first six weeks of treatment followed by injections every three months as long as they remained in the study.

Men who were treated the longest lost the most weight and saw the biggest reductions in waist circumference and body mass index (BMI).

After five years of follow-up, the average weight loss was 2.5 stone (15.88 kilograms) and the average waist circumference dropped from about 42 to 38 inches (106.7 to 96.5 cms). Most men also saw improvements in triglyceride levels, blood pressure, blood sugar and LDL cholesterol.

Testosterone for weight loss: 'More study needed'

Dr Farid Saad says they may have lost weight on the testosterone therapy because they had more energy to exercise.

"This is a theory, and, certainly, more research is needed to confirm our findings," he tells us.

There are concerns that prolonged testosterone therapy could increase the risk of prostate cancer but there was no evidence of this among the men in the study.

Last resort

Professor Richard Sharpe from the University of Edinburgh Centre for Reproductive Health, is convinced that keeping an ageing man's testosterone levels up in the 'normal' range is arguably one of the most important health-beneficial things that should be done. However, in an e-mail he says he has concerns about how best to do this and says resorting to pharmaceutical intervention should be the last resort.

"The issues are (1) who needs treatment, and (2) what are the trade-offs, such as increased risks of prostate disease and/or perhaps cardiovascular disease (one study has suggested). So the notion that this is a quick fix for obese older men is, as always, simplistic. It is far far far more sensible (and safe) for the men to reduce their food intake, reduce their obesity which will then elevate their own testosterone� (without any risks and with multiple benefits).

"Indeed, if I had one piece of advice to give to aging men (and indeed, increasingly to young men) it is to reduce your intra-abdominal fat to conserve your decreasing testosterone levels. It will prolong your life, protect you from the common Western diseases AND conserve your testosterone (which is associated with greater energy levels and of course greater sex drive/libido)."

The latest study findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinise the data prior to publication in a medical journal.