Eyewitness News anchor Ken Rosato has more.
Sixty-five year-old Henk Vonk says he can tell his testosterone levels have gone down with age.
"I'm not so strong and fast anymore," he said.
Low testosterone can result in a loss of strength, mental function and bone mass.
"With this study, we want to investigate if it was possible with the testosterone to prevent the signs and symptoms of aging," Dr. Marielle Emmelot-Vonk said.
Dr. Emmelot-Vonk, who is Henk's daughter, and her colleagues at University Medical Center Utrecht in the Netherlands were among the researchers who studied six months of testosterone supplementation in older men.
The findings appear in the Journal of the American Medical Association.
"The fat mass in the body decreased and the lean mass increased, and also the insulin sensitivity improved a bit," Dr. Emmelot-Vonk said.
Dr. Yvonne van der Schouw says that's the good news. But the bad news is that HDL, or good cholesterol, decreased in the men taking testosterone.
"We would have hoped maybe to see a decrease of intra-abdominal fat, because that is the really harmful fat in the body," Dr. van der Schouw said.
But they didn't see that fat decrease. In fact, researchers did not see enough improvements to be able to recommend testosterone.
So what can men do to combat the effects of aging?
Doctors say it is important to eat healthy food and do a lot of activity.
Henk says he wishes taking testosterone had been the answer to aging.
"To be healthy, I make a walk every day and I go to the gym," he said.
Click here for more on the study.
