BOSTON — Healthy men with obesity and low testosterone randomly assigned testosterone therapy combined with a very low calorie diet maintained their muscle mass while losing body fat, whereas men assigned placebo lost both lean and fat mass, according to study findings presented here.

“Men who adhere to a very low calorie diet lose significant weight, and they lose fat mass, which is great, but they also lose lean mass, which may not be desirable,” Mark Ng Tang Fui, MBBS, BMedSc, FRACP, an endocrinologist and PhD student in the department of medicine at the University of Melbourne in Victoria, Australia, told Endocrine Today. “So if we also treat these men with testosterone, this helps these men to maintain their lean mass, and they lose more fat mass.”

Fui and colleagues analyzed data from 100 men with a BMI at least 30 kg/m² with serum total testosterone levels less than 12 nmol/L (mean age, 53 years; mean baseline BMI, 37.4 kg/m²; mean baseline fat mass, 45.1 kg; mean baseline testosterone, 7.1 nmol/L). All men were assigned a very low calorie diet for 10 weeks (approximately 600 kcal daily), followed by a weight maintenance diet with normal foods for the next 46 weeks. Researchers randomly assigned participants to 10 weekly 1,000-mg intramuscular testosterone injections (n = 49) or placebo injections (n = 51) for 56 weeks. Primary outcome was fat mass as measured by DXA scan; visceral fat mass via abdominal CT scan and lean body mass via DXA were secondary outcomes.

At 56 weeks, both groups lost approximately 11 kg; however, researchers found men in the testosterone group lost more fat mass (mean absolute deviation, -2.9 kg) and visceral fat (MAD, -2,678 mm²) compared with men assigned placebo. Testosterone therapy also prevented diet-associated loss of lean mass and muscle function (MAD, 3.4 kg).

Fui cautioned that the cohort consisted of relatively healthy men motivated to lose weight with frequent monitoring and that the study did not include an exercise arm and was not designed to evaluate metabolic outcomes.

“While men on placebo lost both lean and fat mass, testosterone prevented this loss of lean mass and shifted the weight loss almost exclusively to loss of fat,” Mathis Grossman, MD, PhD, FRACP, associate professor in the department of medicine at the University of Melbourne in Victoria, Australia, told Endocrine Today. “We now want to see whether these changes, expected to be metabolically favorable, safely translate into improved cardiometabolic outcomes.” – by Regina Schaffer


Ng Tang Fui M, et al. LB-OR02-1. Presented at: The Endocrine Society Annual Meeting; April 1-4, 2016; Boston.

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