HOUSTON—Lifestyle modifications that lead to weight loss may help reduce the prevalence of low testosterone levels by almost 50% in overweight, prediabetic middle-aged men, according to a new study presented at The Endocrine Society’s 94th Annual Meeting.
“Doctors should first encourage overweight men with low testosterone levels to try to lose weight through diet and exercise before resorting to testosterone therapy to raise their hormone levels,” said study co-author Frances Hayes, MD, Professor of Medicine at St. Vincent’s University Hospital, Dublin, Ireland.
The study involved 891 men with impaired glucose tolerance (IGT) from the Diabetes Prevention Program (DPP). The men were not on medications that interfere with testosterone levels. Of the 891 subjects, 293 were randomized to lifestyle modification, 305 were randomized to receive metformin, and 293 were randomized to placebo. Because overweight men are more likely to have low testosterone levels, Dr. Hayes and her colleagues studied the impact of changes in body weight and insulin sensitivity on serum testosterone levels in men. In a previous study, the researchers had shown that increasing insulin resistance was associated with a decrease in Leydig cell testosterone secretion.
The researchers analyzed anthropometric variables (body mass index [BMI], waist circumference), physical activity (metabolic equivalent hours/week), insulin sensitivity (homeostatic model assessment (HOMA-IR) and reproductive hormone levels (testosterone and luteinizing hormone [LH]) at baseline and at 12 months. Men were excluded from the study if they had a known diagnosis of hypogonadism or were taking medications that could interfere with testosterone levels. Lifestyle modifications consisted of exercising for 150 minutes a week and eating less fat and fewer calories.
The mean age of the men at baseline was 53.9 years and the mean BMI was 31.9 kg/m2. The researchers observed that the mean testosterone levels (407 ng/dL) were not significantly different among treatment groups at baseline and in the group as a whole did not change (417 ng/dL at 12 months). However, the men randomized to lifestyle modification had a 15% increase in testosterone levels (417 vs. 460 ng/dL). The researchers observed no change in LH (3.1 vs. 3.1 IU/L). Testosterone levels were unchanged in the other two treatment groups.
The overall prevalence of hypogonadal testosterone levels (below 300 ng/dL) at baseline was 23.7%. Through lifestyle modification, the prevalence of hypogonadal testosterone levels decreased from 20.4% to 11.1%, a 46% decline. The prevalence was not significantly changed in the metformin group (24.8% vs. 23.8%) and the placebo group (25.6% vs. 24.6%). Reduction in body weight was greater with lifestyle modification than metformin (-7.8 vs. -2.8 kg), as was the decrease in HOMA-IR (7.0 to 5.2 with lifestyle modification vs. 7.2 to 6.0 with metformin).
Changes in testosterone levels correlated with changes in body weight, waist circumference, and HOMA-IR. They observed no relationship between change in testosterone and physical activity levels. “We didn’t see any benefit with exercise. That surprised us. I thought that it would lead to some improvement in testosterone, but we were not able to see any relationship there,” Dr. Hayes told Renal & Urology News.
Men in the lifestyle modification group lost an average of about 17 pounds (7.8 kg) over the one-year study. “Losing weight not only reduces the risk of prediabetic men progressing to diabetes but also appears to increase their body’s production of testosterone,” Dr. Hayes said.