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Obesity and Male Fertility

A blog by Dr. Matthew Wosnitzer
October 15, 2014

Negative effects of obesity have been described since the time of the ancient Greeks. Obesity is defined by abnormal fat accumulation with body mass index (BMI) ≥30 kg/m2 and results from energy imbalance (too much energy consumed). Obesity, currently reaching epidemic proportions worldwide, carries increased risk of metabolic syndrome (a combination of abdominal obesity, diabetes mellitus, hypertension, elevated triglycerides/cholesterol), cardiovascular disease, fertility issues1, testosterone deficiency, depression, sleep apnea, and reduced quality of life and early death. Declining sperm counts have been identified in some studies to be present among countries with higher obesity rates, while not identified in countries with lower obesity rates2. Further if obesity affects the woman in addition to the male, then subfertility issues are worse than just one partner being obese. However, we will focus on the effects of obesity on male fertility.

In terms of fertility, obesity leads to negative effects in both men and women. In women, effects of being overweight or obese may alter menstrual function3. In men, effects on fertility are less obvious than in women but may result in reduced sperm concentration possibly a 20% reduction in some studies4. In addition to reduced sperm count (oligospermia), azoospermia (no sperm in ejaculate)5, abnormal motility or morphology, and/or impaired DNA integrity (measured by DNA fragmentation index)6,7 have also been described. In fact, the proteins expressed in the sperm of obese men are known to differ from non-obese men8. While many population-based studies show this effect9,10,11 from the United States and Europe, others do not show negative effects on sperm.

Overall, summaries of available studies including a meta-analysis (summary of 21 studies including over 13,000 men) on this topic12, conclude that obesity increases risks of deleterious change to semen parameters13 and may affect fertility of the couple14,15,16 with maximal effect with a male partner’s BMI between 32 and 43 kg/m2. Further, men in infertile couple populations often, but not always show a relationship between obesity and male infertility17.

Obesity affects sperm production and function by leading to abnormal hormone levels, increased scrotal temperatures, and inflammatory markers (such as adipokines) produced by fat cells18. In addition to these factors, genetics (including Praeder-Willi and Klinefelter syndrome) may contribute to obesity and whether or not men are fertile19,20. Further lack of leptin production or leptin resistance (with increased leptin levels) may be associated with obesity and infertility given that leptin can suppress the hormonal production from the brain and receptors are present in both testis and on sperm outer surfaces21,22,23.

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