A hormonal, physical, and proteomic view of obesity-induced effects on male infertility and possible lifestyle modifications

Obesity, defined by the World Health Organization (WHO) as “abnormal or excessive fat accumulation that may impair health,” is a detrimental trend that has been rising worldwide, doubling from 1980 to 2008 [1]. More specifically, the WHO estimates that more than 1.5 billion adults over the age of twenty are overweight and that 1 in 10 adults in the world are obese [1]. It has been suggested that this rising trend of excessive adipose tissue accumulation has not only been caused by an increase in high-sugar and cholesterolsaturated diets, but also by an increase in sedentary lifestyles[1]. While obesity has been associated with a host of cardiovascular disease, the metabolic syndrome, and a wide variety of endocrine abnormalities, recent research has suggested a potential link between obesity and male infertility[2]. This association has merited investigation over the past decade because of the concurrent trends of rising obesity, increasing male factor infertility, and declining semen quality[3]. Through comprehensive analysis of studies and reviews on obesity and infertility, this chapter aims to elucidate the hormonal abnormalities caused by obesity, its effect-if any-on semen parameters, and possible lifestyle modifications to alleviate the adverse effects of obesity. Ultimately, this chapter will hopefully serve as a consolidation of important and novel information on the rising concerns of obesity and male infertility. One most common tools of weight measurement used by both the WHO and researchers alike is Body Mass Index (BMI). Specifically, BMI is a ratio of an individual’s The increasing incidence of obesity worldwide combined with the parallel trend of declining sperm quality has given rise to the notion that obesity and infertility are linked. While investigations of sperm quality in obese individuals have yielded inconclusive results, studies of the adverse hormonal, physical, and proteomic changes induced by obesity are more definitive. Unfavorable hormonal abnormalities reported in obese males that affect reproduction are decreased levels of testosterone, inhibin B, and ghrelin and increased levels of estrogen, leptin, and resistin. Moreover, erectile dysfunction and elevated scrotal temperatures have been associated with obesity and are important physical barriers to successful male reproduction. Recently, important advances have been made in proteomics and factors have been identified in obese individuals that may impair spermatogenesis and sperm quality. Although obesity contributes to a host of adverse effects on the reproductive system, certain lifestyle modifications can be made to alleviate such effects. Natural weight loss and surgical weight loss have demonstrated favorable results in obese patients by restoring normal hormone levels and reversing the effects of both erectile dysfunction and testicular heat stress. Pharmacological interventions have also proven to be promising in combating the effects of obesity. Particularly, aromatase inhibitors such as anastrozole, letrozole, and testolactone, have been reported to decrease the aromatase over-activity and increased estrogen levels present in obese males. An understanding of abnormalities associated with obesity and possible lifestyle modifications may help clinicians effectively guide their infertile obese male patients and increase fertility rates. Asian Pacific Journal of Reproduction 2012; 1(2): 161-168