Leaf through any magazine dedicated to health and wellness, whether its intended audience is the general consumer or a medical professional, and you will invariably come across an article whose focus is some obesity related health condition. The CDC considers obesity an epidemic responsible for a host of chronic diseases affecting every major organ system of the body, and the male reproductive system is not immune. Over the last couple of years, researchers have linked obesity to several factors causing male infertility.
Obesity is an endocrine disrupter resulting in lower levels of reproductive hormones that are critical to spermatogenesis, the development of sperm cells. Spermatogenesis requires sufficient testosterone and properly functioning Sertoli cells, which provide physical and nutritional support to developing sperm cells. Luteinizing hormone (LH) stimulates testosterone production, which in turn stimulates sperm cell maturation under the “care and protection” of Sertoli cells. Follicle stimulating hormone (FSH) and Inhibin B regulate the function of Sertoli cells. Sub-optimal levels of any of these four hormones will lead to fewer mature sperm cells and a lower sperm count, and researchers have linked obesity to lower levels of all four. They are exploring the possibility that elevated insulin levels, a hallmark of metabolic syndrome, is a factor in the dysregulation of these reproductive hormones. (Metabolic syndrome is a group of risk factors, brought on by obesity, that increase an individual’s risk for cardiovascular disease and type-2 diabetes. These risk factors are high blood pressure, abnormal cholesterol levels, high blood sugar, elevated insulin levels, and excessive abdominal fat.)
Obesity has been linked to a higher level of sperm oxidative stress. Oxidative stress is the damage caused by free radicals reacting with molecules in an organism. This happens when physical and environmental changes occur that prevent antioxidants from reacting with, and thus eliminating, these free radicals. Oxidative stress damages the molecular composition of sperm. It compromises DNA integrity and decreases the acrosome reaction. The acrosome reaction occurs in the head of sperm and involves the release of enzymes that enable sperm to penetrate an egg. Oxidative stress is also implicated in decreased motility and disrupted cell signaling (communication). All these factors impair the ability of sperm to fertilize an egg.
The development and maturation of sperm is highly sensitive to heat. The presence of excessive fat around the testes elevates the temperature in the testes to damaging levels, reducing the amount of mature sperm produced. Higher gonadal temperatures also contribute to sperm oxidative stress.
Some of the most recent and quite possibly most disturbing research findings involve obesity and epigenetic inheritance. Epigenetic inheritance involves changes in gene expression, as opposed to physical changes to the genes themselves. Scientists are studying the link between obesity in fathers and reproductive and metabolic disturbances in their children. Studies are being conducted on rats and mice that show a strong correlation between paternal obesity at the time of conception, and fertility and metabolism disorders in offspring. Altered methylation of sperm DNA and damage to sperm RNA from oxidative stress are being explored as possible culprits.
If you are an overweight male who is having trouble achieving a pregnancy with your partner, all is not lost. Each of the outcomes described above can be improved with weight loss, proper nutrition, and exercise. Considering the devastating impact obesity has on all major organ systems, weight loss will not only be an investment in your future fertility, but also an investment in your future health and well-being.
Palmer NO, Hassan WB, Fullston T, Lane M. Impact of obesity on male fertility, sperm function and molecular composition. Spermatogenesis. 2012; 2(4): 253-263.
McPherson NO, Fullston T, Hassan WB, Setchell BP, Lane M. Obese father’s metabolic state, adiposity, and reproductive capacity indicate son’s reproductive health. Fertil Steril. 2014; 101(3): 865-873.
Hammoud AO, Wilde N, et al. Male obesity and alteration in sperm parameters. Fertil Steril. 2008; 90(6): 2222-2225.0