Obesity has become one of the most worrying global pandemics. According to a previous comprehensive study, there was an exponential increase in the incidence rate of overweight and obesity during the last 30 years. Almost one third of the world’s population are either overweight or obese in terms of body mass index (BMI). The BMI is calculated as weight in kilograms divided by the square of height in meters; where a person with BMI ≥ 25 is considered to be overweight, while BMI ≥ 30 indicates obesity. The World Health Organization (WHO) reported that more men than women were classified as overweight or obese in developed countries, whereas the opposite was true in developing countries. Overall, the highest prevalence of overweight and obesity is found in the WHO regions of the Americas, as recent reports estimated 20% of children in the United States as obese.
Although obesity is associated with many serious health problems, a new research highlight published in the journal BMC Medicine has linked the global prevalence of obesity to the parallel rise of male breast cancer (MBC). It might sound strange, however, MBC was first reported in medical literatures in 1843 as the disease that killed five men in Paris from 1830 to 1840. Currently, WHO estimated the global incidence of MBC to stand at 8,000 cases. New studies suggest that black men are more susceptible to MBC than white men which represents a racial disparity, but other factors, such as genetic background and socioeconomical status, can affect MBC distribution.
The authors of the study, Dr. Matthew Humphries and Dr. Valerie Speirs at University of Leeds, stated that “Though not officially recognized as a risk factor for MBC, obesity has been highlighted by several studies as being significantly associated with MBC”. To further narrow down and dissect the relationship between obesity and MBC, the authors referred to one of the common characters of adipose tissue in producing estrogen. Adipose tissue, commonly known as fat cells, contains aromatase which converts the male hormone testosterone to estrogen. Such conversion and subsequent disturbance in hormonal levels create a favorable microenvironment for MBC initiation. Also the increase in fat cells leads to suppression of luteinizing hormone which is responsible for testosterone stimulation, and hence restricts the availability of testosterone. As a result, obese older men will have more estrogen than post-menopausal women.
Another line of evidence comes from studying the cholesterol metabolism in the context of obesity. Cholesterol is converted into another metabolite called 27-hydroxycholesterol (27HC) that binds to estrogen receptor and induces more cellular proliferation in case of breast cancer. As a rule of thumb, circulating levels of 27HC correlate with cholesterol levels in obese patients that also reflect bad nutritional habits.
Generally, men with MBC have worse prognosis and shorter survival time than women with breast cancer. The time of detection is considered as a critical factor in case of MBC and usually men get diagnosed with MBC in later stages of the disease. Insufficient awareness of MBC added to possible public embarrassment in seeking medical consultation might aid to such worse conditions.
The authors concluded that the changes in nutritional habits over the past decades have shifted the average body weight towards a more obese/overweight state that requires more public attention and regular visits to GPs than before.