Factors in the Onset of Obesity – An American Public Health Crisis

Introduction:

Obesity is one of America’s greatest public health concerns. For both children and adults, rates of obesity have generally been on the rise since 1980 (Hales et al., 2018). In 1980, 4.8% of men and 7.9% of women were obese; in 2008, those values had doubled to 9.8% and 13.8%, respectively (Carallo, 2011). More recently, as of 2018, about 42% of American adults were obese and as of 2016, about 18.5% of American children were obese (CDC, 2020; CDC, “Childhood Obesity Facts,” 2019).

It is well understood that obesity impairs both the mental and physical health; accordingly, obese individuals are estimated to have 30% more medical expenses than their non-obese counterparts. In 2006, obesity-related medical costs accounted for about 40% of the entire American healthcare budget. In addition, obesity causes significant drops in productivity – annually, obesity-related absenteeism in the workplace for each individual obese worker costs between $79 dollars and $132 dollars, accounting for billions of dollars of the total American economy (Çakmur, 2017). Given both the healthcare and productivity costs, it is clear that obesity presents a large economic burden on a national scale. And, with trends showing that obesity levels are only on the rise, it is crucial to understand the determinants for and risk factors of obesity in order to try to curb its growth.

From a medical standpoint, obesity is a serious issue. Individuals with obesity can have insulin resistance and are at higher risk for Type II diabetes (Barnes 2011). They are at risk for several cardiovascular conditions, including hypertension and coronary heart disease, and often have high cholesterol. They also often have respiratory complications and have lower vital and total lung capacity, along with the possibility of sleep apnea. Obese individuals have significantly higher chances of developing cancer and arthritis. Skin disorders, like intertrigo and eczema, are common. Furthermore, obese individuals are three times more likely to die prematurely than their non-obese peers (Ogunbode 2009).

On a biological level, the mechanism of obesity is not completely understood. Interestingly, however, it has become increasingly clear over the past years that obesity is not just a biological disorder. The growing prevalence of obesity is driven by external factors. In addition to health behaviors, there are clear disparities due to geography, socioeconomics, and race and ethnicity that are correlated with obesity. These make the obesity epidemic difficult to stop, as each factor is complex in its own way and requires different treatment by public health professional. This paper aims to comprehensively review both what is known about obesity from a medical perspective and each of the external factors; the hope is that a better understanding of the obesity crisis will allow public health experts to research and implement more nuanced solutions to the problem.

Obesity Overview:

There has been much debate within the scientific community about the classification of obesity given that it has determinants that are not solely biological. As such, many argue that obesity should be labeled as a behavioral abnormality. Nonetheless, many renowned medical foundations, including the American Medical Association, have chosen to classify obesity as a disease: as such, obesity refers to the condition where a person has a Body Mass Index (BMI) of over 30 (Stoner & Cornwall, 2014). The biological mechanisms underlying the accumulation of fat that characterizes obesity are still unknown. There are several proposed ideas, but two mechanisms seem to hold the most support.

The first of such mechanisms is genetic. Estimates vary, but various studies show that high BMI has between a 40% and 70% chance of being inherited. Both monogenic (characteristics arising from a single gene types) and polygenic (characteristics arising from multiple gene types) forms of obesity have been explored. On the monogenic side, researchers have been able to implicate mutations in leptin and melanocortin-4 receptor genes. Both play critical roles in energy homeostasis (which is further explored in the next paragraph); leptin is a hormone that inhibits hunger, and melanocortin-4 receptor binds several agonists, many of which also lead to hunger inhibition. On the polygenic side, several combinations of over 300 genetic loci have been marked as significant in resulting in obesity. Epigenomic research on obesity is ongoing and may reveal further genetic influences on obesity (Heymsfield & Wadden, 2017).

The second proposed idea is dysregulation in energy homeostasis mechanisms. Energy homeostasis refers to the balance of consumption and burning of calories. There are two main processes thought to be involved in energy homeostasis’s contribution to obesity, the first of which is sustained positive energy balance – this refers to a state in which a person is overconsuming calories while not expending enough for a long period of time. The second is resetting of the set point of body weight for a higher weight – for some reason, the body may choose to accept a higher weight as the “normal” body weight. This second process would explain why obese individuals cannot reduce their caloric intake easily and why even those who lose weight often regain it. The reasoning for this reset of weight set-point is not known currently and could be inherited or arise due to some biological or environmental trigger. A combination of both of energy processes would lead to a buildup of excess weight, and eventually to obesity (Schwartz et al., 2017).

Overall, it is clear that obesity onset is extremely complex and due to a variety of biological factors. More research into both genetic and energy-related reasons will elucidate more specific mechanisms underlying obesity in the future. However, the biological factors cannot be divorced from external determinants, including behavior, geographical location, and demographics.

Behavioral Drivers of Obesity: