Why Obesity Should Be Classified a Disease

One reason that obesity should be classified as a chronic multifactorial disease is due to the complex multifactorial aetiology causing a chronic progressive disease. For decades, there has a been a large debate regarding whether obesity is caused by eating behaviour or the obesogenic environments which reduces individuals levels of physical activity. However, these factors work alongside strong overwhelming biological, metabolical, genetic and psychological factors which lead to the complexity of obesity. Obesity develops over time through an imbalance between energy consumption and energy expenditure, therefore excess energy is deposited in fat cells which causes weight gain. Attributing the cause of obesity to the imbalance of the energy system from overeating and a lack of physical activity is over simplistic, and fails to acknowledge that obesity is caused by large multifactorial factors, leading to the development of a chronic disease.

Firstly, environmental agents cause an imbalance of the energy system include increased food intake which is increased due to the obesogenic environment which is the mode rn environment whereby eating energy dense foods with high sugar and high fat is encouraged (Chaput et al., 2011). Additionally, chemicals such as as phthalate and bisphenol are often found in the environment and are associated with obesity through disrupting the metabolism. This indicates the environmental factors which are associated with obesity.

There are a number of behavioural agents which cause obesity through effecting the energy imbalance system by influencing increased eating behaviours, such as emotional eating in which individuals use food in response to their emotions (Fischer et al., 2007), prescription of antidepressants such as mirtazapine (Chandra et al., 2018) and antipsychotics such as clozapine, quitting smoking and low physical activit. For example, low participation in physical activity increases sedentary behaviour which imbalances the energy system by reducing the energy expended.

Psychological factors are largely comorbid with weight gain, with large associations between depression and obesity (Blaine, 2008) with large links to eating behaviours such as depression increasing emotional eating and calorific intake.

There are large metabolic factor which imbalance the energy system through disordering signalling for hunger, satiety and fullness, which are not fully understood. For example, a number of peripheral peptides have been shown in research to induce satiety signals in the brain, which examples of these peptites are leptin, cholecystokinin (CCK), glucagon-like peptide-1 and peptide YY (PYY) which when disordered, they increase food intake (Geliebter, Ochner & Aviram-Friedman, 2008). Most importantly, leptin binds to receptors in the brain which controls food intake, some may be genetically predisposed to leptin deficiency, which medites the energy balance system. Some individuals have a dysregulation of leptin or a mutation on the leptin receptor, abnormalities in the proopiomelanocortin gene (POMC) or in the melanocortin-4 receptor system.

Various genes have been identified that contribute to obesity, for example genetic variants of the fat mass and obesity-associated gene (FTO) predisposes changes in BMI and body weight which leads to obesity (Frayling et al., 2007). Additionally, genome wide studies have found 58 genes contributing to obesity which identifies the role of genes involved in the genetic predisposition of obesity.

All of these factors alter the energy system, and lead to characteristics which are identifiable with obesity which deviates from normal structure and these changes can predispose obese individuals to be susceptible to dyslipidaemia, hypertension, hyperinsulinemia and diabetes. The predominant sign of obesity is excess accumulation of fat or adipose tissue, which in turns increases an individual’s BMI.

This evidence indicates why it is important to recognise obesity as a multifactorial disease as similar to other diseases, it meets a medical disease criterion. Not only this, but evidence has shown that it is a risk factor for other diseases, therefore the complexity of obesity is congruent with a disease, therefore having a classification as a chronic multifactorial disease will improve access to prevention and treatment programmes.