Is obesity a disease or a risk factor for other conditions?

Introduction

As I begin writing about obesity on my blog, I want to start by addressing a fundamental question – Is obesity a disease? Or it is primarily a risk factor for other conditions rather than a disease in its own right? What is obesity? The issue has been historically debated. The need to address this question has been warranted by the emergence of obesity as a global epidemic and its implications for health. Chronic Diseases: the Silent Killers.

Magnitude of obesity

Before we address the question, is obesity a disease? let us consider the prevalence of obesity globally. As per WHO data, worldwide obesity has tripled since 1975. In 2016, more than 1.9 billion adults, 18 years and older, were overweight. Of these 650 million were obese. In terms of percentage, these figures translate to 39% and 13% respectively, of adults aged 18 years and over. As will be discussed in subsequent posts, obesity is responsible for the growing prevalence of various lifestyle diseases. As a result, obesity has come to be regarded as “the single greatest threat to public health for this century.” More worryingly, childhood obesity has been growing at a menacing pace. As per WHO, 41 million children under the age of 5 were overweight or obese in 2016. Over 340 million children and adolescents were overweight or obese in 2016. Almost half of all overweight children under 5 lived in Asia and one quarter lived in Africa.

Is obesity a disease?

A common rhetoric, including from health professionals working in weight management centres, is that obesity is a result of ‘bad’ lifestyle choices – excessive eating and not enough exercise. However, research has documented various genetic, biological, and environmental factors that play an important role in the causation of obesity. Following recognition of factors beyond personal choice which contribute to obesity, over the years there has been a gradual movement towards acceptance of the proposition that ‘obesity is a disease.’ In the year 2013, the American Medical Association (AMA) adopted a resolution at its annual House of Delegates meeting to “recognise obesity as a disease state with multiple pathophysiological aspects requiring a range of interventions to advance obesity treatment and prevention.”

Countering the view that obesity is a personal problem of bad choices, the AMA resolution read:

“The suggestion that obesity is not a disease but rather a consequence of a chosen lifestyle, exemplified by overeating and/or inactivity is equivalent to suggesting that lung cancer is not a disease because it was brought about by individual choice to smoke cigarettes.”

The question, is obesity a disease? has been debated by many other health organisations. A number of these health professional organisations followed AMA in quick succession to recognise obesity as a disease. These included the World Health Organisation, the Food and Drug Administration, and the National Institutes of Health, USA. Finally, the World Obesity Federation, in its Position Statement published in the leading journal Obesity Reviews in Jul 2017, supported defining obesity as a disease. The statement read:

“The World Obesity Federation takes the position that obesity is a chronic, relapsing, progressive disease process and emphasises the need for immediate action for prevention and control of this global epidemic.”

To answer the question, is obesity a disease? the paper viewed obesity from an epidemiological model, with an agent affecting the host and producing disease. Food (rather than the toxic or pathological agent) is the primary agent, particularly foods that are high in energy density such as fat, or in sugar-sweetened beverages. An abundance of food, low physical activity and several other environmental factors interact with genetic susceptibility of the host to produce positive energy balance. The majority of this excess energy is stored as fat in enlarged, and often more numerous fat cells, but some fat may infiltrate other organs such as the liver (ectopic fat).

It has been argued that obesity is a disease process in the same sense that hypertension or hypercholesterolemia is a disease. Weight, like blood pressure and cholesterol, varies continuously and when each of these parameters deviates sufficiently above a mean value, it produces a disease; it is called hypertension when blood pressure is too high, hypercholesterolemia when cholesterol is too high or obesity when body fat is too high.

Why is obesity associated with so much ill-health?

Three types of ill-effects on health arise as a result of the accumulation of excess fat, including ectopic fat, in the body. Firstly, the ‘increased visibility’ (body size provides a visual read-out to the observing individual about the size of the person they are seeing) may lead to the stigma of obesity or weight bias, in children and adults, not only by the general public but by health professionals as well. This may lead to discrimination and contribute to depression and anxiety. Secondly, the excess body fat may lead to (or worsen) osteoarthritis and sleep apnea (due to the accumulation of fat in the pharynx [cavity behind the nose and mouth]). Thirdly, certain diseases develop as a result of the secretion of certain chemical substances by the enlarged fat cells and ectopic deposition of fat.

It used to be believed that fat was just an inert tissue. However, now it is evident that fat cells are a veritable endocrine factory (the endocrine system is made up of glands that produce and secrete hormones, chemical substances produced in the body that regulate the activity of cells or organs). As fat cells increase in size, they produce and secrete a variety of metabolic, hormonal, and inflammatory products. These substances and ectopic deposition of fat produce damage in organs such as arteries, heart, liver, muscle, and pancreas, which then manifest as diabetes, heart attack, hypertension and stroke, some forms of cancer, and gallstone disease.

Obesity paradox

Even though obesity has been found to be associated with a whole range of health conditions discussed above, there is a section of the obese population which does not suffer as much from the health consequences of obesity as do the rest of the population. As discussed in the preceding sections, this subset of people do not exhibit any evidence of any of the above-described health conditions or any other metabolic abnormalities despite being obese, i.e. they are metabolically healthy. This has led some people to suggest that we don’t need to be concerned about being obese and that there is nothing really wrong with carrying excess fat. This myth has been further compounded by observations in past decade that a higher BMI may be associated with lower mortality and better disease outcome in several chronic diseases and health conditions, especially in the elderly patients; these paradoxical findings have been described as “obesity paradox.”

This relationship of obesity with various metabolic disorders and health conditions has been examined in various research studies. Large number of longitudinal studies (longitudinal studies employ continuous or repeated measures to follow particular individuals over prolonged periods of time – often years or decades) have compared people who were normal weight and metabolically healthy at baseline with people who even though obese were also metabolically healthy at baseline, and followed them up for 11 to 15 years. As in the case of risk of premature death, which increases as the time period from baseline increases, in these studies also, across time, people who were metabolically healthy at baseline in spite of being obese, started to develop much greater range and risk of various cardiometabolic problems including CVDs, compared to people who were both normal weight and metabolically healthy at baseline. These findings suggest that over time it is actually impossible to escape the ill health consequences of obesity.

The ill effects of obesity develop and manifest over time; the range and degree of abnormalities increasing as the time period from baseline increases. In the interim, people may remain metabolically normal even though their weight is increasing. More importantly, as has been highlighted in the preceding sections, excess body weight or even excess body fat per se does not produce adverse health effects associated with obesity. There is a whole range of other factors that have been shown to compound the ill effects of obesity. As highlighted before, rather than the total amount of body fat, where that fat is stored is probably more important; so fat that is stored ectopically outside of fat stores, particularly within the liver or muscle, and particularly cardiac (of or relating to heat) muscle, is the one that is associated with most ill health.

In addition, a host of factors other than the total body fat and fat patterning, determine health and disease outcome. First is the body composition – higher BMI may be due to greater muscle mass (LBM) rather than fat mass, which is associated with favourable health outcomes. Nutritional status also has a significant influence on health outcomes. Finally, physical fitness, including both cardiorespiratory fitness and muscular fitness, greatly modifies the relationship of adiposity to cardiovascular and all-cause mortality. During the recent decades, many studies have provided evidence that obese subjects with an increased cardiorespiratory fitness have lower all-cause mortality and lower risk of cardiovascular and metabolic disorders and certain cancers, compared to people who are normal weight but physically unfit.

Nevertheless, the discussion over the existence of the obesity paradox should not lead to an underestimation of obesity as a crucial risk factor for the development of cardiovascular and metabolic diseases, thereby precluding doctors and patients from proper lifestyle management which is at the core of prevention of all lifestyle-related diseases. According to the report from the WHO, 2.8 million people die each year as a result of being overweight or obese.

Is obesity a disease? – Benefits of labelling obesity as a disease.

Even though a large number of reputed health organisations and institutions have recognised obesity as a disease, this recognition is not forthcoming from most of the governments – the policymakers. Several benefits will accrue if obesity is officially recognised as a disease.

1. Destigmatise obese individuals – As highlighted before, a common rhetoric is that obesity is the result of bad lifestyle choices. For some, the internalised stigma or the belief that their problems are self-inflicted and shameful can have serious psychosocial consequences. Also, such internalised stigma may itself become a barrier to effective weight loss and may impair weight loss maintenance. Recognition of obesity as a disease may free the obese individuals from this stigma.
2. Change the public discourse – As highlighted before, the public at large, including the healthcare professionals engaged in weight management, blame the individuals for their weight condition. Recognition of obesity as a disease may help remove this weight bias, encouraging greater empathy with the patients. After all, how often the blame for heart disease or cancer is put on the individual.
3. Increase the collaborative efforts to arrest the tide of obesity – The World Obesity Federation in its Position Statement argues that as infectious diseases have been effectively controlled by changes to the environment – such as improved sanitation to reduce the levels of communicable diseases, similarly the obesity epidemic could be controlled by changing the ‘obesogenic environment’. However, such changes would require collaboration between governments, health professionals, food industry, and others. Recognition of obesity as a disease could promote changes to perception and increase collaborative efforts. Removing barriers to physical activity may be considered analogous to the use of antibiotics for infectious diseases. The Position Statement further suggests that ‘early diagnosis and treatment of childhood obesity could be considered similar to vaccination, by targeting individuals from the day of birth’ – preventing diseases through proactive policy. A healthy body weight and lifestyle should be implemented from early stages of life.
4. Funding by health insurance companies – Almost all health insurance schemes, whether government funded or privately funded, limit payment for non-disease conditions like obesity, as obesity is considered to be a result of ‘failure of people to look after themselves’. Recognition of obesity as a disease could bring obesity in the ambit of health conditions eligible for health insurance coverage. This will make medical and surgical treatment accessible to large sections of the obese

Is obesity a disease? – Concerns about labelling obesity as a disease

However, there remain certain concerns about labelling obesity as a disease. These include:

1. Declare large sections of the population as ‘being ill’ – The biggest argument against classifying obesity as a disease is made on the grounds that obesity is “primarily a risk factor for other conditions rather than a disease in its own right.” Declaring obesity as a disease effectively declares large sections of the population as ‘being ill’.
2. Another concern about labelling obesity as a disease is related to the finding that some people with obesity do not have any of the risk factors for associated diseases, such as high blood cholesterol, high blood sugar or high blood pressure. This aspect has been covered under obesity paradox.
3. Divert attention from ‘personal responsibility’ – Tackling the obesogenic environment is an integral part of the treatment of obesity. However, lifestyle modification at the individual level is central to the whole process. There have been concerns in some quarters that over-medicalisation (i.e. dependence on medical and surgical procedures) may result in a slackening of efforts to change the obesogenic environment and/or individual responsibility for lifestyle modification. Also, it may lead to a greater reliance on costly drugs and surgery.

Is obesity a disease? – Conclusion

Is obesity a disease? Factors beyond ‘personal choice’ play an important role in the causation of obesity. Many of these factors are beyond individual control. For instance, changing the obesogenic environment is beyond individuals and would require government involvement. Governments can change the food environment by regulating the food industry through taxation and other measures. It can promote physical activity by regulating the ‘built environment’ by, say, for example, improving cycling infrastructure, creating facilities for leisure activities in the neighbourhood. Recognising obesity as a chronic disease will reduce the blame on individuals with obesity and push the governments and other agencies to invest in strengthening measures to reduce the obesogenicity of the environment to which the population is exposed and improve access to treatment, for obese patients.

While addressing the question, is obesity a disease? an editorial titled ‘Should we officially recognise obesity as a disease?’ published in a reputed medical journal, The Lancet, in Jun 2017, concludes – “Until obesity is universally recognised as a chronic disease, not a lifestyle choice, its prevalence is unlikely to be reduced.” Holistic Health Approaches: the Way to Wellness