Obesity in respiratory patients: reflecting on the evidence

It is now well established that obesity is more detrimental to health than smoking, heavy drinking or poverty.[1]

While some respiratory disorders, such as obstructive sleep apnoea and obesity hypoventilation are discernibly attributable to obesity, there are also subtle links to other respiratory conditions that if not addressed can lead to the wrong diagnosis and incorrect treatment of individuals.[2]

Many of us are quite happy to address smoking with our respiratory patients, however there is still a reluctance to actively address issues surrounding a patient’s weight. If we don’t, we are missing an opportunity to really make an impact on patients’ lives, and reduce the burden of symptoms.

Obesity is defined as a body mass index (BMI) of over 30, but even being overweight adds to the burden of disease and may contribute to the development of other chronic conditions.[3] What’s more, obesity is not just about BMI, it is also about the distribution of fat within the body, with android obesity (where fat distribution is distributed around the upper body) more likely to have a more direct effect on pulmonary mechanics.[4]

The effects of body fat

As our body fat percentage increases, so does the work of breathing.[4]

If a person carries extra body fat, especially around the abdomen and on the chest wall, the diaphragm is pushed up and becomes less effective whilst also reducing the volume of the lungs.[4] This reduces the amount of air we can get in and out of the lungs which can cause breathlessness as well as wheeziness, as the airways are compressed. This could lead to the misdiagnosis of asthma or chronic obstructive pulmonary disease (COPD).

Respiratory muscle strength also deteriorates in obese individuals, and is thought to contribute to extra oxygen demands for ventilation and heightening the symptom of breathlessness often on exertion but in extreme cases with minimal movement.[5] This means that for some individuals there is an increase in the mechanical work of breathing, hence the breathlessness.[6] The airways can then become compressed as there is less capacity for bronchodilation and this can reduce the expiratory flow.[6]

Breathlessness in itself can be distressing and uncomfortable for individuals. For these reasons, they may make lifestyle adaptations such as being more sedentary. This can further compound the problem.

Asthma and obesity

People presenting with breathlessness and wheezing are often thought to have asthma and treated as such, hence the importance of a thorough history and diagnostic workup.[7]

However, there is an independent link between obesity and asthma with the prevalence of asthma higher in overweight individuals by 38% and by 92% in the obese.[8] In obese asthma patients, there is less response to therapies, which is thought to be because this population were not involved in the original studies – there is also almost a fivefold risk of hospitalisation due to exacerbations.[9]

There is a relationship between BMI and asthma, suggesting that asthma risk increases further as body weight increases.[9] However, it’s not been determined whether people with asthma are more likely to be obese, or whether obese people are more likely to develop asthma.

Weight loss is therefore likely to have a positive effect on the respiratory symptoms caused by obesity and may also have disease modifying effects.[10]

We need to be comfortable addressing this with our patients in a non-judgemental, empathetic but constructive manner. We should look to support them with lifestyle changes that have the potential to impact on their symptoms, quality of life and their respiratory conditions.

Any advice given and opinions expressed in this article are those of the author and do not reflect the view of Chiesi Limited (Chiesi).  All content in this article is for informational and educational purposes only.  Although Chiesi strives to always provide accurate information, it is not responsible for and does not verify for accuracy any of the information contained within.

[1] Sturm R, Wells KB. Does obesity contribute as much to morbidity as poverty or smoking? Public Health, 2001; 115: 229-235.

[2] Shetty S, Parthasarathy S. Obesity Hypoventilation Syndrome. Curr Pulmonol Rep. 2015; 1;4(1): 42-55.

[3] World Health Organisation. Obesity. Available at: https://www.who.int/health-topics/obesity

[4] Dixon AE, Peters U. The effect of obesity on lung function. Expert Rev Respir Med. 2018; 12(9): 755-767

[5] Zammit C, Lidicoat H, Makker H. Obesity and respiratory diseases. Gen Med 2010; 3: 335-343

[6] Salome C, King G, Berend N. Physiology of obesity and effects on lung function. J Appl Physiol 2010; 108(1): 206-11

[7] Cetlin A, Gutierrex M, Bettiol H et al. Influence of asthma definition on the asthma-obesity relationship. BMC Public Health 2012; 12: 844

[8] Beuther DA, Sutherland ER. Overweight, obesity, and incident asthma: a meta-analysis of prospective epidemiologic studies. Am J Respir Crit Care Med. 2007; 175(7): 661-666

[9] Pradeepan S, Garrison G, Dixon A. Obesity in asthma: approaches to treatment. Curr Allergy Asthma Rep 2013; 13: 434-42

[10] Juel CT, Ali Z, Nilas L et al. Asthma and obesity: does weight loss improve asthma control? a systematic review. J Asthma Allergy. 2012; 5: 21-26