This content was originally posted on athleticlab.com.
The United States has inarguably been one the hardest hit countries in the world by COVID-19. While the reasons for this is undoubtedly multi-factorial, an often overlooked confounding issue is the state of our nationwide health. In this guest post, Gaby Smith presents the compelling science on why COVID-19 and obesity are such a deadly combination.
[This is a guest blog by Gaby Smith. Gaby Smith completed her MS in Exercise Science at Northeastern University and is participating in the Athletic Lab Mentorship Program. Gaby is a Certified Strength and Conditioning Specialist and holds certifications with U.S. Soccer, USAW, and USTFCCCA.]
In the United States, we find ourselves in the midst of two epidemics: COVID-19 and obesity. While initially the two may seem to be only tangentially related, numerous studies have found a significant association between BMI and risk for death among COVID-19 patients independent of related health conditions (diabetes, hypertension, coronary artery disease) (Tartof et al., 2020). This association is of particular concern in the United States, as over 40% of the population is considered obese (BMI >30 kg/m2) (Kass, 2020).
To this point, the two primary strategies to slow the spread of COVID-19 include mitigation (handwashing, wearing a face covering, social distancing) and the adoption of practices consistent with good overall health. COVID-19 is primarily transmitted through airborne droplets when infected individuals cough, sneeze, talk, or breathe deeply. Inhaled droplets infect cells lining the airway and cause modest symptoms including coughing, fever, shortness of breath, fatigue, and loss of taste or smell, among others (CDC, 2020).
Why is obesity such a significant risk factor?
Obesity seems to increase the severity of COVID-19 cases as a result of the chronic inflammation that characterizes obesity and causes metabolic and immune derangement (Korakas et al., 2020). Obese populations have chronically higher levels of leptin (which has inflammatory effects) and lower levels of adiponectin (which has anti-inflammatory effects) (Luzi and Radaelli, 2020). Higher levels of adipose tissue also lead to defective immune function and altered immune activation in the presence of antigens. Obesity not only inhibits the cells’ response to viral agents, but the dysregulated pro-inflammatory response also contributes to the increased severity of illness observed in this population (Luzi and Radaelli, 2020).
Another reason this population tends to experience more severe respiratory illness is their lack of physical inactivity. Both physical activity and exercise have been shown to increase the immune response and help facilitate positive outcomes in both metabolic and immunological health (Luzi and Radaelli, 2020). These individuals may also have decreased respiratory capacity or difficulty breathing, further worsening the respiratory symptoms associated with the illness.
Obese individuals also tend to be more contagious than leaner populations. These patients shed the virus for up to 104% longer than leaner subjects, potentially increasing their likelihood of spreading the virus (Luzi and Radaelli, 2020). Because of the dysregulated and delayed immune response, these individuals also tend to produce more virulent strains of the virus, as the virus is able to replicate for a longer period of time. Further, BMI has been found to be positively correlated with increased infectious virus exhaled per breath. This is likely due to the combination of higher ventilation volumes and viral loads observed in this population (Luzi and Radaelli, 2020).
In short, obesity and physical inactivity lead to increased systemic inflammation, decreased immune function, decreased viral defense, and potentially inefficient ventilatory capacity (Nieman, 2020).
So can I reduce my risk?
Diet and physical activity are essential preventative measures to improve defense against severe COVID-19 infection and are important aspects in maintaining good overall health. Not only do diet and exercise aid in weight management, but they also improve immune function. Regular moderate-intensity physical activity has been shown to improve immune function and reduce morbidity and mortality from viral infection (Nieman, 2020). Physical activity not only improves the early immune response, but also affects energy balance, leptin response, and antibody production which all are essential in protecting from infection (Luzi and Radaelli, 2020).
Regular aerobic exercise improves immune function by stimulating the exchange of white blood cells and infection-fighting cells, while also keeping stress hormones and inflammatory responses low both during and in the hours following exercise (Nieman, 2020). When performed regularly, exercise increases antipathogenic cells which enhance immunity and reduce illness risk. Clinical studies have shown that engaging in near-daily aerobic activity can reduce illness days stemming from respiratory infections by 40-45% when compared to sedentary lifestyles in both younger and older adults (Nieman, 2020). The severity and symptomatology of the illness were also reduced by 32-41% in those engaging in aerobic activity, indicating that physical activity can both reduce the duration and severity of respiratory illnesses. In addition to having positive effects on the immune system, regular physical activity improves cardiovascular function and protects against cellular stress, as well as improving the endurance, strength, and efficiency of respiratory muscles (Jakobsson et al., 2020).
But my gym is closed … how can I remain physically active?
Mandatory stay at home orders, the closures of gyms, and enforcement of other mitigation strategies have made physical activity difficult for many. While remaining physically active may be more challenging in the midst of the COVID-19 pandemic, it may be more important than ever. In addition to enhanced immunity, exercise may prevent weight gain, increase metabolic rate, reduce stress and anxiety, and improve sleep. The American Heart Association recommends adults perform at least 150 minutes of moderate intensity or at least 75 minutes of vigorous intensity exercise every week.
While going to the gym is one of the more obvious ways to remain physically active, there are many “socially distant” means of physical activity that do not require a gym and are not affected by the forced closure of gyms or other fitness facilities. Getting outside and walking, biking, jogging, or hiking are all great ways to stay safe, get fresh air, and safely distancing oneself from others. There are also online videos, training sessions, and live virtual classes offering many different types of exercise classes that are easily accessible and can be performed from home. Also, simply remaining active by doing chores like mowing the lawn, washing the car, or cleaning the house are low-intensity and simple ways to remain active while at home.
Obesity is a health risk under the best of circumstances. But in the presence of a global pandemic the risks are even greater. The effects of this deadly combination are especially stark in the United States where our population already suffers from high lifestyle related health issues.
- In the United States, over 40% of the population is considered obese (BMI >30 kg/m2)
- Obesity increases the risk of severe COVID-19 symptoms and complications independent of other comorbidities or conditions
- Obesity and physical inactivity decrease immune function, create systemic inflammation, decrease ventilatory capacity, and decrease viral defense leading to an increased viral load in these subjects
- Physical activity is a critically important preventative measure (even if your gym is still closed!) to maintain and improve immune function and cardiorespiratory capacity
- All physical activity is beneficial (walking, running, biking, hiking, virtual classes/videos)
- Aim for at least 150 minutes of moderate intensity or 75 minutes of vigorous activity per week.
- Nieman, D. C. (2020). COVID-19: A tocsin to our aging, unfit, corpulent, and immunodeficient society. Journal of Sport and Health Science.
- Kass, D. A. (2020). COVID-19 and Severe Obesity: A Big Problem? Annals of Internal Medicine. doi:10.7326/m20-5677
- Tartof, S. Y., Qian, L., Hong, V., Wei, R., Nadjafi, R. F., Fischer, H., . . . Murali, S. B. (2020). Obesity and Mortality Among Patients Diagnosed With COVID-19: Results From an Integrated Health Care Organization. Annals of Internal Medicine. doi:10.7326/m20-3742
- Korakas, E., Ikonomidis, I., Kousathana, F., Balampanis, K., Kountouri, A., Raptis, A., . . . Lambadiari, V. (2020). Obesity and COVID-19: Immune and metabolic derangement as a possible link to adverse clinical outcomes. American Journal of Physiology-Endocrinology and Metabolism, 319(1). doi:10.1152/ajpendo.00198.2020
- Jakobsson, J., Malm, C., Furberg, M., Ekelund, U., & Svensson, M. (2020). Physical Activity During the Coronavirus (COVID-19) Pandemic: Prevention of a Decline in Metabolic and Immunological Functions. Frontiers in Sports and Active Living, 2. doi:10.3389/fspor.2020.00057
- Luzi, L., & Radaelli, M. G. (2020). Influenza and obesity: its odd relationship and the lessons for COVID-19 pandemic. Acta diabetologica, 57(6), 759–764. https://doi.org/10.1007/s00592-020-01522-8