Physical Activity, Obesity, and COVID-19: What can we Expect from his Relationship?

apnea syndrome, acute respiratory distress syndrome, and being overweight. 10 Obesity is associated with a decrease in functional capacity, as well as with a compliance of the respiratory system and the expiratory reserve volume. 11 In France, data from patients that made use of invasive mechanical ventilation have shown that individuals with severe obesity (BMI ≥ 35Kg/m²) presented impaired respiratory patterns in relation to the patients with BMI ≤ 25Kg/m². 12 In this scenerio, obesity represents an independent risk factor for the respiratory hypoventilation syndrome, a potential aggravating factor for complications related to respiratory insufficiency in patients who are admitted to intensive care units. 13 Beyond respiratory complications, another liaison with COVID-19 is inflammation. Obesity causes an increase of secretion of pro-inflammatory cytokines in the adipose tissue, which can worsen if infected by COVID-19. 10,11,14 High serum levels of interleukin-6 (IL-6) have been reported in patients who passed away

To date, there is no pharmacological treatment that has proven to be effective, or a vaccine for the prevention or treatment of COVID-19. Thus, a non-pharmacological strategy of public health, which has shown effectiveness in the exponential control of the disease, is social distancing, which encompasses the isolation of cases, quarantine of contacts, and the voluntary practice of not going to crowed places. 3 These measures have demonstrated that they can reduce mortality rates during the pandemic, and they have helped in governmental decision-making. 3,4 Although the lethality rate of COVID-19 varies among countries, mortality most commonly occurs among the elderly or people with comorbidities, such as cardiovascular diseases, diabetes, cancer, and chronic pulmonary diseases. 5,6 In a recent study in the city of Wuhan, China, obesity was not reported as a pre-existing comorbidity, which favored the increase in the general lethality rate in patients with  However, a study conducted in New York pointed out that approximately 41.7% of all hospitalized patients were obese, it being among the three most common comorbidities of the infected people. 7 This divergency of data among the countries can be justified by the demographic characteristics and prevalence of comorbidities of each population. 8 The Center for Disease Control and Prevention (CDC) considers that people with severe obesity (Body Mass Index (BMI) ≥40 Kg/m²), can present greater risks for the worsening of COVID- 19. 9 Some common connections between SARS-CoV-2 and obesity are respiratory problems. It is well-known that there is a positive correlation among asthma, acute lung injury, obstructive sleep apnea syndrome, acute respiratory distress syndrome, and being overweight. 10 Obesity is associated with a decrease in functional capacity, as well as with a compliance of the respiratory system and the expiratory reserve volume. 11 In France, data from patients that made use of invasive mechanical ventilation have shown that individuals with severe obesity (BMI ≥ 35Kg/m²) presented impaired respiratory patterns in relation to the patients with BMI ≤ 25Kg/m². 12 In this scenerio, obesity represents an independent risk factor for the respiratory hypoventilation syndrome, a potential aggravating factor for complications related to respiratory insufficiency in patients who are admitted to intensive care units. 13 Beyond respiratory complications, another liaison with COVID-19 is inflammation. Obesity causes an increase of secretion of pro-inflammatory cytokines in the adipose tissue, which can worsen if infected by COVID-19. 10,11,14 High serum levels of interleukin-6 (IL-6) have been reported in patients who passed away due to COVID-19. 6 In addition to IL-6, the receptors of interleukin-2 and the tumor necrosis factor-alpha can also take part in endothelial dysfunction. 15 Another important point to be highlighted is the relationship between obesity with cardiovascular diseases/events, such as hypertension, stokes, heart failure, and coronary artery disease, as well as diabetes. However, what has most called attention in this scenario is thrombosis, since obesity can increase the risk of developing this type of blood clot, and, together with COVID-19, it can further aggravate the situation through intravascular coagulation and an increase in the rates of venous thromboembolism. 10 Moreover, a high incidence of cardiovascular symptoms can be observed due to the systemic inflammatory response and the changes caused by the immune system during the course of COVID-19. 16 Thus, the reduction of body weight, despite not reducing the risk of infection, seems to be an important preventive and protective measure against serious cases of SARS-CoV-2, as it favors a decrease in inflammatory processes caused by obesity. Despite the need for more consistent evidence of the protective effect of the regular practice of physical activity and healthy diets in a population contaminated by SARS-CoV-2, 17 these types of behaviors are acknowledged in the literature as effective for the control of obesity in the general population. 18 It has also been speculated that individuals with desirable levels of cardiorespiratory aptitude tend to show a higher protection against the symptoms caused by the SARS-CoV-2 infection, mainly due to an enhanced immunological resistance. 19 Another issue that requires close attention is the possibility of an increase in sedentary behaviors, such as sitting in front of a TV or spending time with electronic gadgets, as these seem to be associated with various chronic non-communicable diseases and cardiovascular mortality. 20 Thus, with the needed recommendations of social distancing, it is feared that the population may reduce the practice of physical activity and increase sedentary behaviors and body weight, even further worsening the scenario of a global endemic of obesity, which could, in the mid-term, at least while there is not a more efficient treatment or the discovery of a definitive vaccine, increase the risk of more complications because of the disease and cause an overload in the health system. Moreover, it is still true that the recommendation of global scientific and health entities is to avoid agglomerations in situations with a high possibility of the transmission of the virus, such as gyms and sports centers, in municipalities and regions that need interventions to flatten the contagion curve.
In this sense, the stimulus for the practice of regular outdoor, or in-home, physical activities for all ages must be better widespread and conveyed, respecting the advice from health authorities and governmental decrees regarding the continuance of social distancing. This is an important message of public health in order to maintain physical and mental health and to cope with this moment of generalized anxiety and the feeling of hopelessness.
There are many alternatives for the practice of physical activities -ones that do not require the use of equipment and that can be done in a family and household environment; however, people need to be encouraged and properly advised. Such activities include aerobic activities, such as dancing, stationary racing, and walking up and down stairs, as well as activities of muscular strength/resistance, which make use of different areas of the body, including yoga, Pilates, and training with body weight (squatting, burpees, sit-ups, ground support, etc.).
Many physical education professionals are already using messages in mobile phones, apps, e-mails, or video calls to prescribe and monitor exercises individually. 21 There are also free initiatives for the guidance of physical activities on the internet, many of which are connected to universities or nongovernmental organizations, according to guidelines set forth by the World Health Organization (WHO), 22 for example, which could be implemented by governments, with mass educational campaigns, freely broadening this message to the entire population.
It is is also important to highlight the need for the maintenance of the practice of physical activity for the elderly, as they tend to have a higher number of chronic, primarily cardiovascular, diseases, and they are more vulnerable to complications caused by SARS-CoV-2. Nevertheless, if symptoms related to COVID-19 appear, the practice of physical activity should be interrupted, regardless of the age group. 21,23 The Pre-Exercise Screening Questionnaire (PESQ), considering the presence of signs and symptoms, was proposed to the current context as an additional tool for initial screening for a safer practice of telepresence exercise. 21 Therefore, it seems that the regular practice of physical activities can aid in the control of obesity, beyond favoring an enhanced immunological response for the current moment of the COVID-19 pandemic. Public health policies should provide assistance not only for individuals, but also for the public in general. They should help people either to continue or become physically active, encouraging people's autonomy and independence, taking into consideration the differences between groups and iniquities in health. These policies are emerging, are of utmost importance and, will become an ever-increasingly important part of the "new normal ".
Finally, this moment of the COVID-19 pandemic may be an opportunity for reflection on our behaviors and individual and collective care related to health. In general, periods of social distancing are not experienced over the long term; however, the decision-making concerning our choices can and should be undertaken throughout our entire life.

Author contributions
Conception and design of the research: Queiroz CO, Conceição AF, Aristides PRS, Alves, LS, Almeida RT. Acquisition of data: Queiroz CO, Conceição AF, Almeida RT. Writing of the manuscript: Queiroz CO, Conceição AF, Almeida RT Critical revision of the manuscript for intellectual content: Queiroz CO, Conceição AF, Aristides PRS, Alves, LS, Almeida RT.

Potential Conflict of Interest
No potential conflict of interest relevant to this article was reported.

Sources of Funding
There were no external funding sources for this study.

Study Association
This study is not associated with any thesis or dissertation work.

Ethics approval and consent to participate
This article does not contain any studies with human participants or animals performed by any of the authors.