What do we know about obesity and COVID-19?

March 9, 2021

Dr Deborah Lee, Dr Fox Online Pharmacy, highlights the possible reasons why being obese affects the risk of COVID-19 infection

Do you have a BMI of >25? Or perhaps >30? If so, you are in good company.

3% of the UK population are overweight (BMI 25-29.9) or obese (BMI 35-39.9) (www.gov.uk)
3% are severely obese (BMI >40). Severe obesity has increased significantly in recent decades, and scientists predict numbers are set to double by the year 2035.

Obesity is a killer, especially in the face of infection with COVID-19. As BMI rises, so does your risk of severe COVID infection, and death.

There’s never been a better time to lose weight, once and for all. Being overweight has many physical and psychological consequences. Are you in denial about your weight? When did you last work out your BMI?

Read on and find out the reason why losing weight right now is so important.

Obesity and COVID-19 infection – the facts

In July 2020, Public Health England produced a detailed report on all the relevant, up-to-date information about obesity and COVID-19. Much of the information here derives from this report.

Obesity, even without COVID infection, has serious effects on your health –

Obesity – reduces life expectancy in men by 4.2 years, and in women by 3.5 years.
Severe (morbid) obesity – reduces life expectancy in men by 9.2 years, and in women by 7.7 years.

Obesity is a disease, not just a lifestyle factor

Obesity has now been classified by the American Medical Association as a disease, not just a lifestyle factor.

Being obese is not a question of being lazy and greedy. It’s a real medical condition that deserves just as much attention, understanding, and support as any other medical condition.

Why does obesity reduce life expectancy?

Obesity increases the risk of high blood pressure, heart attack, stroke, heart failure, type-2 diabetes, non-alcoholic liver disease, and various types of cancer.

What’s the link between obesity and COVID-19?

These medical conditions occur far more often in people hospitalized with severe COVID infection, leading experts to believe that obesity is a common underlying factor.

How much does obesity increase your risk of COVID-19 infection?

Let’s consider the following statements –

Obesity increases your risk of COVID-19 infection

In a recent study, (Yates, 2020) using data from the UK Biobank, the authors demonstrated the risk of COVID-19 infection increased as both BMI and waist circumference increased. Being overweight, obese, or severely obese, increased the risk of COVID infection by 31%, 55%, and 57%, respectively.

Obesity increases the risk of needing to be hospitalized due to COVID-19

Hamer 2020 also studied data from 387,019 members of the UK biobank and calculated that being overweight (BMI/25), or obese (BMI>30), increased the risk of being admitted to hospital from COVID infection by 32%, and 97%, respectively.

A recent (May 2020) New York study in the British Medical Journal (BMJ) reported that people with obesity (BMI of >30), and severe obesity (BMI >40), were 4, and 6 times respectively, more likely to be admitted to hospital with COVID infection, than those with a BMI <30.

Obesity is directly linked to worse COVID outcomes

A systematic review and meta-analysis (Yang 2020), published in the Journal of Virology, concluded obesity increased the risk of severe COVID infection by a factor of 2.5, and the risk of a poor outcome by a factor of 2.3.

A meta-analysis published in the journal Obesity, Research and Clinical Practice (Hussain 2020), including results from 14 studies of 403,535 patients, concluded that compared to those with a normal BMI, obesity (BMI >25) doubled the risk of being critically ill, almost quadrupled the risk of death, and the risk of needing respiratory support was increased almost 7 times.

Obesity increases the risk of death from COVID infection

Many studies have reported an increased risk of death from COVID with increasing BMI.

For example, in May 2020 the British Medical Journal published a study of 20,133 patients admitted to 208 UK hospitals with COVID-19. Obesity (BMI>30) increased the risk of death by 33%.

Why does obesity increase the risk of Covid-19?

There are many possible reasons why obesity increases your risk from COVID-19. These reasons were described in the journal Molecular Medicine Reports Petrakis, (May 2020).

Here is an explanation of their key findings – it’s a bit technical I’m afraid, but I’ve simplified it the best I can –

Obesity lowers immunity to other respiratory infections

Obesity is known to impair immunity to other respiratory viruses, such as influenza, and reduces the response to the influenza vaccine (Green, 2017).

High blood glucose, and diabetes, both associated with obesity, have also been linked to increased morbidity and mortality from infections with other coronaviruses, for example, those causing the Severe Acute Respiratory Syndrome (SARS) outbreak in 2003, and the Middle Eastern Respiratory Syndrome (MERS) outbreak in 2012.

Obesity has a negative effect on lung function

Being obese results in impaired lung function. There is increased fat deposition in the chest wall, the chest cavity (thorax), and the abdominal cavity (under the diaphragm) meaning that that in those who are obese, the chest is relatively compressed. Even without COVID-19 infection, obese individuals are working harder to maintain normal breathing.

Obesity results in chronic inflammation and increases the risk of Acute Respiratory Distress Syndrome (ARDS)

COVID-19 enters the body through ACE2 receptors, found predominantly in the lung, and kidney, but also in the heart, and blood vessel walls. Activation of these receptors is integral in the control of blood pressure, as well as many other functions including the immune response, and regulating the process of inflammation.

Obesity is associated with chronic inflammation. Indeed, those with higher BMI levels often have metabolic syndrome – a medical condition in which various metabolic processes are deranged, and which further increase the risk of atherosclerosis, and systemic (whole-body) inflammation. When you are obese, if you become infected with COVID-19, at the point of infection, your immune system is already over-activated.

In an obese person, when COVID-19 blocks your ACE2 receptors, your ACE1 receptors become relatively over-stimulated. This results in an outpouring of inflammatory cytokines (cell-signalling molecules) as the immune system goes into overdrive – known as a cytokine storm.

In a cytokine storm, your lungs are overwhelmed with these cytokines, whose job it is to kill infected cells. The huge number of cytokines is so great, that instead of helping defend your body from infection, they destroy lung tissue. The air sacs in the lungs become filled with fluid, fluid, meaning oxygen cannot pass freely not the bloodstream and carbon dioxide cannot easily be excreted. This condition is called Acute Respiratory Distress Syndrome (ARDS).

This means people who are overweight or obese, have a higher risk of severe lung disease, requiring hospital admission, critical care, and mechanical ventilation. The CDC reports that the risk of death is ten times higher from COVID-19 infection, in people with metabolic syndrome and type-2 diabetes.

COVID-19 may block pancreatic islet cell receptors

ACE2 receptors are also found in the islet cells of the pancreas. It has been suggested that COVID-19 may enter these islet cells, temporarily preventing the production of insulin, raised blood sugar, and causing type-2 diabetes. This may explain why people who are already diabetic, are especially vulnerable to COVID-19 infection.

Obesity is a cause of insulin resistance

With increasing obesity, your body becomes less sensitive to the hormone insulin. This is known as insulin resistance. In fact, as glucose levels rise, more and more insulin is produced, but your cells have difficulty recognizing and responding. Eventually, blood glucose levels can no longer be kept under control – this is prediabetes. In due course, if no steps are taken, full-blown diabetes sets in.

Insulin resistance is harmful as it underpins the development of many different medical conditions.

Why does obesity cause insulin resistance?

Firstly, because visceral fat produces cytokines that directly impair the sensitivity of cells to insulin – the more visceral fat, the higher the number of cytokines.
Secondly, the quantity of visceral fat may be a marker of lipotoxicity, which is a direct cause of insulin resistance in the liver and muscle. On a high-fat diet, excess fat stored in fat cells is a cause of insulin resistance.
Thirdly, some studies have shown that adipocytes (fat cells) have a relatively poor oxygen supply and are less able to grow and develop a substantive, capillary network. This may be a cause of insulin resistance.

The exact reasons insulin resistance worsens the prognosis of COVID-19 infection are still not fully understood. However, activation of the ACE2 receptor is known to enhance insulin signalling and reduce insulin resistance. COVID-19 attaches to the same receptors and may blunt this activity. More research is needed.

Obesity results in raised leptin levels

Adipocytes (fat cells) produce a hormone called leptin. This is a hormone that regulates appetite. High leptin levels make you feel full and help to stop you from eating. It also increases your energy expenditure.

Strangely, obese people tend to have higher leptin levels, probably due to leptin resistance. As a result, even though leptin levels are high, they still have a large appetite. High leptin levels accelerate atherosclerosis, causing damage to endothelial cells and lowering HDL (‘good’) cholesterol.

Leptin is a cell-signalling molecule, which itself triggers the production of inflammatory cytokines (interleukins 2 and 6, and tumour necrosis factor) and sets off the inflammation cascade.

The good news is that leptin levels fall with weight reduction.

Those who are obese often have an unhealthy diet, which in turn, damages the gut microbiome

Many studies have shown that people who are obese tend to have an unhealthy diet – eating large amounts of fast food and processed food. These are often high-fat, high-protein, high-salt, low- fibre, low in complex carbohydrates (carbs which release energy slowly), and low in vitamin D. These foods may also be contaminated with pesticides.

This diet causes changes to the gut microbiome, increasing the ‘leakiness’ of the gut wall. This means the junctions between intestinal cells are weakened, such that bacteria, viruses, and toxins can pass from the gut contents into the bloodstream. These effects then further exacerbate systemic inflammation.

There is also a link between the unhealthy Western diet and autoimmune diseases. High-salt increases the risk of high blood pressure, cardiovascular disease, and stroke.

Large amounts of visceral fat produce large numbers of inflammatory cytokines

Fat is not an inactive tissue. In fact, visceral fat produces large numbers of cytokines, such as Interleukin 6 (IL-6), and tumour necrosis factor-α (TNF-α). IL-6 has several important roles, for example in the regulation of B and T lymphocytes. TNF- α regulates many aspects of immune function, for example, to cause cell death and destruction.

In addition, eating a high-fat diet has been shown to increase the production of these cytokines.

Lipotoxicity has dangerous consequences

Too much dietary fat can literally poison your organs. Lipotoxicity occurs when there is so much dietary fat, that adipocytes (fat cells) cannot store any more, and the excess fat spills over into the bloodstream. Free fatty acids are then stored in other tissues such as the liver, heart, and kidneys. These fats are toxic and cause organ damage, for example, non-alcoholic liver disease, heart failure, and kidney failure.

Lipotoxicity is also associated with insulin and leptin resistance.

Oxidative stress, associated with obesity, damages red cell membranes

Oxidative stress is another type of metabolic derangement, in which electrically charged particles called ‘reactive oxygen species’ (ROS), cause tissue destruction.

Obesity increases oxidative stress. As a result, there is an increased breakdown of lipids in the walls of red blood cells, meaning these red cells, carrying vital haemoglobin, are less able to squeeze through microcapillaries, and release oxygen as they should.

Increased oxidative stress seems also to increase damage to the air sacs in the lungs, the alveoli, and to stimulates coagulation, leading to an increase in microvascular thrombosis.

Obesity increases your susceptibility to infection

Obesity seems to increase general susceptibility to infection. Some have suggested that COVID-19 may even use excess adipose tissue as a reservoir where it can replicate, and to facilitate viral shedding, and enhance transmission of infection.

There is some evidence that people living with obesity have worse COVID symptoms than those with a normal BMI.

Obesity is linked to heart disease

In obesity, there is increased fat deposition in the heart muscle, but the effects on the heart are further compounded as obesity is also associated with high blood pressure, metabolic syndrome, and diabetes.

In the heart, obesity results in obesity-related cardiomyopathy, with enlargement and fat deposition in cardiac muscle cells. Obesity is liked to sleep apnoea, meaning the heart is relatively under-perfused with oxygen during sleep.

Summary

If you are obese, there are numerous biochemical and metabolic reasons why COVID-19 infection is more likely to be severe and have a poor outcome. This is due to a combination of factors.

You are likely to have higher levels of chronic systemic inflammation, along with insulin resistance, and oxidative stress.
When the COVID-19 virus particles attach to your ACE2 receptors, there is an increased risk of an overwhelming immune response, leading to a cytokine storm and ARDS.
A high-fat results in an altered microbiome, and an increase in dangerous lipotoxicity, affecting your liver, your heart, and other organs of the body.

Time to take action – Time to lose weight right now

Are you convinced? It’s all pretty scary. But here’s the good news – losing weight will reverse many of these parameters and help keep you well. What’s stopping you? – The time is now.

Lose 5% of body weight

You don’t need to have unrealistic targets. Just losing 5% of your body weight will reduce insulin resistance and relieve oxidative stress. Even a mere 5% weight loss has major health benefits.

For example, if you weigh 100kg, 5% is 5kg (11 lb).

If you lose 2lb a week you can lose this in just 5-6 weeks.

And there are so many benefits of losing weight – quite apart from improving your chances from COVID.

Final thoughts

Obesity and COVID-19 are a double pandemic. It’s a frightening reality.

However, now you know the facts, you can make up your mind right now, to change things for the better. Don’t let the virus win!

Why not see your GP and discuss ways you can lose weight, and what support is available? There are many different weight-losing diets, but if you have a lot of weight to lose, you can take weight loss medication, or be referred for bariatric surgery. Why not find out what you can do and get started right away?

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