Obesity and overweight have been called out as risk factors for COVID-19 since the early days of the pandemic, and research continues to suggest that carrying excess weight could raise your risk of COVID complications and death. Even mild obesity may raise the risk of COVID-19 severity, calling into question current United Kingdom guidelines that only classify severe obesity as a risk factor.
The new finding was revealed by researchers from the Alma Mater Studiorum University of Bologna in Italy, who analyzed 482 COVID-19 patients hospitalized between March 1 and April 20, 2020.1 “Obesity is a strong, independent risk factor for respiratory failure, admission to the ICU and death among COVID-19 patients,” they wrote, and the extent of risk was tied to a person’s level of obesity.
‘Mild’ Obesity Increases Risk of Severe COVID-19 Illness
The researchers used body mass index (BMI) to define obesity in the study, and although BMI can be misleading in determining whether or not you’re at a healthy body weight, in part because it does not take muscle mass into account. It’s the most commonly used measurement for defining obesity.
If your BMI is between 25 and 29.9, you are considered overweight and anything over 30 is considered obese. However, obesity is often divided into categories, with class 1 defined as a BMI of 30 to < 35, class 2 as a BMI of 35 to < 40 and class 3 defined as a BMI of 40 or higher, and considered "extreme" or "severe" obesity.2
The U.K.’s National Health Service states that you may be at moderate risk from coronavirus if you are “very obese” with a BMI of 40 or above,3 but the featured study found increased risks started at a BMI of 30, or “mild” obesity.
“Health care practitioners should be aware that people with any grade of obesity, not just the severely obese, are a population at risk,” lead study author Dr. Matteo Rottoli said in a news release. “Extra caution should be used for hospitalized COVID-19 patients with obesity, as they are likely to experience a quick deterioration towards respiratory failure, and to require intensive care admission.”4
Specifically, patients with mild obesity had a 2.5 times greater risk of respiratory failure and a five times greater risk of being admitted to an ICU compared to nonobese patients. Those with a BMI of 35 and over were also 12 times more likely to die from COVID-19.5
“Whereas a BMI ≥ 30 kg/m2 identifies a population of patients at high risk for severe illness, a BMI ≥ 35 kg/m2 dramatically increases the risk of death,” the researchers explained.6
A July 2020 report7 by Public Health England also describes the results of two systematic reviews,8 one of which showed that excess weight worsened COVID-19 severity, and the other that obese patients were more likely to die from the disease compared to non-obese patients.
Compared to healthy weight patients, patients with a BMI above 25 kg/m2 were 3.68 times more likely to die, 6.98 times more likely to need respiratory support and 2.03 times more likely to suffer critical illness. The report also highlights data showing the risk of hospitalization, intensive care treatment and death progressively increases as your BMI goes up.
Obesity, Metabolic Syndrome Linked to Severe COVID-19, Flu
Additional research has also tied obesity and metabolic syndrome — a cluster of conditions including excess abdominal fat, high blood pressure, insulin resistance and lipid abnormalities that increase the risk of heart disease, stroke and Type 2 diabetes — with more severe viral infections.9
Obesity is known to double the risk of influenza,10 for instance, and increases the duration of stay in the ICU along with the need for invasive mechanical ventilation during such infections.11 And obesity is one of the primary causes of metabolic syndrome. According to an article published in the Journal of Virology:12
“Viruses can metabolically engineer host cells by manipulating gene expression and lipid metabolism to enhance viral replication and progeny release while enabling the virus to evade host immune responses. Because metabolic disorders impair immune responses at homeostasis, viral infection further compromises these responses and potentiates metabolic disease severity.”
As for how obesity raises risks during viral infections, the chronic, low-grade inflammation it causes is a likely factor. In fact, inflammation triggered by obesity may be responsible for a threefold greater risk of pulmonary embolism (blood clots in the lungs) in COVID-19 patients who are obese,13,14 according to separate research.
The Journal of Virology researchers also suggested that dysregulated lipid synthesis triggered by obesity may aggravate inflammation in the lungs, contributing to increased disease severity during respiratory viral infections.15 As for SARS-CoV-2, the virus that causes COVID-19, they cited one study that found nearly 50% of hospitalized COVID-19 patients were obese and admitted into ICU in need of mechanical ventilation.
“This is not surprising because excess body weight and fat deposition apply pressure to the diaphragm, which further increases the difficulty of breathing during a viral infection,” they wrote.16 Additional mechanisms are also suggested for how obesity increases COVID-19 severity, including:17
- Increasing leptin resistance and lipotoxicity, as the accumulation of lipids may be exploited by viruses to enhance viral entry and replication
- A combined effect of chronic systemic inflammation and the induction of a cytokine storm
Boris Johnson Takes on Obesity to Target COVID-19
After spending time in the hospital due to COVID-19, prime minister Boris Johnson announced a new strategy to target obesity in the fight against coronavirus.18 Johnson believes that his weight made his COVID-19 infection more severe, and reportedly plans to implement bans on TV junk food advertising before 9 p.m., as well as targeting junk food ads online and in stores.19
Indeed, processed foods, junk foods and soft drinks are key culprits in the rise of obesity and chronic diseases that have a key role to play in COVID-19 deaths. London-based cardiologist Dr. Aseem Malhotra is among those warning that poor diet can increase your risk of dying from COVID-19.
He tweeted, “The government and Public Health England are ignorant and grossly negligent for not telling the public they need to change their diet now.”20
He told BBC that ultraprocessed foods make up more than half of the calories consumed by the British, and if you suffer from obesity, Type 2 diabetes and high blood pressure — all of which are linked to poor diet — your risk of mortality from COVID-19 increases 10fold. The Journal of Virology researchers agreed, writing:21
“Over the years, humans have adopted sedentary lifestyles and dietary patterns have shifted to excessive food consumption and poor nutrition. Overnutrition has led to the constellation of metabolic abnormalities that not only contributes to metabolic reprogramming but also limits host innate and adaptive immunity.
Impaired immune responses and chronic inflammation in metabolically diseased microenvironments provide the ideal conditions for viral exploitation of host cells and enhanced viral pathogenesis.”
Researchers Say Food Industry Shares Blame for COVID-19
In an editorial published in the BMJ,22 three researchers cited the role of the food industry in driving up rates of obesity and ultimately causing more COVID-19 deaths:23
“It is now clear that the food industry shares the blame not only for the obesity pandemic but also for the severity of covid-19 disease and its devastating consequences.
During the COVID-19 pandemic an increase in food poverty, disruptions to supply chains, and panic buying may have limited access to fresh foods, thus tilting the balance towards a greater consumption of highly processed foods and those with long shelf lives that are usually high in salt, sugar, and saturated fat.
Moreover, since the start of the COVID–19 pandemic the food industry has launched campaigns and corporate social responsibility initiatives, often with thinly veiled tactics using the outbreak as a marketing opportunity (for example, by offering half a million “smiles” in the form of doughnuts to NHS staff).”
They not only called on the food industry to stop promoting unhealthy food and drinks immediately, but also called on governments to force reformulation of junk foods to better support health.
With research showing that being obese doubles the risk of being hospitalized for COVID-19,24,25 researchers noted, “These findings suggest that modification of lifestyle may help to reduce the risk of COVID-19 and could be a useful adjunct to other interventions, such as social distancing and shielding of high risk.”26
Johns Hopkins University researchers suggested obesity could also shift the burden of COVID-19 onto younger patients, finding in a dataset of 265 COVID-19 patients that younger individuals admitted to the hospital were more likely to be obese.27
Losing Weight May Lower COVID-19 Risk
If you’re obese, focusing on healthy weight loss may help to ward off viral illnesses, including COVID-19. “In the mid- and long-term, weight loss is the definitive answer to reduce the risks in people with obesity,” Rottoli said.28 Losing weight will also help you avoid obesity-related health problems like diabetes, high blood pressure and heart disease.
According to a study by The Istituto Superiore di Sanità, Italy’s national health authority,29 more than 99% of fatalities from COVID-19 occurred among people who had underlying medical conditions. Among the fatalities, 76.1% had high blood pressure, 35.5% had diabetes and 33% had heart disease.30
One of the most powerful strategies to optimize your weight is simply restrict your eating window to 6 to 8 hours with not eating at least three hours before bedtime. This is known as time-restricted eating and a powerful intervention to reduce insulin resistance and restore metabolic flexibility.
Nutrition-wise, I recommend adopting a cyclical ketogenic diet, which involves radically limiting carbs (replacing them with healthy fats and moderate amounts of protein) until you’re close to or at your ideal weight, ultimately allowing your body to burn fat — not carbohydrates — as its primary fuel.
Once you have regained your ideal body weight than you can cycle carbs back in a few times a week.
It will also be wise to avoid all processed foods and also limit added sugars to a maximum of 25 grams per day (15 grams a day if you’re insulin resistant or diabetic). KetoFasting, the program I developed and detail in my book, “KetoFast: A Step-By-Step Guide to Timing Your Ketogenic Meals,” combines a cyclical ketogenic diet and intermittent fasting with cyclical partial fasting to optimize weight, health and longevity.
In addition, get regular exercise each week and increase physical movement throughout your waking hours, with the goal of sitting down less than three hours a day, while also getting sufficient sleep and tending to your emotional health.
Chronic stress, for instance, may increase your risk for visceral fat gain over time,31 which means addressing your stress levels is imperative for maintaining your ideal weight. Taking steps to lead a healthy lifestyle overall will have a snowball effect, helping you to reach a healthy weight while also bolstering your resilience against infection and disease.