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BMI and the risk of COVID-19

By this point in the COVID-19 pandemic, most people have probably read that certain people are at higher risk from coronavirus. These include the elderly, males and those with diabetes and most recently (and perhaps the most important ‘preventable’ risk factor), having a high BMI (see Coronavirus - healthy diet, healthy outlook and Weight gain in lockdown. How can we stop it? for information on the research).

BMI stands for Body Mass Index. It is a simple calculation of body weight divided by height squared. So, if you weigh 80kg and you are two metres tall, your BMI is 20 (80 ÷ 4 = 20). In other words, it measures how heavy you are relative to your height. You can use our simple BMI checker to find yours. A high BMI means you are heavy for your height and a low one means you are light.

So, you may be asking, ‘what should my BMI be?’ Well, according to convention, ‘normal’ BMI is in the range of 18.5-25. Below 18.5 is underweight, between 25-30 is overweight and over 30 is obese.

Having a BMI below 18.5 or above 25 has been shown to be associated with a greater risk of health problems and having a BMI over 30 is the point at which those health problems become even more common. However, one question I am often asked is ‘can BMI be wrong?’ The answer is ‘yes’ and ‘no’. Let me explain. The basic calculation, if done properly, is going to be correct. So, in that sense, BMI isn’t wrong but if you are asking whether it is valid, in other words, does it consistently predict who is at highest risk of disease, the answer is much more nuanced.

First of all, these BMI ranges are intended to be a ‘rule of thumb’, for the ‘average’, sedentary person and they can be misleading when used with certain people. The best example of BMI being an inappropriate measure is in people who are muscular. If you measure people who do strength or power sports, they may have very little body fat, a small waistline and a large amount of muscle. As muscle weighs much more than fat, their BMI calculation is not measuring their excess fat (which is associated with inactivity, poor diet and disease), but their excess muscle.

For instance, professional bodybuilders in contest condition can weigh over 20 stone and have remarkably low levels of body fat, yet have BMIs in excess of 40 – that’s ‘morbidly obese’! So BMI, on its own, isn’t always the best indicator. For these reasons, most good weight loss coaches, nutritionists and doctors look at BMI as only one indicator of health risk. It’s also the reason why The 1:1 Diet Consultants will also measure areas like waist circumference, giving a much clearer picture of actual body fat. Waist circumference on its own is broadly a good measure of weight-related health risk and it has the added advantage of measuring ‘visceral fat’ – fat located around the midsection and vital organs of the body, which is highly associated with disease.

So, getting back to COVID-19… Armed with a client’s BMI, waist circumference and the training and experience to use these and other tools to implement the best individualised diet strategy, a The 1:1 Diet Consultant can help you both reduce your BMI and take inches off your waist. Importantly, it is not necessary to adopt an extreme diet or to lose large amounts of weight to improve your resilience and health. Studies clearly show that moderate weight loss significantly reduces the risk of various diseases and lowers inflammation. This is important because inflammation has been described as a ‘common feature’ associated with severe COVID-19 disease, and obesity is known to be a state of chronic inflammation. So whether you want to achieve a remarkable weight-loss transformation or just lose a few pounds to improve your health, a Consultant, using our nutritionally-complete meal replacement products and proven Plan, can give you the best odds of success.

Mark Gilbert, BSc, RNutr, CISSN

Nutritionist, The 1:1 Diet by Cambridge Weight Plan