We know that obese people have poorer COVID outcomes. It seems like a simple connection with weight. But actually weight and fat are not as tightly related as you might think.
The problem with BMI
The body mass index (BMI) is a practical measure that uses your height and weight to work out if your weight is healthy. But BMI cannot tell the difference between excess fat, muscle or bone, so needs to be interpreted with caution. For example, you might be a healthy weight according to your height, but you can still carry too much visceral fat (more on this below).
BMI may not be helpful if you are:
- Muscular, as BMI may not show accurate fat levels.
- Over 65, due to other health conditions, and possible protective effect of having a slightly higher BMI when older.
- Pregnant.
In fact, your waist measurement is a more accurate indicator or predictor of potential health problems. For example, a 2024 study found that belly fat, indicated by waist measurements, were a better indicator of colorectal cancer risk than BMI, further highlighting the importance of understanding your body fat an where you store it.
So let’s help you better understand and measure body fat.
You must speak to your GP about any unintentional increase or decrease in your weight. This may be a sign of significant illness.
Body fat: The good and the bad
Having fat in our body isn’t all bad – in fact we can’t do without it! Fat surrounds and cushions vital organs like the kidneys and insulates us against the cold. Fat is also our fuel tank, a calorie reserve to protect against starvation.
But having too much fat especially in the wrong places isn’t good. The fat you can see, that sits under the skin, often in rolls, is called subcutaneous fat. The fat you can’t see and that gathers around your organs is called visceral fat. Fat accumulated in the lower body (if you’re pear shaped) is generally subcutaneous, while fat in the abdominal area (if you’re an apple shape) is largely visceral.
Visceral fat is essentially fat that’s stored deeper than subcutaneous belly fat (that’s immediately beneath the skin). It wraps around your major organs including the liver, pancreas and kidneys and contributes to a range of dangerous health conditions such as heart disease, dementia and cancer. Too much visceral fat in your system can make it difficult for you to produce insulin and can increase the risk of developing type 2 diabetes.
How to measure fat
The amount of fat you need to be healthy varies depending on age, sex and ethnicity.
BMI and ethnicity
The National Institute for Clinical Excellence (NICE) generate national guidelines for the UK medical community. NICE 2022 guidelines for categorising BMI now recognise the difference between ethnicities and that certain ethnicities have variations in body composition (i.e. the percentage and distribution of the fat, bone, and muscle in your body), and may carry greater risk of potential health problems at lower BMIs than the usual cut offs.
For people with a with a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background the cut offs are:
| Healthy weight | BMI 18.5 kg/m2 to 22.9 kg/m2 |
| Overweight | BMI 23 kg/m2 to 27.4 kg/m2 |
| Obesity | BMI 27.5 kg/m2 to 37.4 kg/m2 |
| Severely obese | BMI 37.5 kg/m2 or above |
For people whose family background isn’t listed above:
| Healthy weight | BMI 18.5 kg/m2 to 24.9 kg/m2 |
| Overweight | BMI 25 kg/m2 to 29.9 kg/m2 |
| Obesity | BMI 30 kg/m2 to 39.9 kg/m2 |
| Severely obese | BMI 40 kg/m2 or above |
Waist-to-height ratio
According to NICE guidelines, waist-to-height ratio, alongside BMI, is now considered a helpful measurement to predict or indicate potential health issues.
Measure:
To find out yours, simply:
- Grab a tape measure!
- Locate the bottom of your ribs and the top of your hips.
- Wrap the tape measure around your waist midway between these points (this will be just above your belly button)
- Breathe out naturally before taking the measurement, then check the number on the tape measure for your waist circumference.
Calculate:
Be sure to measure your waist circumference and height in the same units. Divide your waist measurement by your height measurement. For instance:
35 inches divided by 64 inches = waist-to-height ratio of 0.55.
Results:
The table below shows what NICE regards as a healthy waist-to-height ratio:
| Healthy levels of fat around the waist | Waist-to-height ratio 0.4 to 0.49, indicating no increased health risks |
| Increased fat around the waist | Waist-to-height ratio 0.5 to 0.59, indicating increased health risks. |
| High levels of fat around the waist | Waist-to-height ratio 0.6 or more, indicating further increased health risks. |
These classifications can be used for adults with a BMI under 35 kg/m2 of both sexes and all ethnicities, including adults with high muscle mass.
NICE encourages adults with a BMI under 35 kg/m2 to keep their waist measurement to less than half their height, to reduce their risk of potential type 2 diabetes, hypertension (high blood pressure) or cardiovascular (heart) disease. So, aim for a waist-to-height ratio of under 0.5.
The NICE advice in the above paragraph isn’t suitable for those with a BMI over 35 Kg/m2 or for pregnant women.
Waist hip ratio
In the Evergreen Life app, we currently ask waist to hip ratio. We’ll soon be swapping this to waist to height ratio to align with NICE guidelines, however, it is still a better indicator than BMI alone or predicting body fat and health risks.
If you enter your waist and hip measurements in the app, it will calculate it for you, or you can simply divide your waist measurement by your hip measurement.
The WHO suggests a healthy WHR is:
- 0.9 or less in men
- 0.85 or less for women
If you have a higher waist hip ratio than this, it’s likely you are storing fat around your middle which could be an indication of higher levels of visceral body fat. That’s the bad stuff.
Look out for your notification to take the BMI and Body Fat Check in the Evergreen Life app to help you maintain or work towards a healthy measurement.
If you don’t have the app, you can download it here. Calculating your waist hip ratio is one of many helpful insights you’ll get if you sign up!
Body fat percentage
To take a truly accurate measurement of your body fat, you’d need a costly scan. You might also consider buying bio-impedance scales that send electrical pulses through your body to “read” how much body fat you have.
If you have time, a few more measurements can give you an estimation of your body fat percentage. The US Navy has developed a standardised body fat calculator which uses age, sex, height, waist and neck measurements. There are a number of these calculators online like this one. This will give you an estimated body fat percentage and give you an idea of clinically-accepted ranges. However, unlike BMI, body fat is an emerging field and there is no agreement on firm boundaries. Remember to record these measurements in the app if you have it!
5 ways to reduce visceral fat
If you find that your body fat is higher than it should be, it might be worth considering these tips for improved health:
1. Give fast food the boot
Refined carbohydrates and sugars contribute heavily to our storage of fat. Firstly, try to cut down on free sugars; that’s found in cakes, sweets, biscuits, chocolate, soft drinks, breakfast cereal and yoghurts etc. Free sugars are also found naturally in honey, unsweetened fruit juice, vegetable juices and smoothies. Try to stick to less than 30g of free sugars per day. It’s worth remembering this is a maximum and not a recommended amount; ideally we wouldn’t be having any but if you’d like a sweet treat, try to let it be just that – a treat.
2. Make good food swaps
Beat hunger and reduce insulin spikes with healthy protein choices. Avoid greasy hamburgers, bacon and processed sausages in favour of fish, lean meats such as turkey or chicken, beans and free-range eggs. Eating healthy fats like extra virgin olive oil, avocados and walnuts, or fermented foods like kimchi, live yoghurt and miso can benefit your insulin balance, gut bacteria, hormones, and weight management. Our article on what’s in healthy diet has some good tips.
3. Lose the booze
Alcohol makes you gain weight around your mid-section, without you realising. It’s so easy to guzzle down hundreds, even thousands, of liquid calories. Extra alcohol units also place strain on the liver, which is already working over time to break down the toxic visceral fat acids, if you carry excess visceral fat. Give your liver a break – alternate beers with water. This article on managing your alcohol intake might help.
4. Smoking – be a quitter
Cigarettes take a toll on almost your entire body. Like visceral fat, smoking increases your risk of cardiovascular disease. Take a step towards quitting today by cutting down the number of cigarettes per week. These 10 tips on the NHS website may also help you quit.
5. Move it
Visceral fat loss comes with combining healthy food and a good fitness routine. Research found high-intensity interval training (also known as HIIT) to be the best method for losing visceral fat. It also helps increase your insulin sensitivity. Essentially HIIT involves short bursts of intense exercise alternated with low-intensity recovery periods. Our article on 5 ways to improve your fitness might help.
Keep track and take action.
It’s a good idea to keep track of your waist alongside your BMI so you really understand where you may have problems, or not! Try to update your measurements in the records section of the app every 3 months. The key is to use same method for taking your measurements each time so you can track your progress.
If you want more help to lose weight or body fat, there are links to Evergreen articles below about diet and fitness, including an interesting one about the role of blood sugar, that you might find helpful.
Evergreen Life | Understanding your BMI: Blood sugar levels and how to regulate them
Evergreen Life | What’s in a healthy diet
Evergreen Life | 7 tips for weight loss
Evergreen Life | 5 key areas to improve your fitness
Want to check your health and overall wellbeing? Download the Evergreen Life app below and take your available questionnaires. Look out for more as they’re released including the BMI and Body Fat Check.
Reviewed by:
Dr James Harmsworth King MBBS MPhil PhD Biotechnology & Medical Expert
Is BMI an accurate way to measure body fat?
Abdominal fat and what to do about it
Waist circumference as a vital sign: Consensus Statement on Visceral Obesity
Why is my waist size important?
The effect of HIIT training on Visceral fat
Recommendations | Obesity: identification, assessment and management | Guidance | NICE
