Understanding healthy weight beyond BMI

What is BMI and why does it matter?

BMI stands for Body Mass Index. It’s a measurement that’s calculated by dividing your weight in kilograms by your height in metres squared. This calculation gives a score that’s plotted on a range to indicate whether a person is underweight, a healthy weight, overweight, or obese. The NHS uses the following categories to interpret a person’s result. This table is intended for use by adults aged 18 and over. If you have concerns about your weight and one of the following applies to you, speak to your GP for support and advice:

• You’re currently pregnant

• You’re living with a condition that affects your height

• You’re experiencing symptoms of an eating disorder

Using BMI as a measurement tool has several benefits for individuals and healthcare professionals, including:  

• Simple and accessible – you can find free BMI calculators online that offer step by step instructions, with many providing suggested next steps based on your result.  

• Standardisation – BMI is widely used in healthcare settings and provides a standardised range for clinicians to work from when supporting patients. 

• Effective screening tool – BMI can quickly indicate to individuals and healthcare professionals whether their weight may be negatively impacting their health. It can serve as a starting point for further investigation.  

It does also have several limitations, which is why it’s important to consider other factors when determining a healthy weight. These limitations include:

• Varying health risks depending on ethnic background – some people have an increased risk of developing certain health conditions at a lower BMI. If you’re from a South Asian, Chinese, other Asian, Middle Eastern, Black African or African–Caribbean background, the category thresholds are 23-27.4 to indicate overweight and 27.5 or higher to indicate obesity.  

• No distinction of body composition – BMI cannot differentiate between muscle and fat. A person with high muscle mass such as an athlete could have a high BMI signifying overweight or obesity when in fact their body composition features a much lower percentage of fat. BMI also can’t account for loss of bone density, making it less accurate in older people.  

• Other factors aren’t accounted for – such as lifestyle habits, activity levels, diet and genetic factors. These all contribute to a holistic view of our overall health and wellbeing.

How the waist-to-height measurement can give a clearer picture

To address some limitations of the BMI measurement, looking at your waist-to-height ratio alongside BMI can give a broader picture of how body fat distribution may affect your health. It can provide an indication of how much visceral fat (an active type of fat that can influence hormones and protein levels in the body) you have around your tummy. Too much visceral fat can have a negative impact on organs including the heart, liver and pancreas.

Breathing normally, use a soft tape measure to take your waist circumference. You’re aiming for halfway between your lowest rib and the top of your hip. When you have it, divide this by your height using the same unit of measurement (cm or inches).

The NHS describes a typically healthy waist-to-height ratio as between 0.4 to 0.49. A measurement of 0.5 to 0.59 could suggest an increased risk of health complications, while a ratio of 0.6 or over can indicate a significantly higher risk of weight-related health conditions.

Why your weight matters for your health

Maintaining a healthy weight, alongside a balanced diet and regular activity, can support overall physical and mental wellbeing. A healthy weight can also reduce the risk of developing certain health conditions. Obesity is a known risk factor for:  

• Heart disease 

• Type 2 diabetes 

• Stroke 

• Osteoarthritis 

• Fatty liver disease 

• Sleep apnoea 

For some people living with overweight or obesity, losing 5 to 10% of body weight can improve certain health markers, although individual results vary.

How to support sustainable changes

It can be tricky to maintain motivation sometimes, so planning and setting realistic goals can help keep you on track. If you’re trying to lose weight, the NHS recommends gradual weight loss of around 1-2lbs a week.  

Meal planning and batch cooking can help if you’re short on time during the week. There’s plenty of recipe inspiration for breakfasts, lunches and dinners for the whole family on the NHS Healthier Families website. Planning ahead means you can factor in key food groups to each meal, and it can help you consume the recommended 5 a day when it comes to your fruit and veg intake.  

Introducing regular activity to your daily routine can seem daunting if you already have a busy schedule. We’ve outlined simple ways to get active each day with suggestions for incorporating movement into everyday activities. Adult guidance is to aim for around 2.5 hours of moderate intensity exercise, or 75 minutes of vigorous intensity activity each week, as well as including strengthening activities at least 2 days per week.  

Staying hydrated supports general health. Choosing water instead of fizzy or sugary drinks can also help reduce sugar and calorie intake.

When it might be time to get a professional assessment

If you’re finding it hard to lose weight, or you have a weight-related health condition and want extra support from a healthcare professional, consider speaking to your GP or accessing help from a registered clinician. We offer a range of support to help people reach and maintain a healthy weight, from lifestyle guidance in our Health Hub to clinician-led assessments and advice.  

The information in this article is intended for general guidance and should not replace personalised advice from a healthcare professional.