Healthy weight: what it means and how to reach it

Why does a healthy weight matter?

Carrying too much weight, especially around your middle, raises your risk of a number of health problems. The NHS lists type 2 diabetes, heart disease, stroke, high blood pressure, some cancers, including breast, womb and bowel cancer, osteoarthritis and fatty liver disease among them.

Weight is affected by many things, including your genes, age, hormones, health conditions, medicines, sleep and stress, as well as what you eat and how active you are. That is why it is not simply a matter of willpower, and why support can make a real difference.

How do you know if your weight is healthy?

Body mass index, or BMI, is the most common starting point. It compares your weight with your height, and you can check yours with the NHS BMI calculator. The NHS explains that, for most adults, a BMI of 25 to 29.9 is classed as overweight and 30 or more as obese.

The thresholds are lower for some groups, because people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African Caribbean backgrounds have a higher chance of health problems at a lower BMI. For these groups, the NHS says a BMI of 23 to 27.4 is classed as overweight, and 27.5 or more as obese.

BMI has limits. It cannot tell the difference between muscle and fat, so a very muscular person may have a high BMI without carrying excess fat.

Why does your waist size matter?

Fat stored around your middle is linked to a higher risk of conditions such as type 2 diabetes and heart disease, even if your BMI is in the healthy range. The NHS advises trying to keep your waist size to less than half your height. The NHS has a short video on its obesity page showing how to measure your waist and compare it with your height.

How can you reach a healthy weight?

You do not need to make huge changes. The NHS says losing just 5 to 10% of your body weight can improve your health. For someone weighing 90kg, that is 4.5 to 9kg.

Slow, steady changes you can keep up work best. Eating more fruit, vegetables and fibre-rich foods, which help you feel full, cutting down on sugary drinks, snacks and large portions, and being more active all help. Crash diets may work in the short term, but the weight often comes back.

The free NHS Weight Loss Plan app can help you set a goal and build healthier habits over 12 weeks. If you have a health condition affected by your weight, such as high blood pressure or type 2 diabetes, your GP may be able to refer you to specialist support.

What if you are underweight?

Being underweight can also affect your health, and it can sometimes be a sign of an underlying problem. If your BMI is below the healthy range, or you are losing weight without trying, speak to your GP before trying to change your weight.

How can families help children stay a healthy weight?

Children grow at different rates, so their BMI is worked out differently from adults, taking their age and sex into account. You can check a child's BMI with the NHS calculator for children and teenagers.

Children's weight is a growing concern. The National Child Measurement Programme found that in the 2024 to 2025 school year, 22.2% of Year 6 children in England were living with obesity.

Healthy habits are easiest to build as a family. The NHS Healthier Families website has ideas for meals, snacks and activities, and makes the point that small steps soon add up. Focusing on health and fun rather than weight, eating together, and making activity part of everyday life all help. If you are worried about your child's weight, speak to your GP or school nurse.