Obesity

In the UK, 1 in 4 adults are currently classified as obese, and obesity contributes to 11% of cardiovascular deaths. In this article, you’ll learn about obesity and what you can do to lower your risk.

The World Health Organization defines obesity as an excessive or abnormal accumulation of body fat, which can present a risk to health.¹ Whilst the exact mechanisms linking obesity to cardiovascular disease are still being investigated, it’s thought that excess adipose tissue induces the production of inflammatory molecules which contribute to atherosclerosis and increase the risk of heart attacks and ischaemic strokes.² Excess body mass also means the heart has to work harder, which may contribute towards heart failure. Obese individuals tend to have higher blood pressure, higher cholesterol, and higher triglycerides, all of which are linked to cardiovascular disease.

How do we measure obesity?

Two commonly used tools for measuring obesity are the body mass index (BMI) and waist circumference.

Body mass index (BMI)

Calculation for BMI: BMI = weight (kgs)/height (m)²

Alternatively, you can use the NHS BMI calculator to calculate and interpret your BMI. Although there are different BMI cut-off points in place for different ethnicities, it is generally believed that a BMI of 25+ means that a person is overweight, while a BMI of 30+ indicates that someone is obese:

BMI is a crude measure of obesity (as it does not discriminate between fat and muscle mass), but overall, it correlates well with the risk of cardiovascular disease.³ People with athletic builds should interpret BMI with caution, as they may have a high BMI without having excess body fat. BMI also doesn’t take fat distribution into account, so combining BMI with waist circumference may be a better indication of obesity.

Waist circumference

Where we store body fat affects our risk of cardiovascular diseases. Apple-shaped individuals tend to store their excess fat around their middle, whilst pear-shaped individuals tend to have a smaller waist and larger hips and thighs. A pear shape is believed by many to be cardioprotective or beneficial to heart health. An apple shape is associated with more visceral fat (the fat that surrounds the internal organs of the body), which in turn is linked to an increased risk of cardiovascular disease.

The NHS recommends keeping your waist size to less than half your height. The NHS online calculator explains how to measure your waist correctly, how to calculate your waist-to-height ratio, and how to interpret the results:

What can you do to lower your risk?

Obesity is caused by an energy imbalance that results from a complex web of factors.⁴ Physical inactivity, sedentary behaviour, and poor eating choices are well-established contributors to body shape and size, whilst hormonal imbalances, stress, poor sleep, our genes and even some medications can make some individuals more susceptible to obesity. We’ll learn more about the links between cardiovascular disease and diet and physical activity later in the week.

You can download the Week 4 supplement, which contains additional images and descriptions to help you understand the topics covered in this step.

All statistics from British Heart Foundation unless cited otherwise. British Heart Foundation (2025) Heart & Circulatory Disease Statistics, 2025 Compendium. [Internet]. London: British Heart Foundation; 2025 [cited 2025 Oct 9]. 183p. Available from: https://www.bhf.org.uk/what-we-do/our-research/heart-statistics/heart-statistics-publications/cardiovascular-disease-statistics-2025