Adult Obesity: Definition, Prevalence and Health Risks

Adult obesity is a specifically defined, widely studied area of UK public health, distinct from childhood obesity, with its own dedicated government resources, including the Better Health campaign and professional guidance such as Adult Obesity: Applying All Our Health. This page covers how adult obesity is defined and calculated, how common it is, the health risks associated with it, and genuine, evidence-based approaches to prevention.

This page also covers the specific, genuine government resources that exist for adult obesity in the UK, since these are real, publicly available tools worth knowing about directly, rather than something you'd only hear about secondhand.

Key things to know

• Adult obesity is generally defined as a BMI of 30 or above, although lower BMI thresholds are used for some ethnic groups because health risks can occur at a lower BMI.
• Around three in ten adults in the UK are currently living with obesity, with figures varying slightly by nation.
• Obesity in adults is associated with an increased risk of several serious long-term health conditions.
• The UK government runs Better Health, a public campaign supporting adults toward a healthier weight, alongside professional clinical guidance for healthcare staff.
• Adult obesity is defined and assessed differently to childhood obesity, which uses age-specific growth charts rather than fixed thresholds.
• Prevention in adults centres on sustainable, family or household-level habits rather than short-term restriction.

What Counts as Adult Obesity?

For most adults, obesity is defined as a BMI of 30 or above. However, BMI is not interpreted in exactly the same way for everyone. UK guidance uses lower thresholds for some ethnic groups because they may develop weight-related health problems at a lower BMI. BMI should also be interpreted with caution in older adults and people with high muscle mass.

How to Calculate Obesity in Adults

Adult BMI is calculated by dividing weight in kilograms by height in metres squared. For most adults, a BMI of 30 or above falls within the obesity range, although lower thresholds are used for some ethnic groups.

How Common Is Adult Obesity in the UK?

Around one in four to one in three adults are living with obesity across the UK, although the latest figures vary between England, Scotland, Wales and Northern Ireland and come from different national surveys.

The Impact of Adult Obesity on Health

Obesity in adults is associated with an increased risk of several serious long-term health conditions, including type 2 diabetes, cardiovascular disease, sleep apnoea, and osteoarthritis, along with an increased likelihood of mental health difficulties. These risks tend to increase with the severity of obesity, and are influenced by additional individual factors, including where fat is stored on the body, not BMI alone. For a fuller look at the health risks specifically, see our full obesity overview.

UK Government Resources for Adult Obesity

The Better Health campaign

Better Health is a UK government public health campaign, delivered through NHS resources, that provides practical support for adults working towards healthier habits and weight management.

The Better Health campaign launched in 2020 and has continued through subsequent campaigns and updates. It is designed to sit alongside, rather than replace, individual clinical support, offering general tools and structure that many people find a genuinely useful starting point.

Adult Obesity: Applying All Our Health

Adult Obesity: Applying All Our Health is a piece of UK government guidance, part of the wider All Our Health framework, aimed primarily at healthcare professionals to support conversations with patients about eating and activity habits. It's evidence-based guidance rather than a public-facing programme, intended to help professionals have informed, consistent conversations. Among the points it references, losing at least 5% of current body weight is commonly cited in clinical guidance as a benchmark associated with meaningful health improvement, though what's appropriate for any individual is properly determined through an individual clinical assessment, not a fixed number applied universally.

While this particular resource is written for professionals rather than the public, it's worth knowing it exists, since it reflects the kind of evidence-based thinking that should genuinely be behind any conversation you have with a GP or prescriber about your own weight, even if you never read the document itself.

How to Prevent Obesity in Adults

Prevention in adults centres on sustainable, ongoing habits rather than short-term restriction: a moderate, consistent approach to diet and activity, built into daily life rather than treated as a temporary intervention. Building activity into an existing routine, prioritising consistent sleep, and managing stress all play a genuine, evidenced role alongside diet itself. For a fuller, practical breakdown of what genuinely helps, see our guide to healthy ways to reduce body weight.

When to Seek Support

If lifestyle changes alone aren't achieving a healthy result, or if you have a weight-related health condition, it's worth discussing your options with a GP or a UK-registered prescriber. Support genuinely spans a range, from structured lifestyle programmes through to medically supervised treatment for people who meet the clinical criteria, following an individual assessment.

Starting Treatment in the UK

The online consultation process

Where medically supervised treatment is appropriate, it starts with an online health questionnaire covering your medical history, current health and weight management goals, along with a BMI check as part of a fuller individual assessment. This is reviewed individually by a UK-registered prescriber, who will only approve treatment if it's judged clinically appropriate for you.

Pricing

Pricing varies by treatment type and is shown on the relevant product page. Check the current product page for the latest pricing before ordering.

Safety Considerations

This page deliberately avoids specific dietary or weight-loss-rate targets, since responsible personalisation depends on an individual clinical assessment, which a GP or prescriber can properly carry out. If you notice your relationship with food, eating or your weight feels distressing, preoccupying, or hard to control, that's worth raising with a GP.

Medical Disclaimer

This content is provided for general information purposes only and does not constitute medical advice. It is not a substitute for a consultation with a qualified healthcare professional. Treatment suitability depends on an individual clinical assessment carried out by a UK-registered prescriber. Results vary between individuals. If you have concerns about your weight or general health, speak to a pharmacist or prescriber.