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What is obesity?

According to the World Obesity Federation; “Obesity is a medical condition described as excess body weight in the form of fat. When accumulated, this fat can lead to severe health impairments.”

Commonly, Body Mass Index, which takes into account your height and weight, is used to determine if someone is a healthy weight. For most adults, a BMI of:

  • 18.5 to 24.9 - healthy weight
  • 25 to 29.9 - overweight
  • 30 to 39.9 - obesity
  • 40 or above - severely obesity

However, BMI is a very crude measure, and is not used on its own to diagnose obesity. Other factors, such as you gender, ethnicity, body composition and age should be taken into account. You can use the NHS BMI calculator to check yours.

Other measures, such as waist circumference, can be used to diagnose whether someone is living with obesity and to assess their risk of developing other health condition such as Type 2 diabetes.

What causes obesity?

Obesity is a complex condition influenced by many factors. These include diet, activity levels, genetics (your DNA), other diseases or conditions, medications, mental health, sleep, weight stigma, poverty or your environment. In most cases it will be a combination of many these factors and is not simply driven by eating too much and not exercise enough.

The European Association for the Study of Obesity (EASO) and Obesity Canada have produced an infographic that explains the multitude of factors involved.

Critically, it is important not to just think of obesity as an issue of personal responsibility or failure. Helping the population to reach and maintain a healthy weight will require lots of different policy changes – there is no one solution that will have enough impact, it require the whole system to change.

Find out more about the BDA’s work on pushing for a comprehensive approach to managing and preventing obesity across the life course on our campaign pages.

What is the best way to lose weight?

There is no one best way to lose weight, which is why dietitians work to understand your personal circumstances when making recommendations. Improving your diet and increasing activity can be key to losing weight, although are not the only factors that need to be considered. 

When aiming to lose weight it is important to have realistic goals that are achievable. Success boosts confidence in your ability to lose weight. A weight loss of between 0.5 to 2 pounds (0.5-1kg) a week is a safe and realistic target.

There is no quick fix. People who successfully lose weight and keep it off develop techniques to make their new lifestyle and activity habits an enjoyable way of life and also make them life long.

Find out more about weight loss with the BDA Food Fact Sheet.

What is weight stigma?

Weight stigma, also known as weight bias, is the discrimination or stereotyping of a person based on their weight or body size.

Weight stigma can be damaging to mental health, increase metabolic risk factors and further reducing self-esteem. Weight stigma is unhelpful in supporting people to better manage their weight and has been shown in in fact result in increased calorie intake and increased body weight over time.

Read about the BDA’s efforts to reduce weight stigma in our own work.

How do dietitians support people living with obesity?

Obesity specialist dietitians work with adults and children, alongside their families, to form a plan for eating patterns, food, activity levels & wellbeing that takes into account personal goals, preferences and cultural needs. They often work with other healthcare professionals such as doctors, physiotherapists and psychologists. Other obesity dietitians research obesity and its treatment, or work in public health to provide population level advice to help people reach or maintain a healthy weight.

Find out more about the work of obesity dietitians from our Obesity Specialist Group

What are the “tiers” or “levels” of weight management?

This definition is adapted from the National Institute of Health and Care Excellence (NICE).

Different tiers or levels of weight management services cover different activities. Definitions vary locally but usually;

  • Tier 1 covers universal services (such as health promotion, public health services or primary care)
  • Tier 2 covers lifestyle interventions such as commercial weight loss programmes or seeing your GP or nurse for advice.
  • Tier 3 covers specialist weight management services for those that need more specialist support.
  • Tier 4 covers weight loss (bariatric) surgery.