What is obesity?
The term obesity describes a person who has significant excess body weight. In the UK, it is estimated to affect around 1 in every 4 adults and around 1 in every 5 children aged 10 to 111.
For adults, the World Health Organization (WHO) defines overweight and obesity as follows2:
- Overweight: A body mass index (BMI) greater than or equal to 25; and
- Obesity: A BMI greater than or equal to 30.
BMI provides the most useful and accessible measure for the public of whether someone is classified as being overweight or living with obesity. This is because it is the same for all adults, regardless of sex or age. However, it should be considered a rough guide because it may not correspond to the same degree of body weight in different individuals2.
A better measure of excess fat is waist size, which can be used as an additional measure in people who have a BMI of 25 to 34.91. Generally, men with a waist size of 94cm or more and women with a waist size of 80cm or more are more likely to develop obesity-related health problems1.
What causes people to gain excess body weight?
Obesity is caused by a combination of genetics and lifestyle factors, and therefore diet and exercise alone are not always sufficient for weight loss.3 The cause and management of obesity is still greatly misunderstood, causing people living with obesity to feel as though they are to blame, and they continue to face stigma, bias and discrimination, all of which can have a significant impact on their mental health.4
- Obesity is a complex disease that can be caused by multiple factors. Up to 70% of weight health can be linked to genetics and it can also be influenced by physiological, psychological, environmental and socio-economic factors5
Our weight changes when energy intake is not equal to energy expenditure. This is referred to as our ‘energy balance’, and is influenced by many factors, some of which are outside of our control.
Biology: Up to 70% of the causes of obesity can be linked to genetics, family history and ethnicity.6 In some cases, genetics can increase the risk of a person developing obesity by 20–30%.6 Some medical conditions can cause people to gain weight – for example, conditions affecting the endocrine system can cause hormone imbalances that affect a person’s energy balance.7
Psychological wellbeing: some people eat more when they are tired, angry8 or stressed,7 or as a result of some common medications, e.g. antidepressants7
As a result, it’s not surprising that two people who exercise and eat equal amounts, will likely have different body shapes, and won’t lose weight at the same momentum. Identical twins could have entirely different eating habits and levels of exercise, but ultimately similar body weights due to their near-matching genetic make-up.
What are common health consequences of obesity?
It is crucial to take measures to tackle obesity because it can lead to several serious and potentially life-threatening conditions like1,2:
- Type 2 diabetes
- Coronary heart disease
- Some types of cancer, such as breast cancer and bowel cancer
- Musculoskeletal disorders, especially osteoarthritis
Besides your physical health, obesity can also affect your overall quality of life. This can lead to mental health problems, such as depression and low self-esteem1.
If you are thinking about weight loss the NHS weight loss plan is developed in collaboration with the British Dietetic Association. It has a 12 week diet and exercise weight loss plan and takes patients from step to step with tools like food and weight diaries.
If you have been unable to lose weight through lifestyle changes alone your healthcare professional may recommend medical treatment or, in some cases, weight loss surgery to help achieve your goals.
Obesity UK lists support groups aimed at supporting people to engage in physical activity and healthy eating with a significant focus on the emotional well-being of group members.
Perceptions of obesity
A lack of knowledge can also mean people with obesity are often subject to other stigmatising attitudes too, which can lead to inequalities at every life stage – from school through to the workplace.
There’s more to obesity than meets the eye. On top of the day-to-day challenges of obesity, and being exposed to hurtful, stigmatising comments, there may also be comorbidities – or associated conditions – to consider. Obesity is linked to around 200 other diseases.9 Some of those diseases are life-altering; others are life limiting.
One of the greatest impacts can be on mental wellbeing. Like other forms of stigmatisation (e.g. race, class, gender, ability etc.), weight stigma has been shown to increase the likelihood of developing mental health issues such as depression and low self-esteem.10 In fact, there is a reciprocal link between obesity and depression: people living with obesity exhibit a 55% increased risk of depression, and adults who have been diagnosed with depression have a 58% increased risk of developing obesity.11 Here in the UK, one in 20 cancers are caused by excess weight.12
- NHS. Obesity. May 2019. Available at: https://www.nhs.uk/conditions/obesity/ [Last accessed 24 March 2020].
- World Health Organization. Obesity And Overweight. March 2020. Available at: https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight [Last accessed 24 March 2020].
- Obesity: Causes. Available at: https://www.nhs.uk/conditions/obesity/causes/. Last accessed: September 2019
- Puhl RM, Heuer CA. The stigma of obesity: a review and update. Obesity (Silver Spring). 2009;17:941–964
- Genetics of Obesity. Available at: https://www.nhs.uk/news/obesity/genetics-of-obesity/ Last accessed: September 2019
- Obesity Prevention Source. Genes are not our destiny.
Available at: https://www.hsph.harvard.edu/obesity-prevention-source/obesity-causes/genes-and-obesity/ [Last accessed: February 2020].
- NHLBI. Overweight and obesity – Causes Available at:
http://www.nhlbi.nih.gov/health/health-topics/topics/obe/causes [Last accessed: February 2020].
- Wright and Aronne. Causes of obesity. Abdom Imaging.2012;37:730–732.
- Yuen M, Earle R, Kadambi N, et al. A systematic review and evaluation of current evidence reveals 195 obesity-associated disorders. Poster abstract presentation at: The Obesity Society Annual Meetingat ObesityWeek 2016; Oct. 31 – Nov. 4, 2016; New Orleans.
- Puhl RM, Heuer CA. The stigma of obesity: a review and update. Obesity (Silver Spring). 2009;17:941–964.
- Luppino FS, de Wit LM, Bouvy PF, et al. Overweight, obesity, and depression: a systematic review and meta-analysis of longitudinal studies. Arch Gen Psychiatry. 2010;67:220-229.
- Cancer Research UK. Does obesity cause cancer?
https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/obesity-weight-and-cancer/does-obesity-cause-cancer [Last accessed:February 2020].