The Causes Of Obesity And How It Impacts Our Health

Among women, obesity is set to overtake smoking as biggest preventable cause of cancer.

Obesity is set to overtake smoking as the biggest preventable cause of cancer among UK women in 25 years’ time, according to a Cancer Research UK report.

Projections by the charity calculate that by 2035, 10% of cancers in women will be caused by smoking and 9% by excess weight. But by 2043, if trends continue as expected, excess weight in women could cause even more cases of cancer than smoking.

Predictions are different among men as a greater percentage smoke and are therefore more likely to have tobacco-related cancers, the charity said.

Dr Alison Tedstone, chief nutritionist at Public Health England (PHE), labelled obesity “the challenge of a generation” and said bold action is now needed to make a change.

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What Is Obesity?

Obesity refers to the amount of body fat a person is carrying and is typically determined based on a person’s body mass index (BMI) and their waist circumference.

While there are studies that suggest a person can be obese and healthy, there is also evidence to suggest it can increase the risk of conditions such as type 2 diabetes and cancer.

What Causes It?

Obesity is mostly caused by poor diet and lack of exercise, according to NHS Choices. However in a world where a healthy diet is, more often than not, expensive and our lives are increasingly sedentary (we spend on average nine hours a day sat down), it’s perhaps no surprise that one in four UK adults are obese.

Obesity Health Alliance lead Caroline Cerny blames environmental factors such as advertising and promotion of unhealthy food and drink for contributing to obesity, particularly among children.

It’s important to note there are other possible causes of obesity that don’t focus on diet and fitness. It can occur as a result of a genetic condition (such as Prader-Willi syndrome) or an underlying medical condition. For example, an underactive thyroid gland can cause weight gain, as can Cushing’s syndrome.

Some types of medication can also cause a person to gain weight, which can result in obesity. These include corticosteroids, epilepsy medication, diabetes medicine and some drugs used to treat mental illness.

How To Know If You’re Obese

Doctors tend to diagnose obesity in two ways. If a person has a BMI of 30 to 39.9 then they are classed as obese (a BMI of 40 or above is classed as ‘severely obese’). However there are exceptions to this rule as some people who are very muscular can have a high BMI.

The other measurement is waist circumference. The NHS suggests that men with a waist circumference of 94cm (37in) or more and women with a waist circumference of 80cm (about 31.5in) or more are more likely to develop obesity-related health problems.

Illnesses Linked To Obesity

Obesity has been linked to a range of health problems including type 2 diabetes, coronary heart disease and stroke.

In adults, it increases the risk of 13 different types of cancer including breast, bowel and kidney cancer, Cancer Research UK says. While more males than females are overweight or obese, obesity has a greater effect on women, as some of the most common obesity-related cancers predominantly affect them – such as breast and womb cancers.

People classed as obese might also experience symptoms that impact day to day life such as: breathlessness, increased sweating, snoring, difficulty doing exercise, lethargy, joint and back pain. They might also experience low confidence and self-esteem, and feel lonely.

Obesity has also been linked to health complaints like asthma; gastro-oesophageal reflux disease (GORD), which is where stomach acid leaks into the gullet; gallstones; reduced fertility; sleep apnoea; liver disease; kidney disease; and pregnancy complications.

The annual costs associated with obesity to the wider economy, the NHS and social care systems are estimated to be £27 billion, £6.1 billion a year and £352 million respectively, according to PHE.


Treatment for obesity tends to focus on diet and fitness. However, if caused by underlying health problems they also need to be addressed and doctors should make separate assessments to get to the bottom of the issue.

According to NHS Choices, GPs recommend a healthy, balanced diet and exercising regularly to treat obesity – although this can seem quite vague.

General advice around fitness is that people should be doing at least 150 minutes of moderate aerobic activity or 75 minutes of vigorous aerobic activity a week. In some cases, GPs might recommend weight loss groups or prescribe exercise (where you’re referred for fitness sessions with a trainer).

On the healthy diet front, PHE’s Eatwell Guide advises people to eat five portions of fruit and vegetables a day; base meals on starchy foods like potatoes, bread, rice or pasta; have some dairy or dairy alternatives; eat some beans, pulses, fish, eggs, meat and other protein; choose unsaturated oils and spreads (eating them in small amounts); and drink plenty of water.

People are also advised to eat fewer foods that are high in sugar, fat and salt. But this is a difficult ask for many families. A recent report by The Food Foundation found roughly 3.7 million children in the UK come from families earning less than £15,860 a year who therefore struggle to afford a healthy diet in line with government guidelines.