Facts about overweight and obesity

(Adapted from: Healthy weight, Healthy Living. A toolkit for developing local strategies. www.doh.org.uk)

How do we define overweight and obesity?

Measuring excess weight
Overweight and obesity in children and adults are commonly assessed by using Body Mass Index (BMI), which is defined as the person’s weight in kilograms divided by the square of their height in metres (kg/m2). A normal BMI is below 25kg/m 2, overweight 25-29.9kg/m 2 and obesity 30kg/m 2 and above.

In adults the waist circumference measurement is also used to assess a patient’s abdominal fat content or ‘central’ fat distribution. Males have an increased health risk with a waist circumference of 94cm (37 inches) or more and females with a measurement of 80cm (31 inches) or more. More than 102cm and 88cm respectively, ‘greatly’ increases the health risk.

How common is overweight or obesity?

In England, according to the latest figures (2006), 23.7% of men and 24.2% of women are obese and almost two-thirds of all adults (61.6%) – approximately 31 million adults – are either overweight or obese. The proportion who are severely (morbidly) obese (with a BMI over 40kg/m2) is 1.5% in men and 2.7% in women.

There has been a marked increase in the levels of obesity (BMI above 30 kg/m 2). Between 1993 and 2006, the proportion of men classified as obese has increased by 89% and of women by 54%.

By 2015, it has been estimated that 36% of men and 28% of women in England will be obese and by 2025, this may rise to 47% of men and 36% of women.

The proportion of children and young adults who are obese in the under 20 age group will rise to approximately 15% in 2025 (with slightly lower prevalence in boys than in girls). By 2050, it is estimated that 25% of the under-20 year olds will be obese.

Studies have shown that the higher a child’s BMI (kg/m2) and the older the child, the more likely they will be an overweight or obese adult. Furthermore, research has demonstrated that the offspring of obese parents have a greater risk of becoming overweight or obese adults, increasing the likelihood of developing health problems later in life.

What are the health risks of being overweight or obese?

Premature mortality

It has long been known that obesity is associated with premature death. Obesity increases the risk of a number of diseases including the two major killers – cardiovascular disease and cancer. It is estimated that, on average, obesity reduces life expectancy by between 3 and 13 years – the excess mortality being greater the more severe the obesity and the earlier it develops.

Obesity-related morbidity

The following are between 1 and 2 times more likely to occur with obesity:

• Colon cancer, breast cancer in postmenopausal women, womb cancer
• Reproductive hormone abnormalities
• Polycystic ovary syndrome
• Impaired fertility
• Low back pain
• Higher anaesthetic risk
• Foetal defects associated with maternal obesity

The following are between 2 and 3 times more likely to occur with obesity:

• Coronary heart disease
• Hypertension
• Stroke
• Osteoarthritis (particularly weight bearing joints)
• High levels of uric acid associated with the risk of gout
• Psychological issues (see box below)

The following are at least 3 times more likely to occur with obesity:

• Type 2 diabetes
• Insulin resistance
• Gallbladder disease
• Disorder of lipids including cholesterol
• Breathlessness (see box below)
• Sleep apnoea (disturbed pattern of breathing with short periods of absent breathing)

Note: All relative risk estimates are approximate. The relative risk indicates the risk measured against that of a non-obese person of the same age and sex. For example, an obese person is two to three times more likely to suffer from hypertension than a non-obese person. Source: Adapted from World Health Organization, report series 894(G) 1-253. Geneva WHO, 2000

Some of these problems appear in childhood, while others appear in early adulthood as a consequence of childhood obesity. The most important long-term consequence of childhood obesity is its persistence into adulthood. This may be followed by the early appearance of obesity-related disorders and diseases normally associated with middle age, such as type 2 diabetes and hypertension.

In older people, mechanical disorders such as back pain and arthritis are frequently associated with increasing body weight. The risk of disability attributable to osteoarthritis is equal to the risk of disability attributable to heart disease, and is greater than for any other medical disorder of the elderly.

Breathlessness

Breathlessness on exertion is a very common symptom in obese people. For example, in a large survey, 80% of obese middle-aged subjects reported shortness of breath after climbing two flights of stairs compared with only 16% of similarly aged non-obese controls, and this was despite smoking being significantly less frequent in the obese group.

In another study of patients with type 2 diabetes, one-third reported troublesome shortness of breath and its severity increased with BMI. Importantly, breathlessness in the obese may be due to any of several factors including co-existent (but often obesity-related) cardiac disease, unrelated respiratory disease or the effects of obesity itself on breathing.

Psychological issues

Psychological damage caused by overweight and obesity is a huge health burden. In childhood, overweight and obesity are known to have a significant impact on psychological wellbeing, with many children developing a negative self-image, lowered self-esteem and a higher risk of depression. In addition, almost all obese children have experiences of teasing, social exclusion, discrimination and prejudice.

In adults, the consequences of overweight and obesity have led to clinical depression, with rates of anxiety and depression being three to four times higher among obese individuals. Stigma is a fundamental problem. Many studies have reported widespread negativity regarding obese people, particularly in terms of sexual relations. The psychological experiences of overweight and obesity are extremely complex and are linked to culture and societal values and ‘norms’.

What are the benefits of losing weight?

Weight loss in overweight and obese individuals can improve physical, psychological and social health. There is good evidence to suggest that a moderate weight loss of 5-10% of body weight in obese individuals is associated with important health benefits, particularly in a reduction in blood pressure with a reduced risk of developing type 2 diabetes and coronary heart disease.

Look at some of the benefits of losing just 10kg of weight

• Improved lung function with reduced breathlessness and frequency of sleep apnoea (short periods of absent breathing).
• Improved insulin sensitivity (insulin levels rise with obesity probably due to a resistance to its effects).
• Improved ovarian function (and therefore fertility which may be adversely affected by obesity)
• Reduction in back and other joint pain.
• Improved lipid profile with:
• A 10% fall in total cholesterol, 15% fall in low density lipoprotein (LDL) cholesterol (the ‘bad’ cholesterol) and 30% fall in the triglyceride level
• An increase of 8% of high density lipoprotein (HDL) cholesterol (the ‘good’ cholesterol)
• A 50% reduction in fasting glucose in newly diagnosed diabetics
• A significant fall in blood pressure (10mmHg for systolic and 20mmHg for diastolic blood pressures)
• A significant reduction in mortality specifically:
• More than a 20% fall in total mortality and a 30% fall in diabetes-related deaths
• More than 40% fall in obesity-related cancer deaths

Adapted from Jung 2003 and Mulvhill and Quigley1997