Excess weight and obesity (adults)

Content last reviewed: July 2017


Preventing excess weight and obesity is a societal challenge, similar to climate change, and reducing population levels of overweight and obesity is one of the greatest health challenges that we face. It requires partnership between government, science, business and civil society, including at personal, family, community and population level (1).

Although there is no statistical difference in the level of excess weight for adults between England (64.8%) and Central Bedfordshire (67.1%) for 2015/16 (2), this figure indicates that most people are overweight or obese in Central Bedfordshire. People who are overweight have a higher risk of getting type 2 diabetes, heart disease and certain cancers. Excess weight can also make it more difficult for people to find and keep work, and it can affect self-esteem and mental health.

The causes of excess weight and obesity are extremely complex encompassing biology and behaviour. Although personal responsibility plays a crucial part in weight gain, human biology is being overwhelmed by the effects of today’s ‘obesogenic’ environment, with its abundance of energy dense food, motorised transport and sedentary lifestyles. As a result, the people of the UK are becoming heavier simply by living in the Britain of today. This process has been coined ‘passive obesity’. For the majority of people excess weight gain is the result of eating more calories than needed and/or undertaking too little physical activity to match calorie intake.

Overweight and obesity are clinical terms that describe a level of body fat which can lead to increasingly adverse effects on health and wellbeing. Levels are typically determined via Body Mass Index (BMI). This measures weight (kg) divided by height (m) . The value given places an adult into one of the following categories:

BMI Range


<18.5 Underweight

18.5 - 49.9

18.5 - 23

Health weight (white European)

Health weight (Asian)

25 - 29.9

23 - 27.5

Overweight (White European)

Overweight (Asian)

30 - 34.9


Obesity I (White European)

Obsity I (Asian)

35.9 - 39.9 Obesity II
>40 Obesity III (Morbidly obese)

Table 2: Source: NICE Clinical guidance reference guide 2 obesity. Published December 2006.

For Asian populations risk of adverse effects appears to begin from a BMI value of 23 - this is lower than the value for White Europeans (3).

In adults BMI is sufficiently reliable and the definitions are universally accepted.

BMI is not a direct measure of body fat. High levels of muscularity may suggest overweight or even obesity, however, this is unusual in the UK adult population. Suspect BMI values may be validated by measuring waist circumference and comparing the two values to decide overall risk.

Assessing risks from overweight and obesity

BMI classification

Waist circumference


Men low ≤ 94cm

Women low ≤ 80cm

White European men high. Asian men very high. 94 – 102 cm


White European women high. Asian women very high. 80-88cm

White European men very high. ≥102cm

Women very high ≥88cm

Normal weight 18.5 – 25 BMI

No increased risk

No increased risk

Increased risk

Overweight 25 – 30 BMI

No increased risk

Increased risk

High risk

Obesity I 30 – 35 BMI

Increased risk

High risk

Very high risk

Obesity II 35 – 40 BMI

Very high risk

Very high risk

Very high risk

Obesity III 40 BMI or more

Very high risk

Very high risk

Very high risk

Risks associated with excess weight

Excess weight is about health, not appearance.

Conditions linked with excess weight in adults and the associated lifestyle choices include:-

  • Cardiovascular disease
  • Respiratory conditions
  • Insulin resistance and Type 2 diabetes
  • Certain Cancers
  • Musculoskeletal problems
  • Low self-esteem and depression
  • Psychological and social problems such as stress, stigma, prejudice and bullying.

There is an exponential rise in risk as excess weight levels increase. As a result, development of excess weight in middle age shortens life expectancy on average by 2 to 4 years, or by 8 to10 years in those who become morbidly obese (4).

When compared to healthy weight individuals we can show what the effects could be.

An obese man (above 30 BMI) is:

  • 5 time smore likely to develop type 2 diabetes
  • 2.5 times more likely to develop high blood pressure, a major risk factor for sroke and heart disease.
  • 3 time smore likely to develop cancer of the colon.

An obese women (above 30 BMI) is:

  • 13 times more likely to develop type 2 diabetes
  • 4 times more likely to develop high blood pressure
  • 3 times more likely to have a heart attack
Predicted increase in diseases attributable to rising BMI levels, 2005-35

Predicted increase in diseases attributable to rising BMI levels, 2005-35. Table 6: shows the Increase in age- and gender-standardised incidence of diseases attributable to rising BMI levels, from 2005- 2035.

It is possible to estimate the disease specific attributable proportion of excess weight and obesity, that is, the proportion of a population with a given disease who would not have that disease if they were not obese.

  Hypertension CVD Diabetes
Disease specific attributable proportion (%) 24.1 20.2 24.1
Central Bedfordshire attributable population 8,818 4,084 2,794

Source: QMAS data 2011.

The proportion of chronic disease that is attributable to excess weight and obesity will increase substantially: this will in turn lead to high levels of sickness absenteeism and increased levels of poor mental health (5)

Maternal excess weight is associated with increased morbidity and mortality for both the woman and her unborn child (6). Pregnant women who have high levels of excess weight are at increased risk of:

  • Developing temporary diabetes of pregnancy
  • Having a raised blood pressure and pre-eclampsia
  • Having a blood clot in their legs (DVT)
  • Having a large or ill baby needing increased monitoring which can lead to complications in labour
  • Having a Caesarean section
  • Difficulty in siting for an epidural or giving anaesthetic
  • Having a wound infection, leading to a longer hospital stay
  • (Rarely) having complications following surgery and delivery requiring intensive hospital care
  • Having a still birth or intra uterine death

(Bedford Hospital NHS Trust Maternity data 2011)

The first study of Maternal Obesity in the UK was published in 2010 and states that ‘The East of England Strategic Health Authority had the highest overall rate of women with a BMI ≥35 at any point during pregnancy, and also the highest prevalence of each obesity category (BMI 35-39.9, BMI 40-49.9, BMI ≥50).’ The UK prevalence of BMI ≥35 was 4.99% (7)(local data not available)



(1) Foresight: Tackling Obesity Future Choices 2nd edition-Modelling future trends in Obesity and their impact on Health. Gov office for Science 2012.

(2) PHE Health profile for Central Bedfordshire 2015.

(3) CHOO V, 2002, WHO reassesses appropriate BMI for Asian population. The Lancet 20, 360 (9328):225

(4) Observatory NO.Briefing note:Obesity and life expectancy. Oxford, UK: NOO; 2010

(5) McPherson, K., Marsh, T. and Brown, M. 2007. Modelling Future Trends in Obesity and the Impact on Health. Foresight Tackling Obesities: Future Choices)

(6) Saving Mothers Lives 2003-2005. London: CEMACH; 2007

(7) ‘Maternal Obesity in the UK’ published Dec 2010 by Centre for Maternal and Child Enquiries.


Last updated Wednesday, 12th July 2017