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Obesity - Management
How should I assess someone's risk of obesity-related health problems in the future?

  • Calculate the person's body mass index (BMI) if this has not already been done.
  • Measure waist circumference in people with a BMI less than 35 kg/m2.
  • Using this information and Table 1, assess whether the person is at increased risk of cardiovascular and metabolic complications. Although different cut-off points are generally not recommended for different populations, use clinical judgement for certain people — Asian people may be at higher risk and older people at lower risk for a certain BMI compared with the general population.
  • Ask about family history of diabetes (including gestational diabetes) and coronary heart disease.
Clarification / Additional information
  • For people with a body mass index (BMI) of less than 35 kg/m, waist circumference may be used as part of the risk assessment [NICE, 2006].
  • Waist circumference is used to assess the amount of abdominal fat a person has, otherwise known as 'central' fat distribution [National Heart Forum, 2007].
  • This should be measured around the midpoint between the lowest rib and the top of the right iliac crest [DH, 2006].
Table 1. Classification of waist circumference in people who are overweight or in obesity class I.
BMI
Low
High
Very high
Overweight (BMI 25–29.9)
No increased risk
Increased risk
High risk
Obesity I (BMI 30–34.9)
Increased risk
High risk
Very high risk
For men, waist circumference < 94 cm (37 inches) is low, 94–102 cm (37–40 inches) is high, and > 102 cm (approx 40 inches) is very high.
For women, waist circumference < 80 cm (31.5 inches) is low, 80–88 cm (31.5–34.5 inches) is high, and > 88 cm (approx 34.5 inches) is very high.
Data from: [NICE, 2006]
Basis for recommendation
  • This recommendation is based on guidance from the National Institute for Health and Clinical Excellence (NICE) on the prevention, identification, assessment, and management of overweight and obesity in adults and children [NICE, 2006], the care pathway for the management of overweight and obesity from the Department of Health [DH, 2006], and a review published in the Lancet [Haslam and James, 2005].
    • Life-threatening problems are more likely to occur as body fatness increases, therefore identifying at what body mass index (BMI) the health risks to a person increase is important [National Heart Forum, 2007].
    • Central obesity (assessed by waist circumference) is linked to higher risks of type 2 diabetes and coronary heart disease [National Heart Forum, 2007].
    • People who are overweight (BMI 25–29.9 kg/m2) with a waist circumference of more than 94 cm in men and more than 80 cm in women, or people classed as obesity I (BMI 30–34.9 kg/m2) have an increased risk of developing long-term health problems. This risk increases proportionally to the person's waist circumference [NICE, 2006].
    • If a person's BMI is equal to or greater than 35 kg/m2, waist circumference does not add a great deal to the measure of risk provided by the person's BMI [National Collaborating Centre for Primary Care, 2006].
    • The BMI of a person who is elderly has a lower correlation with their percentage body fat than in a young person, and is less strongly associated with cardiovascular morbidity. However, a reasonable correlation still persists [National Collaborating Centre for Primary Care, 2006].
    • People from certain socioeconomic and ethnic backgrounds may be at greater risk of obesity, or have different beliefs about what is a healthy weight and weight management [NICE, 2006].
    • Some ethnic groups (e.g. Asian people) have increased cardiovascular and metabolic risks at lower BMIs. There is no universal agreement whether the BMI classification should be adapted for this group [National Heart Forum, 2007]. However, NICE recommend that health professionals need to use clinical judgement when assessing risk factors in these groups of people [NICE, 2006]. The World Health Organization (WHO) have proposed BMI cut-offs for Asian adults of 18.5–22.9 kg/m2 for a healthy weight, and 23 kg/m2 or more for overweight: 23–24.9 kg/m2 (at risk), 25–29.9 kg/m2 (obesity I), and 30 kg/m2 or more (obesity II) [WHO International Association for the Study of Obesity and International Obesity Task force, 2000].
    • There is also no globally applicable grading system of waist circumference for ethnic populations, but the International Diabetes Federation (IDF) and the WHO have suggested waist circumference thresholds for Asian adults of 90 cm (35 inches) or more for men, and 80 cm (31 inches) or more for women (the IDF definition includes South Asian and Chinese populations only) [WHO International Association for the Study of Obesity and International Obesity Task force, 2000; International Diabetes Federation, 2005; National Heart Forum, 2007].

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