Healthy Eating
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BMI and Obesity

The Body Mass Index

In adults, obesity is defined using the Body Mass Index (BMI). BMI is calculated as weight in kilograms (kg) divided by height in metres squared (m2).

  • An ideal BMI is 20 to 25.
  • A BMI of 25-29.9 kg/m2 is overweight.
  • A BMI of > 30 kg/m2 is obese.
  • A BMI of ≥ 40 kg/m2 is morbidly obese meaning that weight is an impending threat to health.

For children their weight, amount of body fat and height are age related. Child growth charts are used to determine if they have a healthy weight.

Obesity levels by age and sex

According to the results of the Northern Ireland Health and Wellbeing Survey (NIRSA, 2005/06):

  • Obesity was most prominent amongst the middle aged. Almost a third (29%) of 45-54 year olds were obese, compared with 13% of those aged 16-24.
  • Men were more likely (64%) than women (54%) to be either overweight or obese.

Socio-economic differences in Obesity in UK

Obesity is seen to have more prevalence among unskilled manual occupations, particularly in women. Figures from the Department of Health in 2004, give an indication of the levels of obesity within the difference socio-economic groups:

  • 16% 'professional' males and females
  • 23% 'unskilled' males
  • 29% 'unskilled' females.

Obesity associated Health problems

Obesity is known to increase the risk of many diseases and conditions:

  • Diabetes Type II
  • Hypertension (increased B/P)
  • Coronary Heart Disease
  • Stroke
  • Gall bladder disease
  • Joint problems
  • Some cancers
  • Breathing problems and sleep apnoea
  • Lower back pain
  • Complications in pregnancy
  • Reproductive disorders
  • Complications in surgery
  • Psychological and social problems.

For a more complete discussion refer to the Chief Medical Officer's Report, 2002.

Overall outcomes of obesity for the individual and society

  • An increased illness burden in the population as a whole.
  • 6% of all deaths can be attributed to obesity
  • Shortens life by ~ 9years
  • Ill-health caused by poor diet costs the economy 2.5 billion / year
  • Increased costs for NHS / Tax payers

(DoH, 2004)

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