Assessment

BMI alone is not a sufficient predictor of the detrimental effect of obesity.

Body Mass Index (Kg/m2)	WHO Classification	Popular Description
Less than 18.5	Underweight	Thin
18.5-24.9	Normal weight	Healthy normal weight
5.0-29.9	Grade 1 overweight	Overweight
30.0-39.9	Grade 2 overweight	Obese
40.0 or greater	Grade 3 overweight	Morbidly obese

Body Mass Index (BMI) is defined as weight divided by height² where weight is measured in kilograms, height in meters. The WHO Expert Committee on overweight has classified 5 BMI ranges for general use.

Assessments such as girth-height ratio (GHR) (waist circumference divided by height) give a measure of central obesity, which is associated with an increased risk of cardiovascular morality, hypertension, and non-insulin dependcnt diabetes. GHR has been shown, in prospective studies, to be a better predictor of cardiovascular risk than BMI.(5). Central obesity (waist circumference greater than 40 inches (102 cm) in males, greater than 35 inches (88 cm) in females) increases excess morality and risk of diabetes, heart attacks, and some forms of cancer. Weight gain after the age 18-20 also predicts increased risk. A weight gain of more than 1kg per year signals high risk. Finally, a sedentary lifestyle by itself increases mortality rates from all causes. (1)

Equations to calculate body composition and levels of waist circumference

Calculation of height in cm from lower leg length:

MEN Height =(2.31 x LLL) + 51.1

WOMEN Height = (1.84 x LLL) + 70.2

THIS CALCULATION SHOULD BE USED FOR PEOPLE WHO CANNOT HAVE ACTUAL HEIGHT MEASURED EG: WHEELCHAIR BOUND.

Calculation of percentage of body fat from waist circumference and triceps skinfold thickness:

MEN 0.353 waist (cm) + 0.756 triceps (mm) + 0235 age (y) - 26.4

WOMEN 0.232 waist (cm) + 0.657 triceps (mm) + 0.215 age (y) - 5.5

Catherine Hankey

Any assessment should include (see also medical assessment):

Medical history, risk factors and complications.
Weight history
Previous treatments
BMI and waist/hip ratio
Family history of related diseases and risk factors
Eating behaviour pattern
Diet history
Activity and lifestyle
Relevant social history

High risk groups (5)

Children in families where one or more parents are overweight or obese
Social class and level of education
Ethnic groups: South Asians are at greater risk compared to Afro-Caribbeans and Caucasians.
People with learning disabilities such as Down's Syndrome.
Smoking cessation is another important risk factor for weight gain.

Medical Assessment

Body Mass Index
Waist Circumference
Risk Status
Disease conditions:	Established CHD Other atherosclerotic disease Non-insulin dependent diabetes Sleep apnoea
Other obesity associated diseases:	Gynaecological abnormalities Osteoarthritis Gallstones
Cardiovascular risk factors (high risk if 3 or more):	Cigarette smoking Hypertension Cholesterol levels Family history
Other risk factors:	Physical inactivity High serum triglycerides
Eating behaviour pattern:	Diet history Binge eating Vomiting/laxatives Fat intake
Relevant social history:	Finance
Motivation
Previous treatments
Psychological factors:	Mood Anxiety
Family history
Endocrine status	Cushings syndrome Hyperprolactinaemia
Medication

Psychological Assessment

Assessment should include any relevant psychological factors in particular triggers for over eating such as stress, eating in response to low mood or interpersonal conflict. It is also important to check for psychological consequences of over eating and obesity such as body image disparagement (hatred and disgust of the body) body image distortion (perceiving the body to be much larger than it really is, or conversely failing to recognise how large the body is) and low self esteem. People who suffer from body image disparagement and low self-esteem in relation to eating and weight problems are very likely to go on to suffer from depression, and this possibility should also be considered.

The presence of an eating disorder such as binge eating disorder or bulimia should also be investigated by checking out whether the person suffers from loss of control over eating during which they eat a very large amount of food in a short space of time and whether following this they try to cornpensate by purging behaviour such as self induced vomiting or abuse of laxatives, excessive exercising or attempting to starve themselves for many hours.

Where a psychological problem such as binge eating or bulimia is identified, a referral to secondary mental health services should be considered (see below).

Underweight clients

Where BMI is below 17, the possibility of anorexia nervosa should be explored. As this is a life threatening condition, psychiatric or psychological referral should be urgently sought.