Page 511 - Medicine and Surgery

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Nutritional and 13

metabolic disorders

Nutritional disorders, 507 Metabolic disorders, 513

Nutritional disorders Aetiology
Most patients have simple obesity. Some conditions as-
sociated with obesity are as follows:
Obesity Drug-induced weight gain: Antipsychotic drugs, an-
ticonvulsant drugs, antidiabetic drugs and steroids.
Definition
Endocrine disorders may be associated with the de-
The World Health Organisation defines overweight and
velopment of obesity, such as Cushing’s syndrome,
obesity in terms of the body mass index (weight in
hypothyroidism and polycystic ovary syndrome.
kilograms divided by the square of height in metres
Obesity is characteristic of some congenital disor-
2
2
(kg/m )). A BMI over 25 kg/m is defined as overweight ders associated with hypogonadism, such as Prader–
2
and a BMI of over 30 kg/m as obese. Although these
Willi syndrome and Laurence–Moon–Bardet–Biedl
definitions are useful, the risk of disease in populations
syndrome.
increases progressively from lower BMI levels. A full
Simple obesity is likely to be a combination of genetic
consideration of obesity including prevention, identi-
and enviromental factors:
fication, evaluation, treatment and weight maintenance
Genetic factors: Studies of twins, adoption studies and
of overweight and obesity in adults is being conducted
family studies all suggest the existence of genetic fac-
by the National Institute for Clinical Excellence (NICE)
tors in human obesity. Animal studies particularly in
with a proposed publication in 2006.
mice have identified several gene defects inherited in
both dominant and recessive fashions that can cause
Prevalence obesity. Some correlates with human obesity have
Worldwidemorethan1billionadultsareoverweightand been identified, although the exact genetic basis re-
300 million of these are clinically obese. In England in mains unclear.
1998, 18–19% of individuals were clinically obese, a rate Prenatal influences and breast-feeding may influence
increasing dramatically. Prevalence increases by social obesity in childhood. Obesity in adolescence rather
class (15% in class I to 30% in class V). than earlier in childhood is a better predictor of adult
obesity.
Several factors that are associated with a high risk of
Age
obesity have been identified:
Prevalence increases by age up to 60–65 years.
Lowmetabolicrate,increasedcarbohydrateoxidation,
insulin resistance and low sympathetic activity.
Sex Lower socioeconomic class, lower education level and
F>M cessation of smoking.
507