Skip to Main Content




Persons who are naturally very fat are apt to die earlier than those who are slender.



Obesity is the most common nutrition-related disorder in the Western world; as Tunnessen puts it, ‘Obesity is the most common form of malnutrition in the United States’.1 Most overweight adults and children who are obese have exogenous obesity, which tends to imply that ‘they ate too much’, but the problem is more complex than relative food input. Physical activity and environmental and genetic influences must also be taken into account. However, only a small percentage (4–6%) of human obesity is thought to be due to a single gene mutation.2 There is still a persisting tendency of affected families to blame ‘glandular’ problems as a cause of obesity. It is now considered that there is a strong genetic basis to obesity and that attributing it to overeating and lack of exercise is an overly simplistic viewpoint.


Key facts and figures

  • Two-thirds of the Australian population are overweight or obese and only 2–4% underweight.3

  • Abdominal obesity gives a higher cardiovascular risk at any weight.

  • The onset of obesity can occur at any age.

  • Secondary or pathologic causes are rare.

  • Less than 1% of obese patients have an identifiable secondary cause of obesity.2

  • Two conditions causing unexplained weight gain that can be diagnosed by the physical examination are Cushing syndrome and hypothyroidism.

  • After pregnancy, obesity may result from a failure to return to prepartum energy requirements.

  • Even small weight losses are effective in preventing diabetes and improving the cardiovascular risk profile.4


A diagnostic approach


A summary of the diagnostic strategy model is presented in Table 78.1.

Table Graphic Jump Location
Table 78.1

Weight gain: diagnostic strategy model


Probability diagnosis


The outstanding cause of weight gain in exogenous obesity is excessive calorie intake coupled with lack of exercise. This is determined largely by environmental influences. Overweight people often deny overeating but the true situation can be determined by recording actual food intake and energy expenditure, and by interviewing reliable witnesses.


Serious causes not to be missed


It is ...

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.


About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

Murtagh Collection Full Site: One-Year Subscription

Connect to a suite of general practice resources from one of the most influential authors in the field. Learn the breadth of general practice, including up-to-date information on diagnosis and treatment, as well as key clinical skills like communication.

$145 USD
Buy Now

Pay Per View: Timed Access to all of Murtagh Collection

48 Hour Subscription $34.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.