Obesity may be caused by greater rates of bile acid activity in the digestive system, according to preliminary results of a University of Queensland study.
Preliminary findings of a two-year study by Medicine Department senior lecturer and gastroenterologist at the Mater Misericordiae Hospital, Dr Timothy Florin, show bile acid turnover (the rate at which bile acid is produced, lost and recycled in the body) is heightened in people classified as obese regardless of the type or amount of food consumed.
The increased rate means their absorption of fat could be more efficient than in people not classified as obese.
The finding sheds light on the metabolic activity of obese people and aids understanding of a condition affecting 20 percent of Australians.
Dr Bill Fong from the Royal Brisbane Hospital's Department of Nuclear Medicine, Mater Misericordiae Hospital research assistant Helen Woods and dietitian Kristine Simpson were also involved in the study monitoring 30 subjects with an average age of 37.
Bile acid is needed by the body to dispose of cholesterol and absorb fat. It is synthesised in the liver and concentrated in the gall bladder until a fatty meal is consumed. Bile acids are then released to facilitate absorption of fats as they pass through the small intestine. Most bile acid is then re-absorbed by the small intestine and via the liver stored in the gall bladder but some is lost to the colon.
For the study, volunteers consumed a harmless radioactive tracer which allowed bile acid's progress to be tracked every second day using a gamma camera.
Subjects were first assessed for their Body Mass Index (BMI) which measures obesity by comparing a person's height and weight. Readings of greater than 28 in women and 25 in men are considered obese.
The subjects, with BMIs ranging from 18 to 37, also recorded all food eaten during the period and the food's weight.
'We found that the rate of bile acid turnover in the obese subjects was increased regardless of the type and amount of food eaten,' Dr Florin said.
'The result is surprising given the body's usual counter reaction to abnormal conditions. In other words, it would be expected that the body of an obese person would react and adapt to the obesity by becoming less, rather than more efficient at absorbing fat.'
Dr Florin said further study was needed to pinpoint the reason for the greater bile acid turnover in obese people.
'It could be that the greater bile acid turnover has caused the obesity as these people are more efficient at absorbing fat,' he said.
He said the finding provided evidence that obesity was not entirely related to environment, that is factors within a person's control such as diet and exercise.
'Obesity is a serious problem in Australia associated with many potentially fatal diseases such as diabetes, hypertension, coronary artery disease, bowel and breast cancers,' Dr Florin said.
For more information, contact Dr Florin (telephone 3840 8906 or 3840 8014).
