Endocrine Abstracts

Background: Obesity is the excessive accumulation of adipose tissue to the extent that health may be impaired. Determination of the mechanisms governing adipose deposition and body weight regulation are now a scientific priority. High dietary fat intake is generally considered to be a factor in obesity’s multi-factorial aetiology and the metabolic syndrome. Yet not all dietary fats appear to be obese genic to the same degree.

Objective: To study the role of saturated (butter–milk) and polyunsaturated (fish–oil) dietary fats (DF) in the development of obesity.

Methods: Male Wistar rats were randomised (n=10 per group) to receive one of four experimental diets which contained either moderate amounts of DF (23% of dietary energy) as either butter–milk (23%B) or fish–oil (23%F), or high levels of DF (42% of dietary energy) as butter–milk (42%B) or fish–oil (42%F). Rats were given ad-libitum access to their respective diets for 84 days. Total body adiposity was measured in car casses by magnetic resonance spectroscopy (MRS).

Results: At termination, there were no significant differences in the energy intake or body weight gain between the 23%F and 23%B groups. Whilst body weights were not significantly different between the 42%F and 42%B groups, there was a significant reduction in the cumulative energy intake in the 42%F group (P<0.01). Despite similar body weights, preliminary MRS analysis showed a trend towards reduced total adiposity in the rats fed the 42%F diet compared to the 42%B group.

Discussion: At high dietary fat levels, rats fed a fish–oil enriched diet appear to exhibit an enhanced metabolic efficiency; they consume less energy but have equal body weight gain to those animals consuming an isoenergetic saturated-fat diet. However, MRS analysis suggests any enhanced efficiency does not cause an increase in total adiposity; rather a leaner and therefore a more metabolically favourable phenotype may prevail.