Anorexia nervosa patients display a deficit in membrane long chain poly-unsaturated fatty acids.

BACKGROUND & AIMS: The energy deficit in anorexia nervosa (AN) results from a low energy and fat intake. Data from the literature are at odds about a deficiency in essential fatty acids (EFA), linoleic (LA) and alpha-linolenic (ALA) acid. The aim of the present study was to determine RBC phospholipid FA composition in AN patients, and to relate this FA profile to fat mass and BMI. We postulated that there should not be a deficit in EFA, because AN patients are in negative energy balance, and a significant supply of EFA arises from the lipolysis of AT triglycerides.

METHODS: Twenty-two AN women (14.2 ± 2.0 kg/m² BMI) had a DEXA-body composition analysis, and an analysis of FA composition in the phospholipids of red blood cell membranes by capillary gas chromatography. The control group was made of 25 healthy women.

RESULTS: There was no EFA deficiency in RBC, i.e. no decrease in LA and ALA, and no rise in C20:3 n-9. However, long chain poly-unsaturated FA (LC-PUFA), mainly those of the n-3 family were significantly reduced. A negative correlation was found between fat mass and ALA, with a critical fat mass close to 5 kg, under which ALA was dramatically increased.

CONCLUSION: AN patients display a complex membrane FA profile without traits of EFA deficiency but with a deficiency in LC-PUFA. We propose that adipose tissue is an endogenous source of FA able to compensate for the reduced food intake in EFA, but unable to provide enough LC-PUFA.