We investigated adipose tissue fatty acid composition in 22 moderately to severely malnourished patients with cirrhosis and in 22 healthy volunteers by in vivo carbon-13 magnetic resonance spectroscopy (MRS). Gas-liquid chromatography (GLC) of adipose tissue samples was also performed in 11 of the patients and in 4 volunteers. In vivo13C magnetic resonance spectra were obtained from the subcutaneous adipose tissue before and after eight weeks following orthotopic liver transplantation (OLT). Adipose tissue biopsy samples were obtained for GLC analysis at the time of transplantation in the patients and at inguinal hernia repair in the 4 volunteers. No significant differences were found in the subcutaneous adipose tissue total-saturated, - polyunsaturated or -monounsaturated fatty acid composition between patients and healthy volunteers by in vivo13C MRS. GLC analysis of adipose tissue samples confirmed that total levels of saturated, poly-, and monounsaturated fatty acids remained the same but revealed significant differences in levels of individual fatty acids, particularly n-3 fatty acids (total n-3, cirrhotics: .84% ± .07% vs. controls: 1.36% ± .13%, P < .01). Eight weeks following transplantation, recipients showed a considerable increase in body mass (pretransplantation: 59.3 ± 3.2 vs. posttransplantation: 63.2 ± 3 kg, P < .01). 13C MRS revealed a significant increase in saturated fatty acids (pretransplantation: 21.6 ± 2.8 vs. posttransplantation: 25.5% ± 1.2%, P < .05) and a significant decrease in unsaturated fatty acids. The application of noninvasive MRS techniques may be important to identify the differential uptake of fats, examining both specific fatty acids and different body fat compartments. In the future, this may be useful in optimizing the dietary management of severely malnourished patients with chronic liver disease before liver transplantation.