Long TE 1H-MRS of fat results in an improved baseline and more narrow peaks but may be impacted by J-coupling effects. Here we compare long TE 1H-MRS of adipose tissue fat composition to gas chromatography-mass spectrometry (GC-MS) of adipose tissue biopsies. There was a close correlation between the two methods for both unsaturation =CH/CH2 (R = 0.719, P < 0.00001) and saturated chain length CH2/CH3 (R = 0.782, P < 0.00001). MRS overestimated unsaturation and underestimated saturated chain length. Long TE 1H-MRS allows assessment of adipose tissue fat composition, however correction factors are needed for comparison to other methodologies.