Objective:To investigate the metabolic profile of fatty acids in elderly frail patients, and its value as a biomarker of frailty.Methods:Forty-nine older adults were recruited, of whom 19 were non-frail while 15 were in the pre-frail or frail phase.Targeted metabolomics was used to detect the serum levels of fatty acids, concerning 38 short-, medium-and long-chain fatty acids.Results:Metabolomics indicated elevated levels of 9 long-chain fatty acids in the serum of the elderly frail patients, with a 1.056-fold increase in the risk of fatigue for every 1 unit increase in the level of HOMO-γ-linolenic acid( OR=2.056, P=0.016). No metabolic differences were found between the pre-frail and non-frail groups.Three and seven long-chain fatty acids were negatively correlated with the grip strength and gait speed, respectively.The γ-linolenic acid was positively correlated with body mass index(BMI), percent body fat, visceral fat area and other indicators reflecting adipose tissue.However, no correlation was found between skeletal muscle, laboratory indicators or fatty acids.Five metabolic pathways were correlated with frailty, namely fatty acid biosynthesis, fatty acid metabolism, fatty acid elongation in mitochondria, linoleic acid metabolism and α-linolenic acid metabolism. Conclusions:Nine unsaturated fatty acids, including HOMO-γ-linolenic acid and γ-linolenic acid, may be potential biomarkers of frailty in the elderly.However, the value of fatty acid metabolomics for identifying pre-frail elderly people needs to be further investigated.