Metabolomic characterization of unintentional weight loss among community-dwelling older Black and White men and women

This study aims to understand the metabolic mechanisms of unintentional weight loss in older adults. We investigated plasma metabolite associations of subsequent weight change over 2 years in 1536 previously weight stable participants (mean age 74.6 years, 50% women, 35% Black) from the Health, Aging and Body Composition (Health ABC) Study. Multinomial logistic regressions were used to examine associations of the 442 metabolites with weight loss with/without an intention and weight gain >3% annually relative to weight stability. The metabolite associations of unintentional weight loss differed from those of intentional weight loss and weight gain. Lower levels of aromatic amino acids, phospholipids, long-chain poly-unsaturated triglycerides, and higher levels of amino acid derivatives, poly-unsaturated fatty acids, and carbohydrates were associated with higher odds of unintentional weight loss after adjusting for age, sex, race, and BMI categories. Prevalent diseases attenuated four and lower mid-thigh muscle mass and poorer appetite each attenuated 2 of 77 identified metabolite associations by >20%, respectively. Other factors (e.g., energy expenditure, diet, and medication) attenuated all associations by <20%. While 16 metabolite associations were attenuated by 20%-48% when adjusting for all these risk factors, 47 metabolite associations remained significant. Altered amino acid metabolism, impaired mitochondrial fatty acid oxidation, and inflammaging implicated by identified metabolites appear to precede unintentional weight loss in Health ABC older adults. Furthermore, these pathways seem to be associated with prevalent diseases especially diabetes, lower muscle mass, and poorer appetite.