Abstract‘Obesity’ has, for decades, been a subject of intense scientific and public interest, and remains a key target for postgenomic science. I examine the emergence of determinism in research into ‘obesity’ in the postgenomic field of metabolomics. I argue that determinism appears in metabolomics research in two ways: firstly, fragmentation and narrow construal of the environment is evident in metabolomics studies on weight loss interventions, resulting in particular features of the environment (notably, dietary intake) having outsized influence while the wider (...) social environment is neglected. Secondly, studies aiming to characterize the metabolic signature of ‘obesity’ are guided by a commitment to a deterministic connection between ‘obesity’ and dysfunction, leading to a neglect or distortion of metabolic heterogeneity across individuals regardless of body size. (shrink)