Obesity Defined as Excess Storage of Inert Triglycerides – Do We Need a Paradigm Shift?

Obesity affects three domains of individual life: the physical effects of the body size and weight, the psychosocial effects of the abnormal body image and the various metabolic effects predisposing to a broad panel of co-morbidities. In this editorial, I will argue for the need of a fundamental revision of the concept of obesity as a health problem primarily in the latter domain. The argument is based on the accumulating evidence that the stored triacylglyceride (TAG) is an inert biochemical compound making the body fat an innocent bystander [1]. The metabolic health problems appear avoidable as long as the TAG stores can be expanded and emerge only when the limits are reached [2, 3]. This argument may elicit a need for new lines of research that can provide the basis for another definition of the obesity problem and hence for novel strategies for prevention and management of the condition and its associated health problems. Owing to the various ways of relationships between the three domains, a new definition based on the metabolic problems may have implications also for the two other domains. While acknowledging that there is a very well established association between accumulation of TAG in various body compartments and the metabolic health effects [4, 5], there are reasons to dissociate these observations from an interpretation of a causal relationship between TAG accumulation and the health effects. The immediate major reason to challenge the conventional idea of the impact of the amount of the accumulated TAG is the fact that there are individual deviations from the association with the metabolic alterations and with the risk of the clinical problems, i.e. the deviations that make the correlations less than 1.0. Although such departures are still compatible with a causal role of TAG, the complete disconnections in extreme scenarios raise serious doubts. The classical epidemiological problem of unknown confounding may apply here; the association of TAG accumulation with metabolic alterations may be due to other factors inducing these alterations and co-occurring with the TAG accumulation.