Figure 1. Altered energy balance leads to obesity and metabolic disorders.

(A) When the quantity of energy absorbed by an animal (i.e., food intake) equals its energy expenditure (i.e., physical activity/exercise), the result is a neutral energy balance that permits body weight stability. In this situation lipids are stored in white adipose tissue (WAT). (B) An imbalance in either food intake or energy expenditure leads to increased body weight and obesity. In this context, the storage capacity of WAT may become saturated, which redirect lipids to be accumulated in peripheral organs such as liver, muscle, and pancreas. In a first step, these lipids are accumulated as triacylglycerols (TGs). When the storage capacity of these tissues is also saturated, excess of lipids, enters in alternative non-oxidative pathways that results in production of toxic reactive lipid species (such as diacylglycerols and ceramides) leading to tissue-specific damage, a process known as lipotoxicity.