**2. Trait theories**

People often think about obesity in the same way they think about other physical or psychological traits: as a basic attribute that individuals possess to varying degrees. Dweck et al. [21, 22] have identified two opposing lay theories that characterize how people think and reason about a variety of traits, which are distinguished by the degree to which the trait is viewed as malleable [21, 22]. People who hold an "entity theory" of intelligence (also known as "fixed mindset"), for example, think about the intellect as something hard-wired and stable, while those who hold an "incremental theory" (also known as a "growth mindset") believe their intellectual abilities can grow through effort and hard work. Holding one of these theories is associated with a great deal of downstream behavior and cognition. For instance, incremental theorists are more committed to their learning goals and are more persistent in the face of adversity than people who think their intellectual abilities are fixed.

A recent study of dieters [23] found that people who hold incremental theories of obesity adopt qualitatively different strategies for losing weight compared to those who hold an entity theory of obesity. Consistent with prior research, incremental theorists were much more open to changing their lifestyle—to embrace a new diet, implement a novel exercise routine, or attend group meetings—in the service of achieving their weight-loss goal.
