Go at least into the functionalist, conflict (political economy) and symbolic-interactive (cultural-individualist) perspectives to guide explanation. They make sure you keep to the sociology. However, the title wants a practical, historical approach, so you would not want to get bogged down in theory.
As in education, however, class outweighs gender and ethnicity in definitions of being well, the existence of illness. This insight might well be in the essay
|Class does not of itself imply the superiority of conflict theory or political-economy theory. Illness as sociological is relevant in functionalism, although functionalism implies a contract of obligation with the individual to remove the illness and this impacts on individual self-definition, or the importance of interactionism.|
Nevetheless, one focus is inevitably going to be on social class and economics:
Interactionism is important because its the labelling of illness as a form of deviance, and this matters if the evidence shows class disparities in illness and wellbeing. Dieting is an industry that ends up blaming largely working class individuals for weight gain and yet the food processing industry makes millions through cheap food that deskills the houseworker. It's cheaper not to cook yourself, but the cost is food processed with salt and sugar.
Use such historical examples framed by theory.