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Since the beginning of the 20th century, the prevalence of infectious diseases has gradually decreased, while that of chronic diseases is growing exponentially: this phenomenon is known as the epidemiological transition. In this context, health is no longer to be understood as merely the absence of disease, but as a complex whole, also described as ‘environmental health’. Indeed our daily interactions with the environment in the long term are what will influence our health. Chronic diseases are difficult to cure: public health should no longer focus solely on care, but also and especially on prevention. Diet is particularly interesting in this context: it can be considered as a notable part of our interaction with the environment, on which each individual has the power to act, although under the constraint of economic factors and conditioned by culture. It can also be beneficial in preventing the development of chronic diseases, or harmful in promoting it. There are links between the growth of social inequalities in health and the prevalence of chronic diseases; the most socially disadvantaged populations are the most affected and are the greatest consumers of ultra-processed foods, which are identified as causing chronic diseases. Sociology can contribute to these issues by providing insight into the food and nutrition representations and behaviors of socially disadvantaged populations, ultimately to help develop appropriate prevention campaigns.