The concept of lifestyle is commonly used as something that needs to be changed if we want to achieve a sustainable development. But what does the concept of lifestyle mean? How is it defined? Educators and politicians, among others, need a definition to use the concept and understand how it is related to sustainable development. This paper suggests a plural definition based on a level analysis. There are four levels, from individual to global, on which lifestyle can be understood. There is also an alternative definition on the individual level from a cognitive science perspective. We need to understand the concept of lifestyle at these levels to analyse the relationship to sustainable development problems. Perhaps we should not look at lifestyle as a problem per se, but at the problems used to elaborate a lifestyle.