Inflammatory processes are involved in the pathogenesis of the most common chronic non-communicable diseases and may also play an important initiating role in their development. Only recently have inflammatory markers been included in epidemiological studies focusing on nutritional status, body composition and physical activity. We are just starting to understand how different lifestyles can determine basal levels of inflammatory biomarkers in early ages. This review aims to summarise what is known about the relationships between lifestyle-related determinants (focusing on overweight, physical activity and dietary habits) and inflammatory markers in apparently healthy young populations. Obesity is the most widely studied determinant. Several large-scale studies have now demonstrated that healthy young subjects with more body fat or higher BMI have moderately higher concentrations of inflammatory markers than their leaner peers, supporting the idea that obesity should be considered as a state of chronic low-grade inflammation. Less data is available to allow us to elucidate how physical activity/fitness or dietary patterns may have a direct effect on inflammation in apparently healthy, disease-free young populations.