Roman diet has been extremely studied with the use of biochemical tools these last years. If first, studies tended to conclude at a standardization of the diet during this period, the last studies of population of Rome or other territories like Spain attests to a less uniformed diet across the empire. Historic and archaeological data support that northern continental fringes of the Empire was in the center of multiple cultural influence with the cohabitation of Gallic, Germanic and Roman population. Our study aims to understand if those particularities impact the diet. Using stable carbon and nitrogen isotope ratios, we choose to focus on (I) an urban population from one of the most important city of Belgica II Samarobriva (actual AmiensinFrance, n=91) to discuss the cohabitation of populations from different geographical origins and (II) three small rural populations (n=32, Roclincourt, Bettencourt, Duisans, France) to identify the impact of the economic and political structures of the society. Finally, a comparative analysis is attended between our French and contemporaneous Britain populations (n=475) to evaluate the impact of environmental factors and determine the specificity of Northern Gaul. Results show that within the urban population, the diet was highly variable with the presence of probable outsiders. The rural populations had diets different one from each other (the Bettencourt’s individuals had a larger variability of alimentary choice compare to Roclincourt and Duisans with a greater reliance on millet) and significantly different from the urban one (less input of animal proteins). To end, the general diet of Northern Gaul seemed to be based on a significant amount of a resource enriched in 13C likely millet or low trophic level marine resources unlike the southern population of Britain.