The gene links nutrient absorption and metabolism to the circadian clock. Shift workers are at a heightened risk of overweight and of developing obesity and metabolic syndrome. This study investigates the diurnal variation of in healthy volunteers and its expression levels in rotational shift and daytime workers. expression levels were evaluated in peripheral blood lymphocytes from 15 healthy volunteers at 4-hour intervals for 24 h. Metabolic parameters and expression were measured in workers engaged in shift and daytime work.In the group of volunteers expression showed diurnal variation, with a peak at 8:00 AM. expression was higher in shift workers than in daytime workers. Multivariate analysis confirmed the role of shift work as an independent factor affecting expression. Notably, its level correlated directly with body mass index and inversely with total energy expenditure.Measuring expression levels in human peripheral blood lymphocytes can improve investigations on the relationship between changes in circadian rhythm and metabolic disorders. Shift workers show higher levels than daytime workers.