The time spent in sedentary behaviour represents an important public health burden. Toreduce sedentary time in the general population, the simplest, most effective, and mostaccessible method is to decrease lying and sitting time. We aimed to compare differenceson energy expenditure (EE) across lying, sitting, and standing positions; and to analyse theassociations between the change on EE of changing from one position to another andanthropometric and body composition parameters in young healthy adults. A total of 55(69% women) young healthy adults aged 21.7 ± 2.2 participated in the study. We measuredEE by indirect calorimetry across lying, sitting, and standing positions following the standardprocedures. The EE was significantly higher in standing than in both lying and sitting positions(mean difference: 0.121±0.292 and 0.125±0.241 kcal/min, respectively; all P<0.001),and no differences were observed between lying and sitting positions (P = 1.000). Therewas a negative association between the EE differences in sitting vs. standing position andlean body mass (P = 0.048), yet no associations between EE differences with the rest of theanthropometric and body composition parameters were observed in each position pair studied(all P>0.321). Our findings support the fact that increasing the time spent standing couldbe a simple strategy to slightly increase EE. Therefore, our results have important clinicalimplications including a better monitoring, characterizing, and promoting countermeasuresto sedentariness through low-level physical activities.