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Energy expenditure (EE) may decrease in subjects on hypocaloric diets, in amounts that exceed body mass loss, favoring weight regain. Objective: to verify if a short-term caloric restriction lowers Resting Energy Expenditure (REE) and Total Energy Expenditure (TEE) more than predicted by changes in body composition, and if this reduction of EE is related with compliance to the diet. Methods: twenty-two women aged 23-44 years with a body mass index (BMI) of 25-32 kg/m², underwent a three-month calorie restriction treatment (20 kcal / kg initial weight) and were encouraged to increase their physical activity. At the beginning and end of the intervention, body composition (DEXA), REE, Physical Activity Energy Expenditure (PAEE) and TEE were assessed, through a combination of indirect calorimetry and actigraphy. Participants, who lost more or equal than 5% of their initial weight were considered compliant with the diet. Results: in the compliant group, REE decreased, when expressed in absolute numbers or when adjusted by fat free mass (FFM) [-164 ± 168 kcal/day (10,6%) and -4,3 ± 4,6 kcal/kg FFM (10,5%)]. This decline was significantly greater than that observed in the non-compliant group [-6,2 ± 1.42 Kcal/day (0.16%) and -0,5 ± 3,4/Kg FFM (0.96%)]. FFM did not change in any of the two groups. At baseline, there was a significant correlation between FFM and REE (r = 0, 56 p < 0,05), which was lost at the end of the intervention. Conclusions: compliant women showed a significant reduction in both absolute and adjusted REE, which together with the loss of correlation between REE and FFM at the end of the intervention suggests a metabolic adaptation. El gasto energetico (GE) puede disminuir en sujetos sometidos a dietas hipocaloricas, en una magnitud que excede la reduccion explicada por los cambios en la composicion corporal; dificultando la mantencion del peso perdido. Objetivo: verificar si el Gasto Energetico en Reposo (GER) y Total (GET) experimentan una disminucion mayor a lo atribuible a cambios en la composicion corporal y dependen de la adherencia al tratamiento dietario. Metodologia: veintidos mujeres (23-44 anos) con Indice de Masa Corporal (IMC) entre 25 y 32 kg/m² fueron sometidas a tres meses de restriccion calorica (20 kcal/kg de peso inicial) y motivadas a aumentar su actividad fisica. Al inicio y al final se evaluo: peso, masa grasa (MG) y masa libre de grasa (MLG) con DEXA, GER (calorimetria indirecta), Gasto Energetico por Actividad Fisica (GEAF) y GET (actigrafia). Las participantes que perdieron . 5% del peso inicial fueron consideradas como adherentes a la dieta. Resultados: el grupo adherente tuvo una disminucion significativa del GER absoluto [-164 �± 168 kcal/dia (10,6%) y -4,3 �± 4,6 kcal/kg MLG (10,5%)]. Esta disminucion fue significativamente mayor que la observada en el grupo no adherente [-6,2 ± 1.42 kcal/dia (0.16%) y -0,5 ± 3,4/kg FFM (0.96%)]. La MLG no cambio en ninguno de los dos grupos. Existio asociacion significativa entre MLG y GER (r = 0,56; p < 0,05) solo al inicio en el grupo total. Conclusiones: las mujeres adherentes a la restriccion calorica mostraron una reduccion en el GER tanto absoluto como ajustado por la MLG, lo cual, junto con la perdida de correlacion entre el GER y la MLG al final de la intervencion, sugieren adaptacion metabolica.

Energy expenditure (EE) may decrease in subjects on hypocaloric diets, in amounts that exceed body mass loss, favoring weight regain. Objective: to verify if a short-term caloric restriction lowers Resting Energy Expenditure (REE) and Total Energy Expenditure (TEE) more than predicted by changes in body composition, and if this reduction of EE is related with compliance to the diet. Methods: twenty-two women aged 23-44 years with a body mass index (BMI) of 25-32 kg/m², underwent a three-month calorie restriction treatment (20 kcal / kg initial weight) and were encouraged to increase their physical activity. At the beginning and end of the intervention, body composition (DEXA), REE, Physical Activity Energy Expenditure (PAEE) and TEE were assessed, through a combination of indirect calorimetry and actigraphy. Participants, who lost more or equal than 5% of their initial weight were considered compliant with the diet. Results: in the compliant group, REE decreased, when expressed in absolute numbers or when adjusted by fat free mass (FFM) [-164 ± 168 kcal/day (10,6%) and -4,3 ± 4,6 kcal/kg FFM (10,5%)]. This decline was significantly greater than that observed in the non-compliant group [-6,2 ± 1.42 Kcal/day (0.16%) and -0,5 ± 3,4/Kg FFM (0.96%)]. FFM did not change in any of the two groups. At baseline, there was a significant correlation between FFM and REE (r = 0, 56 p < 0,05), which was lost at the end of the intervention. Conclusions: compliant women showed a significant reduction in both absolute and adjusted REE, which together with the loss of correlation between REE and FFM at the end of the intervention suggests a metabolic adaptation.