The primary objective of the proposed study is to demonstrate the feasibility of measuring nocturnal whole-body and regional lipolysis by using stable isotope techniques and microdialysis of subcutaneous abdominal adipose tissue respectively with the long term goal of determining the effects of acute exercise during the daytime on rates of lipolysis at night in men and women. A secondary objective of this study is to determine if nocturnal regional lipolysis measured by microdialysis of subcutaneous abdominal adipose tissue and whole body lipolysis measured by a stable glycerol isotope infusion are related to dietary and whole body fat oxidation measured by stable isotope labelled fatty acid and whole-room calorimetry, respectively. Finally, the study aims to determine if sleep quality parameters measured by EEG and wrist actigraphy correlate with measures of nocturnal fat oxidation and lipolysis (regional and whole body)