Objective: Higher levels of physical activity have been associated with body weight maintenance, but previous work in our laboratory suggests that this is not purely related to energy balance. We hypothesize that this may be related to the partitioning of dietary fat between oxidation and storage.
Research methods and procedures: Healthy women (age 24 +/- 1 years, BMI = 21.2 +/- 0.4 kg/m2) were recruited to participate in rest (n = 10) or exercise sessions of light (n = 11), moderate (n = 10), and heavy (n = 7) exercise. All exercises (1250 kJ above rest) were performed on a stationary cycle inside of a whole-body calorimeter. [1-(13)C]oleate and [d31]palmitate were given in a liquid meal 30 minutes post-exercise. An additional study was done with identical exercise sessions, but with administration of an oral dose of [1-(13)C]acetate and [d3]acetate 30 minutes post-exercise to determine label sequestration.
Results: Cumulative oxidation of [1-(13)C]oleate was significantly greater after light (45 +/- 3%), moderate (54 +/- 4%), and heavy (51 +/- 4%) exercise than that with rest (33 +/- 3%) (p = 0.0008). Cumulative oxidation of [d31]palmitate did not differ among trials (12 +/- 2%, 14 +/- 1%, 17 +/- 2%, and 14 +/- 2% for rest, light, moderate, and heavy, respectively; p = 0.30).
Discussion: Exercise standardized for energy expenditure increases monounsaturated fat oxidation more than saturated fat oxidation and that the increase occurs regardless of intensity. Recommendations for physical activity for the purposes of weight control may be specific for dietary fat composition.