Increasing fat content in an isocaloric diet is associated with positive fat imbalance. Exercise attenuates this process, and the authors hypothesized the attenuation was a result of altered postprandial lipid trafficking.
To investigate the effects of prior exercise and nutritional state on the metabolic fate of dietary fat, a study was designed with 4 treatment arms. Energy-balance modifications (fed or fasted) ± exercise were followed by postexercise feeding of 1-14C oleic acid to Sprague-Dawley rats. Fed rats were fed 6 hr before treatment, whereas fasted rats were fasted for 15 hr before treatment with the primary variable being exercise.
14C content of gastrointestinal tract, plasma, breath, muscle (soleus, vastus lateralis [VL], and extensor digitorum longus), liver, and adipose tissue (retroperitoneal and epididymal) was measured at 5 time points postdose (1, 2, 4, 8, and 24 hr).
Compared with matched unexercised controls, fed rats undergoing acute exercise significantly increased recovery of 14C in breath (p = .005) and plasma (p = .001), and trends of increasing 14C recovery occurred in VL (p = .07) and soleus (p = .06). Acute exercise significantly increased recovery of 14C in breath (p = .003), VL (p = .04), and soleus (p = .03) in the fasted study. Acute exercise significantly decreased the trafficking of dietary tracer into adipose tissue in only the fed study (p < .0001).
Although the effect of acute exercise on trafficking dietary fat away from adipose tissue was greater in the fed group than in the fasted, acute exercise had beneficial effects on adipose tissue’s collecting dietary fat when fed or fasted.
Hansen is with the School of Medicine, University of Colorado Denver, Denver, CO. Schoeller is with the Dept of Nutritional Sciences, University of Wisconsin Madison, Madison, WI.