ENERGY-BALANCE AND THERMOGENESIS IN RATS CONSUMING NONSTARCH POLYSACCHARIDES OF VARIOUS FERMENTABILITIES

Background: The equivalents of dietary protein, fat, and available car bohydrate as fuels for maintenance (kJ apparent metabolizable energy/k J maintenance requirement) are known from classical experiments and ar e similar across species; that for nonstarch polysaccharide (NSP) is u ndetermined. Objectives: Our objectives were to determine the energy e quivalent of NSP and the thermic responses to NSP. Design: In a random ized block design, 120 rats were treated in groups of 10 for 28 d with a basal diet (control) supplemented with starch and 10 different NSP treatments in amounts between 38 and 92 g/kg basal diet. Cellulose and starch were references. Thermic responses, deduced from body-composit ion changes and modeling of energy disposition, and energy and substra te excretion were determined. Results: NSP had fermentabilities betwee n 0.01 and 0.93 gig intake. Fermentability, partial digestible energy, and net metabolizable energy values of NSP were closely related. Gene rally, 51% of apparent metabolizable energy from NSP (fermentable gros s energy) met maintenance requirements. Diet (energy)induced thermogen esis (DIT) was evident from whole diets. Fermentable NSP supplied net metabolizable energy and caused DIT. After DIT and fermentation were a ccounted for, NSP induced thermogenesis was generally -2 +/- 4% ((x) o ver bar +/- SEM) of gross NSP energy, except for an outlying pectic pr eparation, which was 33% (P < 0.1). Conclusions: The energy equivalent of NSP was 196 (100/51) kJ/kJ, compared with 128, 105, and 100 for pr otein, fat, and glucose, respectively, from the classical experiments. With the exception of pectic NSP, NSP does not induce thermogenesis i n excess of that associated with DIT and fermentation.