Short-term experiments in rats using indirect calorimetry are a suitable method for comparative estimation of the energetic availability of dietary fibres. Results are partly in agreement with values estimated by long-term in vivo methods.

The action of sucrose polyesters (SPE) as undigestible fat-like compounds on lipid metabolism of growing rats was studied. Over a period of 4 weeks the animals were fed a semi-synthetic diet containing 6 % of SPE with or without reduction of dietary fat. The substitution of dietary fats by SPE or the additional supply of SPE led to an increase of fecal lipid and cholesterol excretion, which was accompanied by a significant stimulation of in vitro cholesterol synthesis of the liver and by a significant reduction of liver cholesterol. The serum cholesterol level, however, was not affected, whereas the level of triglycerides both in serum and liver was significantly reduced to about 40% of that found in control animals.

Academy of Sciences of the GDR Accumulaticn of sucrose polyesters in different organ lipids of rats (&or t communication) L. Aust, J. Briickner, R. NoackandG. Mieth Esters of sucrose and long chain fatty acids with 6 and more acyl grwp (polyesters -SPE) are a s undigestible and unabsorbable fat-like compounds of interest a s a fat substitute in dietary food-stuffs for reductirn of energy intake. Furthermore, due to their

Short communication) L. AUST, R. NOACK and J. PROLLOvernutrition in rodents during early postnatal life induced by breeding in small nest sizes leads to distinct metabolic changes, which remain throughout life even under conditions of free access to normal food. An accelerated body fat accumulation and a probably higher efficiency of energy utilization render this animal model suitable for the study of relations between the development of an obese state and its metabolic causes [ 1, 21. There is increasing evidence from studies in human beings [3,4] as well as in rodents [S, 61 that a higher body fat content is associated with a lower thermogenic response to food ingestion, assumed to indicate an increased efficiency of energy utilization. First results concerning postprandial thermogenesis in postnatally overfed rats are presented here.The experiment was carried out with male rats of the Wistar strain (Wist Schoe, VEB Versuchstierproduktion, Schonwalde near Berlin, GDR), which were grouped immediately after birth in nests of 2 or 12 animals. After weaning (4 weeks) the animals were kept in single cages and fed ad libitum with standard pellets (type R, VEB Versuchstierproduktion). At an age of 7-9 weeks the energy expenditure ofthe rats was determined by indirect ca!orimetry in an open system. For this purpose the animals were transferred into metabolic cages (Simax, CSSR), supplied with a constant stream of fresh air (80 I/h, (25 f 1) "C, 100% relative humidity). Oxygen consumption and carbon dioxide production were estimated paramzgnetically and by infrared absorption using Permolyt 2 and Infralyt 4 (VEB Junkalor, Dessau, GDR), respectively. To compare energy intake the rats got at 8 a.m. a semisynthetic diet (casein 15%, wheat starch 53 %, sucrose lo%, sunflower oil 15 %, cellulose 2 %, salt mixture 4 %, vitamine mixture 1 %) limited to 500 kJ metabolizable energy per kg0.75.

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