Food energy values of dietary fibre components and decreased deposition of body fat.

The effects of guar gum (GG) and solka floc cellulose (SF) on food intake, stomach emptying and body fat deposition in rats were assessed together with their food energy values. Voluntary food intake in meal-fed rats (ca 100 g, male Wistar kept at 21C) was depressed initially by 40 per cent on adding 10 g GG to 100 g fibre free (FF) semisynthetic diet. This effect was not sustained, intake doubling within 15 d. Similar effects were not observed with SF. In pair-fed animals neither GG nor SF affected the rate of stomach emptying after 28 days. Digestible energy (DE) intake per rat over the 28 days was GG diet = 4616, SF diet = 4410, FF diet = 4373 kJ but body fat was lower in GG (25%) and SF (16%) fed rats than in FF fed rats. The calculated DE values of the fibre components were 10.1 kJ/g GG and 1.5 kJ/g SF (sem 1 kJ/g). After including body fat into the equations for metabolizable energy, the energy values were -7.1 kJ/g GG and -4.8 kJ/g SF (sem 2 kJ/g). This is equivalent to an increased energy expenditure of 17.2 kJ/g GG and 6.3 kJ/g SF. For GG an increased intestinal mucosal mass and cell turnover explains part of the apparent increase in energy demand. Our overall conclusion is that under certain circumstances and with regard to fat deposition some fibre components can be attributed negative energy values.