Highly branched .alpha.-glucan having an average molar weight of at least 10.sup.5 Da can be used for inducing or enhancing satiety and/or satiation in humans or animals by incorporation of the .alpha.-glucan into a liquid nutritional or pharmaceutical composition, preferably together with a food protein. The .alpha.-glucan induces a viscosity increase upon lowering the pH. The degree of branching of the .alpha.-glucan is at least 8%. Such .alpha.-glucans can be obtained e.g. by fermentation of lactobacillus strains having glucosyltransferase activity on a sucrose substrate.