A composition containing a swelling agent is provided, which less burdens the stomach and intestine even after excessive intake. A food, anti-obesity agent and constipation alleviator each containing the composition is also provided. [Means for Solution] A composition comprises a swelling agent composed of a water-soluble polysaccharide swellable in Japanese Pharmacopoeia first fluid or Japanese Pharmacopoeia second fluid and water; and a swell inhibitor operative to control the swell of the swelling agent. The swelling agent and the swell inhibitor are mixed in the state of solution, unified and then dried.