An orally administrable implement for expanding in a stomach of an animal, including a mammal, to fill a space in the stomach, is provided for weight control. The implement includes: a fluid-permeable expandable container having a first dimension and a second dimension; and a plurality of clusters comprising a swellable material contained within the container and capable of swelling when contacted with a fluid; whereby when the implement is ingested, the fluid in the stomach enters the container causing the clusters therein to swell and the container to expand from the first dimension to the second dimension.