The present invention relates to polymer comprising a polysaccharide crosslinked with a spacer crosslinker, wherein the spacer crosslinker comprises a first optionally substituted aliphatic moiety terminated at each end with a second moiety comprising at least two carboxylic acid groups. The present invention also relates to a hydrogel, a method of forming the polymer or hydrogel, a composition and capsule comprising the polymer or hydrogel and a method treating obesity, pre-diabetes, diabetes, non-alcoholic fatty liver disease or chronic idiopathic constipation or of reducing caloric intake or improving glycemic control using the polymer or hydrogel and a method of weight-loss or improving the body appearance in a healthy subject. In a preferred embodiment, a space crosslinker (PEG-CA) formed by esterifcation between polyethylene glycol and citric acid is used to prepare a crosslinked carboxymethylcellulose (CMC) hydrogel.