In recent years, a bypass surgery by which the upper part of the stomach is directly connected to the lower part of the small intestine in a surgical manner has been deemed to be effective in treating diabetes (especially type 2 diabetes) and obesity. In a state where such a bypass surgery is performed, since the ingested nutrients directly flow into the lower part of the small intestine from the upper part of the stomach, nutrients do not flow to the duodenum and the upper part of the jejunum which are the upper parts of the small intestine. As a result, it is possible to reduce the absorption of nutrients. Since nutrients do not flow to the upper part of the small intestine, glucose-dependent insulinotropic polypeptide (GIP), glucagon, and the like that are gastrointestinal hormones which are secreted due to a stimulus by nutrients are less likely to be secreted. In addition, when undigested nutrients pass through the lower part of the jejunum and the ileum which are the lower parts of the small intestine, glucagon-like peptide-1 (GLP-1) which is a gastrointestinal hormone is increasingly secreted due to stimulus by nutrients. GIP and glucagon are deemed to be factors which reduce the amount of secretion of insulin, and since GIP and glucagon are not secreted, the secretion of insulin is less likely to be inhibited. In addition, GLP-1 is deemed to be a factor which stimulates the secretion of insulin. As described above, the absorption of ingested nutrients is not only restricted, but the secretion of insulin is also stimulated due to the action of gastrointestinal hormones, and the blood glucose level is reduced, and thus the bypass surgery is deemed to be effective in the treatment of diabetes and obesity.
However, the bypass surgery is highly invasive, and thus in recent years, health professionals have given attention to a low-invasive method by which a sleeve allowing the flow of nutrients therethrough is placed on the upper part of the small intestine. For example, U.S. Pat. No. 7,803,1951 discloses a device including two balloons which are disposed with the pyloric ring of the stomach interposed between the two balloons, and a tubular sleeve which extends from the balloons toward the small intestine. U.S. Patent Application Publication No. US2010/0305590 discloses a device in which a projected anchor which is hooked onto the pyloric ring of the stomach is adopted instead of the balloons.