Chitin is a cellulose-like biopolymer found mainly in the exoskeleton of marine animals such as shrimp, crabs, or lobsters. It is a fibrous substance that can block absorption of dietary fat and cholesterol. Shellfish like shrimp, lobster and crab, may seem an unlikely source of a natural remedy for weight loss. But, the outer shell of shellfish is composed of chitin, a naturally occurring compound that has been dubbed a ‘fat magnet’ by researchers. Chitosan's purported mechanism of action offers the dream of weight loss without dietary restrictions or lifestyle modifications (such as exercise). It also offers an alternative to ephedra- or other stimulant-based products, which are increasingly recognized as dangerous. Chitosan is safer and has less potential for abuse than some pharmaceutical agents, especially those with central-nervous-system effects, such as phentermine and sibutramine. Chitosan also appears safer than fenfluramine and dexfenfluramine, which have been removed from the market because of association with cardiac valve abnormalities.

Chitosan differs from many other weight-loss supplements in that it is not claimed to increase energy expenditures. It also differs from many current prescription drug treatments focused on inducing satiety. Chitosan is promoted as a product that binds to lipids in the gastrointestinal tract, decreasing their absorption and naturally lowering body weight. Research includes use as a soluble dietary fiber to treat obesity, high cholesterol, and Crohn’s disease. It is also used to treat complications with kidney failure patients, anemia, loss of strength and appetite, and insomnia. Chitosan is completely indigestible and is, in essence, similar to cellulose, or plant fibre. Just like fibre, but even more powerful, it binds to fat molecules in your bowel and prevents them from being absorbed by your body. Instead, it accompanies them through the bowel where they are eliminated in the stools. Chitosan can bind up to six times its weight in fat. The result is that you absorb less fat and therefore fewer calories, helping you to lose weight. With proper diet and exercise, chitosan is one of the best ways to naturally and effectively lose weight. 

Chitosan is a processed form of chitin with a number of commercial and biomedical uses. It can be used in agriculture as a seed treatment and biopesticide, helping plants to fight off fungal infections. Chitosan is as well used in medicine and dressings, being used in emergency rooms to control bleeding and as an antibacterial agent. Bandages impregnated with chitosan and chitosan granules have been approved by the FDA for use in emergency settings to control blood loss,while enhancing platelet activation, vasoconstriction, and ionic action on red blood cells

Chitosan's characteristic as a film-forming and protective polysaccharide suggests a potential role in wound healing and burn treatment. Topical application of chitosan granules controls bleeding in less than 3 minutes, where pressure alone failed. it can also be used to help deliver drugs through the skin. In an effort to help “donor tissue” rebuild itself, plastic surgeons sometimes apply chitosan directly to places from which they have taken tissue to be used elsewhere. Recent studies have shown chitosan also exerts action against candida and std's like chlamydia

it was found that chitosan reduces scar formation following injury and prevents adhesions (when your tissues become fused) after joint damage. Used in the long term, chitosan supplements maintain the health of the ligaments and generally improve mobility of the joints 

• In addition to the above, chitosan has other benefits:
• It is used as a bone growth factor, and also in creating artificial bone that can be used to treat fractures
• As a food preservative, it inhibits the growth of bacteria. Studies show that chitosan weakens the outer shell of bacteria such as E.Coli and salmonella, and so it destroys the bacteria causing food poisoning 
• As a biological component of capsules, it allows the capsule to dissolve easily in the stomach and so it makes drug delivery much more effective
• As a wound dressing, Chitosan helps wounds heal fast and, at the same time helps reduce the likelihood of infection
• Chitosan has a chemical structure somewhat similar to that of glucosamine, a well-known natural treatment for arthritis. This means that it behaves the same way as glucosamine with regards to tissue healing.
• A very recent experiment showed that chitosan helps prevent diabetes in mice, particularly the form of diabetes that is related to obesity. This experiment showed that chitosan decreases blood sugar, and that the more chitosan is used, the more the blood sugar is lowered. In addition, other studies have found that chitosan balances the actions of the cells that produce insulin, and so makes insulin work more efficiently in reducing blood sugar 
• Avoid supplementation with chitosan if you are pregnant or if you are allergic to shellfish.