Active Ingredients: Orlistat
Automated searches were supplemented by examination of expert recommendation reports and bibliographic references from included research studies, as well as searches for the names of medications approved by the FDA for weight loss treatment or known to be used off-label for weight loss.
Although the emphasis of this review is primarily on outcomes available from placebo-controlled, double-blind, randomized clinical trials, if other data were not available, we also present the results of open-label studies, as well as case series that report weight reduction as a primary or secondary endpoint of the study.
Open in a separate window aNote: ethanol extract. Dietary fats are absorbed in the intestine and they function as an energy supply, thermal regulators, membrane constituents, energy storage and some play an important role in body function as essential fatty acids and fat-soluble vitamins.
TG consist of a single molecule of glycerol, attached by ester bonds to three fatty acids. TG cannot be absorbed; therefore, intestinal enzymes must hydrolyze the ester bonds on the glycerol backbone in order for the molecule to be absorbed.
The products of this hydrolysis are mainly free fatty acids FFA and 2- monoglycerides 2-MG which can be absorbed by the duodenum.
In vivo TG hydrolysis is catalyzed by several digestive lipases. There are several human lipases which include the pre-duodenal lingual and human gastric lipase HGL and the extra-duodenal pancreatic, hepatic, lipoprotein and endothelial lipases.
The pancreas also secretes colipase, a factor that is necessary to optimize pancreatic lipase activity. Colipase binds to bile acid micelles and phospholipid-covered emulsions. Once bound to these surfaces, colipase facilitates the interaction between pancreatic lipase and the surface of emulsified lipid droplets.
The secretion of HGL is induced by mechanical stimulation of the stomach, ingestion of food or sympathetic activation. Colipase is secreted as a precursor molecule, in the presence of bile salts, pro-colipase binds, without inducing any conformational change, to the C-terminal domain of the HPL molecule.
These micelles transport these lipolytic products from the intestinal lumen to the intestinal walls. The enterocyte re-esterifies 2-MG and FFA into TG, assembles them into chylomicrons and then secretes these into the lymphatic system in order make them bioavailable.
According to their chemical structure carbohydrates can be classified into absorbable undigested, digestible, fermentable and non-fermentable forms.
However, once a carbohydrate comprises two or more units, it has to be enzymatically digested for it to be absorbed. In the human diet, the main digestible carbohydrates comprise disaccharides such as sucrose sugar and lactose, and larger polysaccharides such as starch which constitute a main source of calories in most Western diets.
In contrast, fermentable carbohydrates cannot be digested as enzymes cannot readily break the inter saccharide bonds.
However, once in the colon these carbohydrates are readily metabolized by colonic bacteria through the process of fermentation. Similarly, if digestible carbohydrates such as sucrose and lactose are maldigested or malabsorbed, they will also be fermented in the large intestine.
The main end products of carbohydrate fermentation are short-chain fatty acids acetate, propionate, and medicine and gases carbon dioxide, hydrogen, and methane.
They pass through the gastrointestinal GI tract mostly unchanged and are eliminated in the feces.
A small proportion of monosaccharides can be absorbed passively; however, a carrier protein is required to absorb the amount ingested in a normal diet.
This is mainly due to their high energy content and their low potential for inducing satiety. Given the central role of dietary fat in weight gain, a rational strategy would be to reduce the proportion of calories derived from fat in the diet.
In addition to altering dietary intake, the amount of fat entering the body can be reduced by targeting the enzymes involved in lipid digestion and absorption pathways.
As detailed later, GI distress and vitamin deficiencies remain a concern with current treatments.
However, humans can tolerate a certain degree of inhibition of fat absorption, sufficient to prevent a significant amount of energy entering the body.