Orlistat also known as tetrahydrolipstatin, is a drug designed to treat obesity

Obesity

Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...

. Its primary function is preventing the absorption of fats from the human diet, thereby reducing caloric

Calorie

The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule...

 intake. It is intended for use in conjunction with a physician-supervised reduced-calorie diet

Dieting

Dieting is the practice of eating food in a regulated fashion to achieve or maintain a controlled weight. In most cases dieting is used in combination with physical exercise to lose weight in those who are overweight or obese. Some athletes, however, follow a diet to gain weight...

. Orlistat is the saturated

Saturation (chemistry)

In chemistry, saturation has six different meanings, all based on reaching a maximum capacity...

 derivative of lipstatin

Lipstatin

Lipstatin is a potent, irreversible inhibitor of pancreatic lipase. It is a natural product, and was first isolated from the Actinobacterium Streptomyces toxytricini....

, a potent natural

Natural product

A natural product is a chemical compound or substance produced by a living organism - found in nature that usually has a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design...

 inhibitor of pancreatic lipase

Pancreatic lipase

Pancreatic lipase, also known as pancreatic triacylglycerol lipase, is secreted from the pancreas, and is the primary lipase that hydrolyzes dietary fat molecules in the human digestive system, converting triglyceride substrates found in ingested oils to monoglycerides and free fatty acids.Bile...

s isolated from the bacterium

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 Streptomyces toxytricini

Streptomyces toxytricini

Streptomyces toxytricini is a Gram-positive bacterium belonging to the genus Streptomyces. It produces the pancreatic lipase inhibitor lipstatin, of which the antiobesity drug orlistat is a derivative....

. However, due to simplicity and stability, orlistat rather than lipstatin was developed into an anti-obesity drug.

The effectiveness of orlistat in promoting weight loss

Weight loss

Weight loss, in the context of medicine, health or physical fitness, is a reduction of the total body mass, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon and other connective tissue...

 is definite, though modest.