Do dietary supplements for weight loss work?

Abstract

also reduce caloric intake, food ingestion rate, and nutrient absorption due to its soluble fi ber backbone. Glucomannan’s effect on satiety is the result of its fi ber content; it was associated with a modest weight loss of 5 pounds in 8 weeks, according to a November 2005 study published in Alternative Therapies in Health and Medicine (http:// apha.us/ZVeaAG). A slight decrease in total cholesterol and triglyceride concentrations may occur with the use of glucomannan, although similar results may be obtained with a high-fi ber diet. Sensa is another popular weight loss product heavily promoted to consumers. Invented by neurologist Alan Hirsch, the product is based on the central mechanisms that regulate satiety. Sensa’s manufacturers claim that when it is sprinkled on food, it enhances the smell and taste of the food and, as a result, the feeling of satiety. There has been no evidence documenting the effi cacy of Sensa for signifi cant weight loss or maintenance of weight loss published in peer-reviewed journals, however. White kidney bean (Phaseolus vulgaris) extract (WKBE) acts as an inhibitor of alpha amylase, resulting in decreased digestion and intestinal absorption of carbohydrates. In Diabetes, Metabolic Syndrome, and Obesity: Targets and Therapy, researchers reported a reduction in postprandial blood glucose with WKBE, which may be helpful for patients with type 2 diabetes (http:// apha.us/15i8baA). The best results occurred when WKBE was taken with meals containing large amounts of carbohydrates. The product may delay gastric emptying, thus simulating the feeling of satiety, and resulting in weight loss. WKBE should not contain phytohemagglutinin, a toxic protein found in P. vulgaris. Products should have a hemagglutinating activity less than 700 units/g and trypsin inhibiting activity less than 20 units/g (dry weight), according to a review published in Nutrition Journal (http://apha.us/ZNt3DC). Raspberry ketone, present in raspberries, cranberries, and blackberries, has a structure similar to capsaicin and synephrine. Researchers have theorized that capsaicin enhances thermogenesis, resulting in increased energy expenditure. There are limited data on the safety and effi cacy of synephrine, an alpha-adrenergic agonist, as an alternative to ephedra, and it may increase blood pressure. In a 2010 study published in Planta Medica, raspberry ketone, when fed to male mice in high dosages, prevented high-fat diet–induced increase in weight, stimulated lipolysis in white adipocytes, and increased expression of adiponectin. Bitter orange, Citrus aurantium, has been proposed to work similarly to raspberry ketone because it includes synephrine, N-methyltyramine, and furocoumarins. The product is believed to increase metabolism and suppress appetite, but evidence on its safety and effi cacy is limited. Fainting, heart attacks, and strokes in otherwise healthy people have been reported with bitter orange alone or in combination with caffeine.