Several prescription medications are currently approved for treatment of obesity. In general, the effects of these medications are modest, leading to an average initial weight loss of between 5 and 22 pounds; though studies show that weight returns after cessation of the drugs. There is considerable individual difference in response to these medications; some people experience greater weight loss than others.
Short-term use of appetite suppressant medications has been shown to modestly reduce health risks for obese individuals. Studies have found that these medications can lower blood pressure, blood cholesterol, blood fats (triglycerides) and decrease insulin resistance (the body's inability to utilize blood sugar). Long-term studies need to be conducted to determine if weight loss assisted by appetite suppressant medications can improve health long-term.
Weight loss tends to be greatest during the first few weeks or months of treatment, leveling off after about six months. Research suggests that if a patient does not lose at least four pounds during the first four weeks on a particular medication, that medication is unlikely to be effective over the long run.
Short-term use (few weeks to few months): Examples include diethylpropion (Tenuate®), and phentermine (Adipex-P®).
The mechanism of action of diethylpropion and phentermine appears to be secondary to CNS (central nervous system) effects, specifically stimulation of the hypothalamus to release catecholamines into the central nervous system. Appetite-suppressing effects are mediated via norepinephrine and dopamine metabolism.
Long-term use (up to one year or more): Examples include orlistat (Xenical®) and sibutramine (Meridia®).
Orlistat is the first prescription treatment for obesity that does not act as an appetite suppressant. It works by interfering with the action of gastrointestinal (GI) lipase in the GI tract. As a result of this mechanism of action, 30% of ingested dietary fat is not absorbed.
Sibutramine and its two primary metabolites also appear to be secondary to CNS effects by blocking the neuronal uptake of norepinephrine, serotonin and dopamine.
OTC (over-the-counter): It is believed that the "P57" molecule in hoodia mimics the effect of glucose has on the brain, telling part of the brain (the hypothalamus) that the person feels full. Consequently, the person has no desire to eat. However current available evidence on hoodia's effectiveness and safety is lacking.
Dietrine Carb Blocker with Phase 2®: An ingredient extracted from white kidney beans is thought to neutralize the digestive enzyme alpha amylase before it can convert starch into glucose and then fat.