Many persons in the United States consider themselves overweight. That self-perception may be more prevalent than obesity itself, but even so, by medical standards a good 33% to 50% of Americans are overweight.8 That condition can aggravate or even cause serious physical afflictions such as diabetes, high blood pressure, and heart disease. Persons seeking slimness and who are dissatisfied with results from changes in diet and exercise may seek pharmacological help.
The first diet drug to receive scientific endorsement was thyroid hormone. Its use for this purpose began in the 1890s on the theory that it would boost a person’s metabolism and thereby promote faster use of calories. The same theory made dinitrophenol a standard diet drug before World War II. Although it boosted metabolic rate, it also boosted rates of cataracts and of harm to the peripheral nervous system (which involves the functioning of various organs and muscles). For those reasons the drug was abandoned. In the 1930s amphetamines became available and quickly became a popular diet aid despite their potential for abuse.
Many stimulants suppress appetite, and some are used as medicines to help people lose weight. Those medicines are called “anorectics.” Their stimulant effects may be lower than drugs in other classes but can still have potential for abuse and addiction. For that reason, many anorectics are scheduled substances.
Such drugs are casually described as appetite suppressants, but not all promote weight loss in that way. For instance, some may affect the way food is absorbed in the body; some increase a person’s rate of metabolism so the person burns more calories; some make a person more physically energetic. Question has even been raised about whether a stimulant’s anorectic action simply comes from elevating the mood of depressed people and thereby reducing their need to gain comfort from eating. Mechanisms by which anorectics work are poorly understood.
Indeed, whether they work at all is uncertain. Compared to placebos, most studies show additional weight loss among persons taking anorectics to be measurable but barely noticeable; some studies show anorectics to be no more effective than placebos. In experiments where anorectics work well, skeptics wonder if results come from factors other than the drug, such as rapport between physician and patient, belief that the substance would work, or even from basics such as controls on food intake during the experiment. Scientists directing one study of anorectics concluded that sensations of appetite suppression were so subtle that a user could miss them unless the person was trying to be aware of them.
The effectiveness of an anorectic declines as weeks go by, through development of tolerance. A telling exception to development of tolerance is methylcellulose, an unscheduled substance used to increase bulk of consumed food and thereby increase the physical feeling of fullness. The substance has no psychological effect, and no tolerance develops. Methylcellulose is also among the least effective dieting aids.
Abusers of stimulant anorectics exhibit symptoms similar to those found among abusers of amphetamines, from skin rash to psychosis. Some persons using anorectics properly under medical supervision experience muscle pain and cramps, weariness, peevishness, depression, difficulty in thinking. That group of symptoms is the same as those undergone by persons trying to cope with lack of food regardless of drug use, a coincidence raising question about whether some undesired effects attributed to anorectics are simply undesired effects of being hungry.
A harsh fact about anorectics is that weight lost while using them tends to return if a person stops taking the drugs (and generally they are intended for short-term use only). Behavioral therapy teaches people how to change their eating and exercise habits. A comparison study not only found behavioral therapy superior to anorectic therapy in preventing regain of lost pounds but also found behavioral therapy to be more effective alone than when using anorectics along with it—a troubling result for advocates of anorectics. Skeptics ask whether drugs that produce only mild temporary improvement in a chronic condition are worth anything.
For information about specific anorectic class stimulants, see alphabetical listings for: benzphetamine, diethylpropion, fenfluramine, mazindol, phendimetrazine, phenmetrazine, phentermine, and sibutramine