Diet Pills 101

Prescription weight-loss medications, also known as “diet pills” or “anti-obesity drugs” are medications that can help you lose weight in conjunction with a diet and exercise regimen. In addition to prescription medications, the market is flooded with weight-loss supplements, which are unregulated and sold over-the-counter.

As the number of overweight Americans increases, the number of diet plans, exercise plans, medications, and supplements has exploded. Weight loss can be achieved solely through diet and exercise, but weight-loss medications can help.

Weight-loss medications can provide benefits as well as side effects, and you should discuss their use (whether prescription or over-the-counter) with your doctor to make sure that you are not risking any harmful drug interactions with the other medications that you take, that you do not have any medical conditions that might worsen with a drug’s use, and that you are not allergic to any of the medications that you might take.

Benefits of weight loss

There is much evidence that a 5 to 10 percent weight-loss can improve many medical conditions. These include:

  • Lowering cholesterol: Losing weight helps to decrease “bad” cholesterol (LDL) and triglycerides while raising “good” cholesterol (HDL). All of these can help reduce heart disease and lower your risk of heart attack and stroke.
  • Hypertension: High blood pressure usually decreases with weight-loss. In fact, at least a quarter of all hypertension is caused by excess body weight.
  • Diabetes: Losing weight is a great way to lower Hemoglobin A1C, one of the markers used to screen for diabetes. Losing 5 to 10 percent of your body weight has been demonstrated to lower A1C as much as some antidiabetic medications!
  • Insulin Resistance: Insulin is a hormone produced by the pancreas that regulates blood sugar levels in the body. Overweight people often produce too much insulin, because their tissues are resistant to the hormone. Excess insulin can cause an increase in fat tissue in the waist area and can also cause abnormal cholesterol levels and hormonal changes in some women, causing male pattern hair growth.
  • Obstructive sleep apnea: Obstructive sleep apnea is a sleep disorder that is characterized by irregular breathing during sleep. This results in poor sleep and fatigue while awake. It can also make treatment of certain medical conditions (such as hypertension) more resistant to treatment. A modest loss of weight can cure obstructive sleep apnea, or at least make it less severe.
  • Inflammation: Fat cells in the body produce a number of inflammatory substances. Elevated levels of these substances can cause clots and plaques in the blood, increasing the risk of heart attack and stroke. A 10 percent weight reduction lowers the levels of these inflammatory substances and lowers the risk of vascular damage, heart attack, and stroke.

Weight-loss strategies

Currently, in the United States, the normal paradigm for weight-loss is diet and exercise with the occasional use of prescription medications. For many people, this regimen works well. For others, it does not. One of the reasons is that as we lose weight, our metabolism changes. When we eat fewer calories, we may lose some weight initially, but with lower calorie consumption, our metabolism slows. If caloric intake is not reduced, then weight-loss ceases.

Much of the medical establishment, including the American Medical Association, The American Society of Bariatric Physicians, and the North American Association for the Study of Obesity (as well as the Internal Revenue Service, strangely) consider obesity to be a chronic (and easily diagnosable) disease, and may consider long-term pharmacotherapy to control the disease. With this view, not only does weight loss need to be achieved, but once the weight is lost, the weight loss must be maintained.

Who is a candidate for weight-loss medications

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If you are trying to lose weight, diet and exercise alone should be your first attempt. If this fails, a discussion with your doctor about adding a weight-loss drug is recommended.


Prescription weight-loss medications are usually prescribed for people who have been unable to lose weight through diet and exercise and who have health related issues that are co-morbid with obesity. They are generally not prescribed for patients who want to lose a little weight for cosmetic reasons and are never prescribed for pregnant women.

The guidelines for the prescription of these drugs is that a patient must have a BMI (body mass index) of greater than 30, or a BMI greater than 27 along with a serious weight-related health issue such as hypertension or diabetes.

Another factor to take into consideration is cost. Not all health insurance/prescription plans cover weight-loss medications, and as with any prescription drug, they can be quite expensive.

Prescription weight-loss drugs should be used in conjunction with a diet and exercise regimen, and should not be used by pregnant women, even those who are overweight at the time of conception.

A vicious cycle

Being overweight often causes (or exacerbates) several medical conditions such as heart disease, high blood pressure, and diabetes. Many of the medications used to treat these and other medical conditions are shown to promote weight gain. These medications include:

  • Antidepressants: Many antidepressants have been demonstrated to stimulate the hunger center of the brain, making patients feel hungry and eat to excess.
  • Steroids: Often used to treat lupus and asthma, steroids can slow down metabolism and lead to lipogenesis – the creation of new fat cells. These drugs should be used on a short-term basis.
  • Beta blockers: This class of drugs can cause a decrease in energy levels and limit the amount of physical activity patients can perform.
  • Insulin: Used to treat diabetes, insulin increases hunger and weight gain in diabetics, which can increase the need for more insulin to balance blood sugar levels, which can lead to further weight gain, etc…
  • Antibiotics: These drugs can also lead to weight gain with prolonged use. The farming industry has witnessed this effect for decades – animals on long-term antibiotics always gain weight. This could be due to the changes that antibiotics make to the makeup of good bacteria that live in our intestinal tract.

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If you are overweight and your doctor wants to prescribe a new medication, you should ask if the medication will make you gain weight, if there is a similar medication that is “weight-neutral” (it will neither make you gain nor lose weight), and what the duration of treatment with the new drug will be.


How weight-loss medications work

Weight loss pills work by several different mechanisms. These include:

  • Appetite Suppression: Certain substances contain appetite suppressing compounds. These act on the part of the brain that controls appetite, and are often stimulants such as caffeine and Hoodia. In addition to appetite suppression, stimulants also give you more energy to help make you more active, and thus burn more calories.
  • Diuretic Effects: Water is heavy, and our bodies contain a lot of it. Diuretic medications (often known as “water pills”) act by increasing urination and lowering the amount of water that our bodies hold. This weight is easy to gain back (by simply drinking fluids), and these medications can cause dehydration.
  • Decreased Lipogenesis: There are some medications that slow the action of lipogenesis, or the creation of new fat cells in the body.
  • Increased Resting Energy Expenditure: Some medications may help increase your metabolism to the point that you will burn more energy when you are resting.


Common weight-loss drugs:

There are a number of weight-loss drugs currently approved by the FDA and available by prescription. Some of the more common ones are:

  • Didrex: Works by decreasing appetite and increasing feelings of satiation. It may increase blood pressure and heart rate, cause insomnia, nervousness, constipation and dry mouth.
  • Tenuate: Works by decreasing appetite and increasing feelings of satiation. Side effects may include headache, increased blood pressure and heart rate, insomnia, constipation, dry mouth, and nervousness.
  • Belviq: Works by decreasing appetite and increasing feelings of satiation. May cause headache, dry mouth, nausea, fatigue, constipation, and dizziness.
  • Contrave: Works by decreasing appetite and increasing feelings of satiation. Side effects may include nausea, constipation, vomiting, headache, and dizziness.
  • Phendimetrazine: Works by decreasing appetite and increasing feelings of satiation. May cause increased heart rate and blood pressure, constipation, insomnia, dry mouth, and nervousness.
  • Adipex-P, Suprenza: Works by decreasing appetite and increasing feelings of satiation. May cause headache, increased heart rate and blood pressure, dry mouth, constipation, and nervousness.
  • Xenical: Works by blocking absorption of fat. Side effects may include decreased absorption of fat-soluble vitamins, intestinal cramps, gas with discharge, oily spotting (also known as anal leakage), diarrhea, incontinence, and fecal urgency.
  • Qsymia: Works by decreasing appetite and increasing feelings of satiation. Side effects may cause insomnia, dizziness, constipation, dry mouth, changes in sense of smell or taste, pins and needles sensation.
  • Saxenda: Works by slowing gastric emptying and increasing feelings of satiation. May cause nausea, vomiting, and pancreatitis.

How effective are weight-loss drugs?

Weight-loss drugs may not work for every patient, and as with all medications, a drug that works for one patient may not work for another. On average, prescription weight-loss drugs result in a 5 to 10-pound loss during the period of one year. This is when they are used in conjunction with a diet and exercise plan.

For example, a patient weighing 200 pounds can expect to lose 10 to 20 pounds in a twelve-month period. This is considered to be a safe rate at which to lose weight, and although it may seem like a small amount of weight lost, it may be enough to have positive effects on blood sugar levels as well as blood pressure and cholesterol.


How safe are weight-loss drugs?

Many weight-loss drugs are classified as controlled substances because they can become addictive. These include Tenudate, Didrex, Adipex-P, and phendimetrazine. They are usually prescribed for less than 3 months. Because of their side effects, they are not recommended if you suffer from hyperthyroidism, hypertension, or heart disease.

Many other weight-loss medications are approved for long-term use, but as with any drugs, there may be side effects, some of which are minor, others more serious. As with any drug, you should discuss potential risks of taking any medications with your doctor or pharmacist.


The Fen-Phen disaster

When diet pills are mentioned, many people think of fen-phen due to the enormous news coverage when it was discovered in the late 1990s that the drug caused often fatal heart valve injuries in patients who took the drug.

The combination of the two drugs fenfluramine and phentermine (commonly known as fen-phen) was an anti-obesity drug that used two anorectic drugs. The medication acts to release serotonin and norepinephrine, which acted to reduce feelings of hunger in the patients that took the drug. The problem was that it caused potentially fatal heart valve problems and pulmonary hypertension.

The FDA withdrew the drug from the market, the company that produced the drug (American Home Products, now known as Wyeth) has paid out over $13 billion in damages and is involved in continuing litigation with parties injured by the drug.


Weight-loss supplements

OTC (over-the-counter) dietary weight loss supplements exist in the hundreds. Consumers should be wary of any product that bears the labeling “This product has not been evaluated by the Federal Drug Administration (FDA). This product is not to be used to diagnose, treat, prevent or cure any disease.” In addition (and this is the frightening part), dietary supplements do not need to prove that they are effective. Or safe. When they are evaluated, they are usually found to be totally ineffective, if not downright dangerous.

If you do choose to take any of these supplements (and before you start taking them), confirm with your doctor or pharmacist that there are no potentially dangerous drug interactions with any other medications or supplements that you currently take.



While it was once thought that if you were overweight, you should simply limit the amount of food that you ate and do some exercise, that is no longer the case. Obesity has been recognized as a disease, and more importantly as a disease that is co-morbid with several other diseases. It is critical to our health to manage obesity, and prescription drugs can play a major part in managing our weight and keeping us healthy.

One thing is certain, though. There is no miracle pill that you can take to lose weight, and any prescription weight-loss medications need to be taken as part of a weight-loss strategy that includes diet and exercise.