Dangers of Diet Pills

Diet Pills

For decades, dieters have hoped for a pill that can help them lose weight without side effects. Diet pills typically fall into two categories: over-the-counter and herbal remedies that are not regulated by the FDA, and prescription diet pills that have FDA approval. While some diet pills can help you lose weight, there can be some very real dangers associated with them.


Over-the-counter diet pills can be purchased without a prescription. While some have FDA approval, such as the over-the-counter strength orlistat known as Alli, others are supplements that are not regulated by the FDA.

The different pills have their own dangers and side effects, which should be considered when deciding whether diet pills are right for you. According to WebMD, the FDA has performed limited testing on many of these types of supplements over the years and discovered an array of ingredients not listed on the label, including controlled substances, drugs not allowed in the United States, and prescription medications. The FDA maintains a web page to warn consumers of tainted diet products that may have harmful ingredients.

Raspberry Ketone

Marketing for this product claims raspberry ketone regulates a hormone present in lower concentrations in people with obesity. The FDA has not evaluated the claims associated with raspberry ketone, nor has it approved this supplement as a weight loss medication.

According to celebrity nutritionist Kimberly Snyder, raspberry ketones may have some very real dangers associated with them, including:

  • The pills can cause a spike in body temperature, and may also cause a rise in blood pressure and heart rate.
  • No human studies exist showing the safety of raspberry ketones.
  • The pills may irritate certain conditions, such as COPD, asthma, and diabetes.
  • Because of lack of FDA approval, potential drug interactions and contraindications remain unknown.

WebMD also states that the chemical makeup of raspberry ketones resembles other stimulants, which suggests the potential for side effects associated with stimulants.

Thermogenic Fat Burners

A number of companies offer diet supplements that supposedly raise your body's metabolism and stimulate fat burning. Many of these pills have come and gone over the years, and several (such as ephedra) have been yanked from the marketplace due to the dangers associated with them.

Companies continue to release fat burner pills, however, which are often a combination of ingredients believed to raise the metabolism. Unfortunately, the main problem with all of these pills is lack of FDA regulation. While manufactures do list ingredients on the packaging, the FDA does not test the ingredients or their effects. Side effects and dangers of thermogenic fat burners include:

  • Liver damage: In 2009, the FDA issued a recall of the popular thermogenic fat burner Hydroxycut from the shelves because it caused liver damage ranging from jaundice to liver failure.
  • Anxiety, elevated heart rate and insomnia: Many thermogenics contain stimulants, which can cause a host of problems ranging from elevated heart rate to ongoing anxiety, according to noted physician Andrew Weil, M.D.
  • Addiction: Dr. Weil also cautions that many of the stimulants found in thermogenic fat burners are physically addictive. If you stop taking them, withdrawal may result.


Glucomannan is a type of soluble fiber that expands in your intestines, making you feel full. It also slows digestion, allowing you to feel full longer, and slows the absorption of glucose, keeping blood sugar steadier. A number of over-the-counter diet pills contain this ingredient.

WebMD lists two primary concerns with glucomannan:

  • Taking it without sufficient water can lead to choking or blockages of the intestines, throat, and esophagus, according to a meta-analysis study in the American Journal of Clinical Nutrition.


Unlike the other over-the-counter weight loss supplements listed above, orlistat is actually approved by the FDA for over-the-counter sale to induce weight loss. Orlistat is marketed in non-prescription strength as Alli. It is also marketed in prescription strength as Xenical.

Orlistat blocks the absorption of some of the fats from the foods you eat. While orlistat is generally recognized as safe, the package insert lists a number of unpleasant "treatment effects" including oily anal discharge, loose stools, painful bowel movements, increased frequency and urgency, as well as nausea and stomach discomfort.

A Consumer Reports investigation also revealed that patients taking orlistat reported kidney, liver, and thyroid problems, as well as rectal bleeding. The publication stated the risks of orlistat outweighed the benefits, and that people should avoid the medication.


Along with prescription orlistat, a few new prescription diet pills have received FDA approval in recent years. Likewise, physicians may prescribe certain medications for weight loss as an "off-label" use of the drug.


Approved as an anti-seizure medication, topiramate is also known by the brand name Topamax. One of the primary side effects of use of the drug is weight loss, although it is an off-label use of the drug. Topamax is also prescribed to prevent migraine headaches.

While topiramate can generate weight loss, it has a number of serious dangers, as listed on the package insert.

  • Quitting the drug cold turkey can result in seizures, even when none were present before.
  • The British Journal of Ophthalmology reports topiramate may cause an emergent form of glaucoma called acute narrow angle glaucoma, which can lead to irreversible blindness.
  • Topamax may also cause osteoporosis and rickets.

The list of side effects for topiramate is extensive and includes:

  • Blurred vision
  • Difficulty breathing
  • Dizziness
  • Confusion
  • Exhaustion
  • Loss of appetite
  • Chest pain
  • Hair loss
  • Uncontrolled eye movements (nystagmus)
  • Speech and memory problems


Approved as a weight loss drug by the FDA in 2012 as a weight loss drug, Qsymia is a combination of topiramate and phentermine (the Phen half of Phen-Fen). Along with all of the dangers associated with topiramate, Qsymia also has side effects and dangers associated with phentermine, including:

  • Pulmonary hypertension
  • Heart valve problems
  • Nausea
  • Vomiting
  • Irritability
  • Headaches
  • Seizure
  • Vision problems


This new drug received FDA approval in 2012, but requires further FDA hearings for controlled substance scheduling before being available in the United States. Belviq alters brain chemistry, reducing appetite. According to the package insert, side effects may include:

  • Changes in mood or behavior including sadness and suicidal thoughts
  • Disassociation
  • Hallucinations
  • Extremely rigid muscles
  • Low blood sugar
  • Shortness of breath
  • Difficulty concentrating
  • Hypertension
  • Swelling of the extremities
  • Decreased white blood cell count
  • Anemia


A 1998 study showed the diabetes drug Metformin promoted weight loss in obese individuals with type 2 diabetes. Recent studies have confirmed these findings. American Family Physician also reports it can help weight loss in women with Polycystic Ovary Syndrome (PCOS). The package insert for Metformin lists a number of potential side effects and dangers, such as:

  • Lactic acidosis, which is a potentially fatal complication
  • Hypoglycemia
  • Hepatitis
  • Vitamin B12 malabsorption
  • Megaloblastic anemia

Seek Medical Supervision

It's never a good idea to self-prescribe any diet pill. Whether you take a weight loss supplement, an over-the-counter medication, or a prescription drug, it's important to weigh the benefits and risks before you begin taking diet pills. Your medical doctor or health care professional can help you determine whether the benefits outweigh the risks and monitor you for potential complications.

Along with working closely with your health care provider, educate yourself by reading the package insert and researching potential complications and side effects of the medication or supplement you choose. In this way, you can determine whether diet pills will enhance your weight loss program, or if it's just too risky.

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Dangers of Diet Pills