Are Weight-Loss Drugs/Pills Safe? How Do Weight Loss Pills Work?

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Are Weight-Loss Drugs/Pills Safe? How Do Weight Loss Pills Work?

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“There’s an incredibly strong societal pressure to lose weight and a desire to do it quickly. This pressure can lead people to consider shortcuts, like weight loss pills.” Explains Dr. Yoni Freedhoff who is a family medicine professor at the University of Ottawa. 

In the age of Instagram-perfect bodies and quick fixes, we wonder: Are weight loss pills truly a safe solution to shed those extra pounds? The booming popularity of these magic pills for weight loss is undeniable.

“Obesity and overweight are real, complex, and far-reaching public health issues,” says Dr. Caroline Apovian, a renowned expert in obesity management. “Yet, the lure of a quick-fix pill can sometimes overpower the well-established fact that sustainable weight management takes time and effort.”

Are Weight Loss Pills Safe?

As per the U.S. Food and Drug Administration (FDA), the safety and efficacy of these products can be questionable. In recent years, several weight loss supplements have been linked to serious health problems, including liver damage, kidney issues, and heart problems (1).

Dr. Pieter Cohen, an Associate Professor of Medicine at Harvard Medical School, has extensively studied dietary supplements. He asserts that many weight loss pills contain pharmaceutical drugs, heavy metals, and other substances that aren’t listed on the label. They are promoted as natural and safe. Dr. Cohen’s studies have suggested that reality is further from the truth (2). 

Furthermore, the FDA notes that a significant proportion of weight loss supplements are tainted with prescription drug ingredients or other substances that aren’t listed on the label. This lack of transparency can lead to unexpected health risks, especially when these products interact with other medications or underlying health conditions (3).

On the other hand, prescription weight loss medications that have undergone rigorous clinical testing and are regulated by the FDA are generally considered safe for use under a healthcare provider’s supervision. However, even diet pills are not without side effects and should be used to treat overweight in conjunction with diet and exercise.

To answer the question, “Are weight loss pills safe?” Well, the safety of weight loss pills depends significantly on their composition, source, and the individual’s health status. It is always recommended to consult with a healthcare provider before starting any weight loss regimen, including supplements or over-the-counter weight loss pills.

Which Weight-Loss Drugs Are Approved by FDA

The FDA has greenlighted several prescription drugs for weight management to help you lose weight, including Orlistat for long-term use. However, Setmelanotide (IMCIVREE) is reserved for those with specific genetic disorders confirmed via testing. These FDA-approved prescription medications to treat overweight can be continued provided they’re beneficial and don’t cause severe side effects.

Conversely, certain appetite-suppressing weight loss drugs are approved by the FDA for short-term use, usually up to 12 weeks. Despite being sometimes prescribed longer, their long-term safety and effectiveness remain under-researched. It’s important to note that these weight management medications should be avoided during pregnancy or if planning to conceive, to prevent potential fetal harm.

Here is a list of some of the known weight loss drugs and their effects. 

Weight Management DrugsPrescribed ForFunctionalityCommon Side EffectsCautions
Orlistat (Xenical, Alli)Adults and children 12 and olderReduces fat absorption in the gutStomach discomfort, gas, oily stool leakage, diarrheaReports of severe liver injury, avoid with cyclosporine, daily multivitamin required
Phentermine-Topiramate (Qsymia)AdultsPhentermine curbs appetite and topiramate treats seizures/migrainesDry mouth, constipation, altered taste, dizziness, tingling extremities, insomniaAvoid with glaucoma or hyperthyroidism, risk of birth defects, not suitable during breastfeeding
Naltrexone-Bupropion (Contrave)AdultsNaltrexone treats substance dependence, and bupropion aids in depression and smoking cessationInsomnia, dry mouth, constipation, dizziness, diarrhea, nausea, vomiting, increased blood pressure and heart rate, possible liver damageAvoid with high blood pressure, seizures, history of eating disorders, opioid dependence, or bupropion use, which may induce suicidal thoughts
Liraglutide (Saxenda)Adults and children 12 and olderMirrors GLP-1 hormone to regulate appetiteNausea, diarrhea, constipation, abdominal pain, headache, increased heart rateRisk of pancreatitis found to cause rare thyroid tumors in animals
Semaglutide (Wegovy)AdultsMimics GLP-1 hormone to manage appetiteFatigue, headache, abdominal pain, constipation, vomiting, diarrhea, nauseaDo not use with other Semaglutide products, GLP-1 agonists, or other weight loss products, risk of pancreatitis, linked to rare thyroid tumors in animals
Setmelanotide (IMCIVREE)People aged 6 and older with specific genetic conditionsMay enhance feelings of fullness and boost resting metabolismNausea, injection site reaction, skin darkening, disturbance in sexual arousal, depressive and suicidal thoughtsRisks to low birthweight neonates and infants due to benzyl alcohol, genetic testing required for rare genetic diseases, not suitable during pregnancy or breastfeeding
Other Appetite Suppressants (Phentermine, Benzphetamine, Diethylpropion, Phendimetrazine)AdultsIncrease brain chemicals to suppress hungerDry mouth, constipation, insomnia, dizziness, restlessness, headache, elevated blood pressure, and heart rateAvoid with heart disease, high blood pressure, hyperthyroidism, or glaucoma, only drugs approved for short-term use (up to 12 weeks), inform health care provider about severe anxiety or mental health problems

Table – National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (4).

How Do Weight Loss Pills Work?

The way weight-loss pills function is typically categorized into appetite control, metabolic acceleration, fat burning, total body mass index (BMI), or a blend of these mechanisms.


Certain supplements, such as those containing phentermine, work by deceiving the brain into believing it’s satiated (5).

They impede the hunger messages that usually induce cravings by affecting the adrenal gland. This leads to a reduction in caloric intake, supporting weight loss endeavors.


B6 and B12 vitamins are often hailed for their role in weight loss. Vitamin B6 aids in transforming glycogen into glucose (6).

This enhances energy levels without the need for additional carbs. It may also deter fat accumulation. Vitamin B12, conversely, stimulates metabolism and energizes the body, fostering more significant weight loss and promoting digestive health.


Fat burners often contain caffeine which intends to augment metabolic rate (7).

According to Dr. Bhargava, they may cause palpitations, dry mouth, and fatigue. Dr. Manish Motwani emphasizes that they might assist in blocking fat and increasing metabolism but warns about potential hypertension risk. The consensus among experts seems to be a preference for natural weight loss methods over-reliance on fat burners.

Weight loss pills
Weight loss pills work by various mechanisms.


As a subset of weight loss pills, appetite suppressants aim to reduce caloric intake by curbing hunger or creating an early sense of fullness. While deemed useful for overweight individuals, Dr. Motwani points out that misuse could lead to adverse effects such as diarrhea, dizziness, nausea, and more.

Potential Side Effects of Taking Weight Loss Pills

The consequences of using supplements for weight loss are multifaceted. Proper medical guidance and a thorough understanding of both short-term and long-term effects are essential to minimize risks and ensure health and well-being.

Short-term Side Effects: What You Might Experience

Gastrointestinal Issues

Orlistat, an FDA-approved drug for weight loss, blocks fat absorption in the intestines, leading to gastrointestinal side effects like diarrhea, flatulence, and oily stools. These symptoms are particularly common during the initial phase of treatment and can be distressing for users (8).

Heart Palpitations

Ephedrine is a common component in weight loss supplements. It has been associated with heart palpitations and even severe cardiovascular events. This stimulant increases heart rate, possibly leading to serious cardiac issues in predisposed individuals (9).

Headaches and Dizziness

Appetite suppressants can cause headaches, insomnia, dry mouth, and dizziness as side effects. These are believed to be related to changes in blood pressure and brain neurotransmitter levels that the drugs induce to suppress appetite (10).

Mood Changes

As Dr. Sidney Wolfe notes the stimulant content in some weight loss pills can affect mental well-being, causing anxiety or mood swings. These symptoms can be distressing and may hinder a person’s daily activities.

Long-term Side Effects

Heart and Liver Damage

Long-term consumption of some weight loss supplements has been found to cause irreversible heart and liver damage. This is often due to unidentified or harmful substances within these supplements, leading to chronic health conditions.

Dependency and Addiction

Continued use of pills containing stimulants like ephedrine can lead to dependence or addiction, a severe mental health disorder requiring specialized treatment and care (11).

Increased Risk of Mental Health Disorders

A correlation between the extended use of weight loss pills and mental health disorders like depression and anxiety has been found. This link might be related to the physical and psychological stress imposed by constant weight management efforts (12).

Potential Increased Mortality

As per the studies, there’s evidence suggesting that the long-term consumption of weight loss supplements might even lead to increased mortality. This is a significant concern that underscores the need for rigorous regulation and transparent labeling (13).

Why Prefer Diet and Exercise Over Pills to Treat Overweight and Obesity

One of the most compelling reasons to favor a healthy diet and exercise over weight loss pills is the holistic health benefits they offer. Dr. Mark Hyman, a notable figure in the world of nutrition, firmly believes that the path to optimum health is through ” read food and physical activity,” a view that underscores the comprehensive benefits of a natural approach to weight management.

<<<<< Read how to use food to improve your weight loss efforts>>>>

Sustainability of Results

A weight loss journey rooted in diet modifications and regular exercise usually ensures sustainable results. As per research, achieving weight loss by naturally adapting to healthy lifestyle changes significantly reduces the likelihood of weight regain in the future (14). 

Absence of Pharmacological Side Effects

Weight loss pills often come with a slew of potential side effects, a concern that’s non-existent when you rely on diet and exercise. Dr. David Katz, a preventive medicine specialist, frequently emphasizes how the human anatomy and physiology are primed to respond positively to traditional weight regulation mechanisms—diet and exercise.

The Ripple Effect of Balanced Diet and Regular Exercise

Transitioning to a balanced diet and engaging in consistent physical activity have ripple effects that extend beyond mere weight loss:

  • Cardiovascular Health: Regular exercise and a heart-healthy diet can improve cardiovascular functions, reducing the risks of heart disease (15).
  • Mental Well-being: The research is very clear. Physical activity has been linked to improved mood and reduced symptoms of depression and anxiety (16). 
  • Enhanced Immunity: A nutritious diet boosts immune responses, preparing the body to better fight off diseases (17). 

Moreover, the cost implications of relying on diet and exercise are far more favorable. Weight loss pills can be a continuous expense, and their potential side effects might lead to additional medical costs.

In contrast, investing in a balanced diet, while occasionally pricier than processed foods, can be more economical when we factor in the potential savings from avoiding medical bills related to the side effects of weight loss pills.

When considering obesity and weight management, diet and exercise present a comprehensive, enduring, and risk-free approach, clearly outshining the temporary fixes offered by weight loss pills.

The Gist

The journey of understanding the intricacies of weight loss pills, from their modes of operation to their potential short-term and long-term side effects, sheds light on the complexities surrounding their use. With the comprehensive benefits and sustainable results of natural methods like diet and exercise, the choice becomes more apparent.

While weight loss pills might offer enticing promises of rapid results, their associated risks and the lack of sustainability make them a less favorable option for many. On the other hand, diet, and exercise, being rooted in time-tested principles, offer a holistic, sustainable, and risk-free approach to weight management.

In directly addressing the central question of the blog: “Are Weight Loss Pills Safe?” the answer is, it depends. While certain FDA-approved pills may be safe and effective for some individuals under medical guidance, they are not without risks. Additionally, when juxtaposed with the overarching benefits of diet and exercise, pills seem to be a less optimal choice for the broader population.

In conclusion, for those seeking a comprehensive, lasting, and health-conscious approach to total body weight management, prioritizing diet and exercise over pills seems to be a well-researched and safer recommendation.