Weight Loss Supplements, Diet Pills, Fat Burners and Skinny Pills

Weight loss pills, diet pills, and weight loss supplements.
Prescription Diet pills can assist in losing weight, but are they worth the possible severe side effects?

Weight Loss Pills, Skinny Pills, and Diet Pills – What Are They?

Weight loss pills, also known as diet pills and skinny pills, are any sort of pills intended to help the user lose weight. Weight loss pills are available by prescription, and they can also commonly be found over the counter as non-prescription drugs and dietary supplements.

Most are primarily made from natural ingredients (i.e. herbal extracts), though some over the counter diet pills are based on pharmaceutical compounds (i.e. orlistat/Alli, a type of over the counter weight loss pill). Many fat loss pills are intended to be used in conjunction with a modified diet and exercise.

A skinny pill usually delivers its results by increasing feelings of fullness or increasing metabolism to burn fat:

  • Appetite suppressants are taken to reduce feelings of hunger and make the user feel full. This helps to reduce overall calorie intake, thus promoting weight loss.1
  • Fat burners are a broader type of weight loss supplement that are usually used to burn calories. Many fat burning pills work by increasing metabolism of fats and carbohydrates, but some derive their effects by lowering fat absorption from dietary sources.2
  • Meal replacers work similarly to appetite suppressants – both are supposed to reduce overall calorie consumption and suppress appetite. Unlike appetite suppressants, meal replacers are intended to be taken in place of a meal such as breakfast or dinner.

Common Weight Loss Pill Ingredients

  • Caffeine
  • Capsaicin (cayenne pepper/chili pepper)
  • Carnitine
  • Chromium
  • Conjugated linoleic acid (CLA)
  • Forskolin
  • Garcinia cambogia
  • Ginseng
  • Green coffee extract
  • Green tea extract
  • Guar gum
  • Hoodia gordonii
  • Raspberry ketone
  • White kidney bean

Weight Loss and Diet Pill Controversy

Some weight loss pills have generated much controversy in recent years, due to fraudulent marketing claims and serious adverse health effects. In some countries, dietary supplements do not have to be licensed and approved by government agencies before being sold. It is important to note that US FDA approved weight loss supplements do not exist, because the FDA does not review dietary supplements before they are put on the market.

“Under the Federal Food, Drug and Cosmetics Act (as amended by the Dietary Supplement Health and Education Act of 1994), dietary supplement firms do not need FDA approval prior to marketing their products. It is the company’s responsibility to make sure its products are safe and that any claims made about such products are true”, says the FDA.3 However, in cases where supplements are found to cause serious negative health effects, the FDA will often seize and ban the sale of supplements containing the ingredient found to be responsible. The FDA may also issue a public warning advising consumers not to buy a certain product if the product is found to contain unlisted ingredients.

Weight Loss Pills survey results
A US survey showed that there are widespread misconceptions about the safety of dietary supplements. The three true/false questions shown in the above table are all false, but the survey showed that most people believed the statements were true (represented by the percentages shown in the columns on the right.5)

Research has shown that attempts to mislead consumers about safety information by weight loss supplement companies are not uncommon. A 2008 survey showed that many US consumers hold misconceptions about the safety of fat loss supplements, with many respondents believing that dietary supplements are FDA-tested.4, 5 The survey suggests that increased consumer knowledge could help protect consumers from choosing unsafe products.5 Thus, if you’re looking for safe diet pills or safe weight loss supplements, it is important to research any product before buying; read up on the company, search for reviews, and look at the listed ingredients. Be wary of any product that does not appear to have any user reviews.

Natural Weight Loss Supplements

Natural weight loss supplements are products primarily made from ingredients that occur in nature, rather than synthetic compounds created in a lab. They also tend to be sold over the counter, instead of requiring a prescription. Since weight loss drugs often come with a number of intense side effects, natural weight loss pills can be a safer alternative, with less risk of experiencing serious side effects or health issues.6 These supplements contain ingredients known to be natural fat burners and natural appetite suppressants, such as green tea and chili pepper extracts.7

Natural Weight Loss Supplement Efficacy

There are numerous natural ingredients that have been claimed to help reduce weight. Many of these ingredients have been shown to have multiple beneficial effects on weight loss. Some ingredients have multiple high-quality clinical trials to support their effectiveness; for example, capsaicin has been shown to increase fat metabolism and reduce appetite.8 Thus, an effective natural weight loss supplement can be a useful dietary addition for those looking to lose weight.

However, for some of these ingredients, there is not enough scientific evidence to support their effectiveness. Some natural ingredients have not been thoroughly studied in relation to weight loss, so no conclusions can be made about these compounds.9 For example, raspberry ketone, a compound that gives scent to raspberries, has not been proven to have any effects on weight in studies involving humans; raspberry ketone has only been shown to affect weight in animal trials.9 Even though natural ingredients can support weight loss, not all have been proven effective – researching ingredients before buying can help you avoid ineffective products.

Natural Weight Loss Supplement Side Effects & Risks

Many natural ingredients used in diet supplements have only been associated with mild side effects when consumed in moderate amounts.10 However, there is a lack of data for many natural ingredients, especially when taken in high doses or when taken for an extended period of time. Additionally, though some countries review supplements for safety, not all countries test and approve dietary supplements before allowing them to go to market.

In the US, natural fat burning supplements, appetite suppressants, and other weight loss supplements are regulated as dietary supplements, meaning that the FDA does not test and approve such supplements for safety.3

However, in Canada, Health Canada regulates dietary supplements for safety, and products must be licensed before being sold on the market. Products that have been reviewed by Health Canada are marked with a Natural Product Number (NPN) or a Homeopathic Medicine Number (DIN-HM) on the label.11

Prescription Diet Pills

Prescription weight loss pills are a type of medication prescribed to help the patient lose weight, in cases where the patient’s weight has severe effects on health – for example, when weight increases the chance of developing health conditions such as cardiovascular disease and type 2 diabetes. Weight loss medications are usually intended to be prescribed when the patient has a body mass index (BMI) greater than 30, and the patient has been unsuccessful at losing weight through exercise and dietary modifications.12 Anyone with a BMI under 25 should not use prescription pills to lose weight.

Prescription fat burner pills and prescription appetite suppressants are intended to be used alongside a modified diet and exercise program. Most evidence shows that weight loss drugs only have a moderate effect on weight loss, while having moderate to severe side effects.12 Consequently, taking prescription pills to lose weight is not a recommended method of weight loss for most people.

Prescription diet pills effectiveness
Pharmaceutical weight loss drugs only have a moderate effect on weight, but can have severe side effects.13

Prescription Diet Pill Side Effects & Risks

Weight loss medication drugs have many side effects well-documented in scientific literature. For example, orlistat, which is available by prescription and over the counter in the US, works to reduce weight by blocking fat absorption. Fat is then excreted rather than absorbed, but this mechanism causes very uncomfortable side effects such as flatulence, loss of control of bowel movements, diarrhea, oily spotting, and bloating.13 Orlistat is the only weight loss medication that has been shown to be safe for long-term use, though there have been reports of liver injury associated with orlistat.14 It is approved for over the counter sale in some countries, including the US.

In addition to side effects, multiple prescription weight loss medications have been associated with serious health conditions. Sibutramine, which was withdrawn from the US and Canada in 2010, was associated with heart attacks and strokes.15 Rimonabant, an appetite suppressant shown to reduce weight, caused serious mental health issues such as depression, anxiety, and suicidal tendencies. Its approval has been suspended in Europe, and it was never approved in the US.16 Fen-phen, another drug, was taken off the market after it was found to cause heart valve problems, valvular disease, and even death in some cases; these health problems resulted in millions of dollars of lawsuits.17 

Note: Supplement Analyst does not review any prescription drugs, medications, or other controlled substances.

Weight Loss Pills for Women

Thinking of buying a weight loss supplement? Click here for the latest buying guide.

Generally, women have a higher body fat percentage than men. The mechanisms behind this action are not fully clear, but women tend to gain body fat more easily than men, and more of this fat is stored around the hips and buttocks.18 Thus, women have a harder time losing body fat, and often have a harder time losing fat stored around the hips.18 Women are more likely to go through drastic weight changes where their nutritional needs vary greatly throughout their lifetime – for example, during pregnancy.

As a result, there are many weight loss supplements for women that are intended to address women’s unique needs when losing weight. Specifically-formulated diet pills for women as well as fat burners for women can help women maintain a healthy weight. Some are intended for certain periods during a woman’s life; for example, weight loss supplements intended to help lose weight after pregnancy, and supplements aimed at menopausal women.

These weight loss supplements can be a more effective choice for women than generalized weight loss products, and these products are usually better at supporting women’s health.

Weight Loss Pills for Men

Thinking of buying a weight loss supplement? Click here for the latest buying guide.

Men’s body composition differs from women’s as they tend to have more muscle mass and a lower body fat percentage.18 Men also tend to store fat in different places – men store more fat around the abdomen (the so-called beer belly).

Men’s body composition is largely due to testosterone, the male sex hormone that is responsible for many of the differences between men and women. Men tend to have a higher muscle mass when they have high testosterone levels. Since testosterone levels drop over time, men tend to gain more weight as they get older, unlike women, whose weight often fluctuates over time.

As a result, there are many weight loss supplements for men that are used to help men reach specific goals, and focus on men’s health needs. Some diet pills for men are aimed at helping men change their body composition by reducing body fat and building muscle mass. These supplements are usually intended to be used in conjunction with an exercise and diet plan to build muscle and lose fat mass. Some weight loss pills for men are intended for older men, who have lower testosterone levels and tend to gain fat more quickly as a result.

Men’s weight loss supplements are better at addressing men’s specific health needs than general weight loss supplements, so a diet pill intended for men may be more effective at helping men lose weight than a general supplement.

GNC Weight Loss – and Other Retailers

Supplements for weight loss can be purchased at pharmacies, drugs stores, online, or your local sports nutrition store like GNC.

Weight Loss Reviews

Click here for the most comprehensive weight loss supplement reviews.


  1. Wilbert, B., Mohundro, B. L., Shaw, V., & Andres, A. (2011). Appetite suppressants as adjuncts for weight loss. American Family Physician, 83 (7), 1.
  2. Jeukendrup, A. E.,Randell, R (2011). Fat burners: nutrition supplements that increase fat metabolism. Obesity Reviews, 12 (10): 841-51.
  3. S. Food and Drug Administration (2015, Jan. 5). Beware of Products Promising Miracle Weight Loss. Retrieved 4 August 2016.
  4. Nazeri, A., Massumi, A., Wilson, et al (2009). Arrhythmogenicity of weight-loss supplements marketed on the internet.Heart Rhythm, 6 (5), 658-662.
  5. Pillitteri, J., Shiffman, S., Rohay, J., Harkins, A., Burton, S., & Wadden, T. (2008). Use of dietary supplements for weight loss in the united states: Results of a national survey.Obesity, 16 (4), 790-796.
  6. Brudnak, M. A. (2002). Weight-loss drugs and supplements: Are there safer alternatives?Medical Hypotheses, 58 (1), 28-33.
  7. Poddar, K., Kolge, S., Bezman, L., Mullin, G. E., & Cheskin, L. J. (2011). Nutraceutical supplements for weight loss: A systematic review.Nutrition in Clinical Practice, 26 (5), 539-552.
  8. Mullin, G. E. (2014). Supplements for weight loss: Hype or help for obesity?Nutrition in Clinical Practice, 29 (6), 842-843.
  9. Ríos-Hoyo, A. & Gutiérrez-Salmeán, G. (2016). New Dietary Supplements for Obesity: What We Currently Know. Current Obesity Reports, 5 (2), 262-270.
  10. Mullin, G. E. (2015). Supplements for weight loss: Hype or help for obesity? part III.Nutrition in Clinical Practice, 30 (3), 446-449.
  11. Natural and Non-prescription Health Products Directorate. Questions from Consumers – Regulation of Natural Health Products. Health Canada. Retrieved 10 August 2016.
  12. Snow, V., Barry, P., Fitterman, N., Qaseem, A., Weiss, K. (2005). Pharmacologic and surgical management of obesity in primary care: a clinical practice guideline from the American College of Physicians. Annals of Internal Medicine, 142 (7), 525–31.
  13. Kang, J. G., & Park, C. (2012). Anti-obesity drugs: A review about their effects and safety.Diabetes & Metabolism Journal, 36 (1), 13-25.
  14. S. Food and Drug Administration (2010, May 26). Questions and Answers: Orlistat and Severe Liver Injury. Retrieved 5 August 2016.
  15. James, P. T, Caterson, I. D., Coutinho W., et al (2010). Effect of sibutramine on cardiovascular outcomes in overweight and obese subjects. New England Journal of Medicine, 363: 905-917.
  16. Derosa, G., & Maffioli, P. (2012). Anti-obesity drugs: A review about their effects and their safety.Expert Opinion on Drug Safety, 11 (3), 459-471.
  17. S. Food and Drugs Administration (1997, Sept. 15). FDA Announces Withdrawal Fenfluramine and Dexfenfluramine (Fen-Phen). Retrieved 5 August 2016.
  18. Blaak, E. (2001). Gender differences in fat metabolism. Current Opinion in Clinical Nutrition and Metabolic Care, 4 (6), 499-502.