OTC slimming pills - pros and cons

Confused about the plethora of over-the-counter slimming pills, drops and shakes? DietDoc has compiled a list of the most common ingredients, the potential risks and the results you can expect.

2011 is only 3 weeks old and readers are already asking me what I think of different over-the-counter (OTC) slimming pills, drops and shakes. To clarify matters, I have made a summary of the effects the various herbs and other compounds that are commonly used in OTC. Not only the potential side-effects, but also an assessment of the success or lack of success one can expect from such products, have been listed. I hope this will help slimmers to make informed choices when they consider using OTC slimming pills.

Typical OTC slimming pill ingredients

Slimming is a mega-billion rand industry throughout the world and South Africa is no exception. The use of OTC slimming products in the USA is estimated to exceed $13 billion, while sales of weight loss supplements in Western Europe exceed $1.4 billion (ScienceDaily, 2010).

Newspapers, magazines, TV, radio, billboards, supermarkets, chemist and health shops advertise products which promise painless, effortless and safe weight loss. A random survey conducted by DietDoc in two major pharmacies of some of the most popular OTC slimming products sold in South Africa, showed that most of these diet pills typically contain the following ingredients in varying concentrations and combinations:

  • Acetic acid - Apple cider vinegar
  • Amino acids - BCAA (branched-chain amino acids), L-glutamine, L-glycine, Taurine, L-tyrosine, DL- phenylalanine
  • Caffeine or guarana
  • L-carnitine
  • Conjugated linoleic acid (CLA)
  • Creatine
  • Epinephrine in various forms (pharmacological and herbal products)
  • Fibre - guar gum, pectin, psyllium, methylcellulose, bran
  • Herbal extracts - Guarana, Cayenne, Dandelion root, Ginseng, Uva ursi, Bitter Orange Extract or Citrus Aurantium, Ginger root, White Willow bark
  • Hydroxycitrine or -citrate (HCA) or Garcinia cambogia
  • Kelp and seaweed extracts
  • Phenolphthalein
  • Pyruvate
  • Trace elements - Chromium, Boron, Selenium
  • Vitamins in high doses

To illustrate the potential risks associated with the use of OTC slimming products, the composition of a leading herbal slimming pill that recently made headline news in South Africa, together with the potential side-effects of such ingredients as identified in the medical literature, are listed in the following table.

Table:             Common ingredients, effects and side-effects in a popular South African OTC slimming pills



Side-effects/Cautions  (Mahan & Escott-Stump ,2007;Martindale, 2009; MIMS 2006/7)

Bitter Orange Extract (Citrus Aurantium, Bigarade Orange or Neroli) contains Synephrine

  • Suppresses appetite
  • Increases energy
  • Lifts the mood


  • Nausea, vomiting, dry mouth, thirst, problems with urination, hypertension, rapid, irregular heartbeat, cardiac arrhythmias, angina pain, palpitations, heart arrest, fear, anxiety, restlessness, insomnia, dizziness, faintness, flushing, tremor, muscle weakness, headache, irritability, psychotic states, altered metabolism
  • Contraindications:Should not be used in pregnancy, breast-feeding, hypertension, hyperthyroidism, diabetes, closed-angle glaucoma, heart disease, prostate enlargement, children and teenagers
  • Special warning:Can become addictive. Can be abused. Effect wears off over time, requiring larger doses

Cassia seed & Aloe vera

  • Laxatives


  • If taken in excess, may cause diarrhoea, upset fluid & electrolyte balances, disrupt normal peristalsis & prevent absorption of vital nutrients leading to nutrient deficiencies

Alisma orientalis

  • Diuretic
  • If taken in excess, may cause dehydration & upset fluid & electrolyte balance (loss of potassium & sodium)
  • Users of this slimming pill are instructed to drink large volumes of water, which may be related to the presence of a diuretic in the formulation
  • Excess water intake can be fatal as demonstrated during Comrades’ Marathons, where athletes have died as a result of drinking too much water and reducing potassium and sodium to dangerously low levels


(Biological compound, produced in the human body, found in protein foods)


  • Transports long-chain fatty acids into mitochondria to serve as fuel during exercise
  • Improves cardiovascular function and muscle strength
  • Decreases fatigue
  • May decrease body fat if combined with a strenuous exercise programme
  • No evidence that it removes fat from fat depots
  • No evidence that L-carnitine deficiency is common
  • Suppresses thyroid function & should not be used by patients with hypothyroidism (Benvenga,2005)

Lotus or Water Lily


  • Aphrodisiac
  • Sedative
  • May be added to make users ‘feel euphoric’
  • Dried flowers of certain species of Nymphaea & Nelumbo are sometimes smoked, made into a tea, or macerated in alcohol for a mild sedative effect

Evening Primrose Oil

  • Omega-6 FA
  • Probably harmless

Dietary fibre

  • Mild laxative
  • Bulking agent
  • May cause abdominal distension


  • Sweetening agent
  • May improve taste of product

Lack of efficacy

Papers presented at the recent XI Congress on Obesity (Stockholm, 2010) by Dr Thomas Ellrott (Göttingen Medical School, Germany) and Dr Igho Onakpoya (Universities of Exeter & Plymouth, UK), found that the following OTC slimming pill ingredients had no effect on weight loss when compared to placebo (ScienceDaily, 2010):

  • L-carnitine
  • Polyglucosamine
  • Cabbage powder
  • Guarana
  • Bean or Konjac extract
  • Fibre
  • Sodium alginate
  • Selected plant extracts
  • Chromium picolinate
  • Ephedra
  • Bitter orange
  • CLA
  • Guar gum
  • Glucomannan
  • Chitosan
  • Green tea


  • Because of the Obesity Epidemic, the SA public will do anything to lose weight and expose themselves to the dangers of fad slimming diets and OTC slimming pills
  • There are no checks and balances in place to stop the spread of inaccurate dietary information and the proliferation of fad diets and potentially dangerous slimming products

It should be evident from the information listed above, that the majority of these OTC slimming products are potentially dangerous and often don’t produce any weight loss. I would urge readers to rather spend their money on consulting a registered dietician or joining a gym or Walk for Life so that they can lose weight safely.

 - (Dr IV van Heerden, DietDoc, January 2011)


(ScienceDaily (2010). No evidence that popular slimming supplements facilitate weight loss, new research finds. (www.sciencedaily.com/releases/2010/07/100712103445.htm); Mahan LK, Escott-Stump S (2007). Krause’s Food, Nutrition & Diet Therapy. 12thEdition. WB Saunders Co, Philadelphia; Martindale. The Extra Pharmacopoeia.(2009). 36thEdition. Pharmaceutical Press, London; MIMS (2006/7). Complementary Desk Reference, Vol 2. MIMS (a division of Johncom Media Investments). Johannesburg; Benvenga S, 2005. Effects of L-carnitine on thyroid hormone metabolism and on physical exercise tolerance. Horm Metab Res, 37(9):566-71.)

Any questions? Ask DietDoc

Read more:

Slimming herbs dissected
OTC diet pill as effective as placebo
Carbs: Public Enemy No 1?

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