CLA Supplement
Benefits Vs. Side Effects

Tonalin CLA supplement (Conjugated Linoleic Acid) promises to promote weight loss by reducing body fat and increasing muscle mass - safely and without side effects.

According to Tonalin CLA, the leading manufacturer of CLA, this dietary supplement "changes body composition by reducing body fat and increasing or preserving lean muscle mass—giving you a leaner, healthier appearance".

They explain how this can be achieved:

Derived from natural safflower oil, CLA inhibits lipoprotein lipase, an enzyme that breaks down fat from our diets.

Once the fat is broken down, it is stored in the body. By suppressing this enzyme, CLA helps reduce the amount of fat that is broken down and, therefore, the amount of fat that is deposited and stored.

Combined with a balanced diet and exercise, CLA can help you lose body fat, and keep it off. You may drop a clothes size or two without yo-yoing between weight loss and gain.

It sounds promising - or does it?

What's CLA?

CLA is a short form for Conjugated Linoleic Acid. It is a form of essential fatty acid (EFA).

Now you are going to ask: What's an essential fatty acid?

They are fatty acids that cannot be manufactured internally within your body, and so must be consumed from your diet. There are two types of EFA: omega-3 and omega-6.

The health benefits of omega-3 fatty acids are wide-ranging and well-established in the scientific community. It has been shown to protect against heart and stroke diseases, reduce high blood pressure and relieve joint problems.

On the other hand, CLA is a family of at least 13 isomers of omega-6 fatty acids. It is found in small quantities in meat and dairy products.

Kangaroo may contain the highest concentration of CLA. Other foods rich in CLA are mutton and beef (especially those fed grass rather than grains) and eggs.

Now, here is a dilemma: if you are on a restricted diet, you probably are trying to cut back on meats and dairy products. It wouldn't make sense to increase you meat intake. This is when a CLA supplement may come in handy. In particular, it has been found to promote weight loss in 4 different ways.

How Does It Work?

According to Tonalin, the CLA supplement has undergone more than 600 studies in the past 25 years. The scientific studies have discovered 4 ways it may fight obesity:

  • Reduce fat storage after eating

  • Increase fat burning or metabolism

  • Increase the speed fat is broken down in fat cells

  • Reduce the number of fat cells in our bodies

Reduce Body Fat

According to Wikipedia, studies of CLA supplement in human diets show that it "tends to reduce body fat, particularly abdominal fat, improves serum lipid profiles, and decreases whole-body glucose uptake".

A 2001 study conducted by Parexel of Norway verified this claim.

20 people participated in the 12-week study. They have normal body weight and did physical exercise in a gym for 90 minutes 3 times weekly. They consumed either placebo or a CLA supplement (0.6 grams) three times daily as two capsules.

This is what the scientists found:

Body fat, measured using near infrared light, was significantly reduced in the CLA group during the study, but not in the placebo group. No effects on body weight were observed.

Tolerability was good and similar in the two groups. Thus CLA reduces body fat but not body weight in healthy exercising humans of normal body weight.

Another 2001 study conducted by the Scandinavian Clinical Research AS in Norway reached a similar conclusion. This study monitored 47 obese individuals for 12 weeks. The scientists concluded:

In conclusion, we want to emphasize that the beneficial effects of CLA with regard to [body fat mass] and [lean body mass] are promising.

The number of subjects in this study was relatively small and may thus be a limiting factor in reaching general conclusions. However, at present, a dose of 3.4 g CLA/day for 12 weeks seems to be sufficient to reduce BFM significantly in overweight and obese humans.

A conclusion regarding the optimal dose of CLA and duration of treatment cannot be made on the basis of these limited data, but the current data provide a solid platform for future studies.

Contradicting Results

A 2007 literature review conducted by the Hospital Universitario de La Princesa highlighted a concern shared by scientists regarding the CLA supplement - human studies have been inconsistent.

According to the researchers, CLA has many isomers of linoleic acid, of which the trans-10 and cis-12 isomers have significant weight loss effects in animal studies.

However, commercial CLA supplement contains trans-10, cis-12 and cis-9, trans-11 CLA isomers in diverse proportions. They concluded below:

Nevertheless, despite numerous studies on CLA effects on body composition for nearly a decade, the mechanisms by which CLA isomers elicit their effects remain largely unknown.

Experiments in humans have not been able to show a significant effect on body weight, body composition or weight regain related to either of the CLA isomers.

In fact, some studies suggest a tendency towards a decrease in body fat mass and an increase in body lean mass, while some others raise concern about the possibility of deleterious effects of trans-10,cis-12 CLA on lipid profile, glucose metabolism and insulin sensitivity.

What could be the explanation of these inconsistent results?

Is Dosage the Answer?

A 2007 study conducted by the University of Wisconsin School of Medicine and Public Health investigated possible reasons for inconsistent results observed in humans.

The scientists included 18 studies in their analysis. They investigated the effects of different CLA isomers on weight loss, and found no evidence that one isomer is better than the others.

They investigated the optimum duration of using a CLA supplement and found that the greatest effects were observed in the first 6 months. No benefits were observed after 2 years.

Finally the scientists concluded the following:

Given at a dose of 3.2 grams/day, CLA produces a modest loss in body fat in humans.

Any Side Effects?

There are few known side effects associated with a CLA supplement. Wikipedia summarizes quite nicely below:

There are concerns that the use of CLA by overweight people may tend to cause or to aggravate insulin resistance, which may increase their risk of developing diabetes. However, the evidence is controversial, and some studies showed no changes in insulin sensitivity.

In one study CLA produced a 32% increase in biliary cholesterol concentration which increases the chance of gallstone formation.


For anyone wanting to lose weight naturally, my first recommendation is green tea, and specifically a cup of high quality loose green tea.

However, green tea contains caffeine, so it may not be suitable for some people with medical conditions. Decaffeinated green tea may sound like an attractive option, but it is usually highly processed and low quality.

A CLA supplement offers many advantages. It has credible scientific studies as a fat burner. It has few side effects, and has undergone many scientific trials. And finally, being an omega-6 fatty acid, it is not a stimulant, i.e. it won't increase your metabolism.

Now, it is advisable to consult your medical adviser before using a CLA supplement.

A 2008 study published by the Covilha University Hospital in Portugal revealed the first case report of a woman suffering liver damage from consuming a CLA supplement.

Here is an abstract of the case report:

A 46-year-old female patient was referred to our department with presenting symptoms of asthenia, jaundice, and pruritus. There was no medical history or clinical evidence of viral hepatitis, autoimmune hepatitis, hemochromatosis, or Wilson's disease.

The patient revealed that 14 days prior to admission she had begun self-medicating with conjugated linoleic acid (CLA) to reduce body fat, leading to the suspicion of CLA hepatotoxicity, which was subsequently confirmed by a liver biopsy.

After the patient ceased to ingest CLA, liver enzymes levels normalized. To the best of our knowledge, this is the first report of hepatotoxicity due to CLA ingestion.

It is not clear what caused the liver damage and it the patient had overdosed, as this has previously been unheard of for CLA.

If you are getting a CLA supplement, you may want seek professional help before proceeding. Also, always get a Tonalin CLA, as this is the brand that has been tested in scientific studies.

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Thom E, Wadstein J, Gudmundsen O (2001). Conjugated linoleic acid reduces body fat in healthy exercising humans. J Int Med Res. 2001 Sep-Oct;29(5):392-6.

Henrietta Blankson, Jacob A. Stakkestad, Hans Fagertun, Erling Thom, Jan Wadstein and Ola Gudmundsen (2000). Conjugated Linoleic Acid Reduces Body Fat Mass in Overweight and Obese Humans. Journal of Nutrition. 2000;130:2943-2948.

Whigham LD, Watras AC, Schoeller DA (2007). Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans. Am J Clin Nutr. 2007 May;85(5):1203-11.

Ramos R, Mascarenhas J, Duarte P, Vicente C, Casteleiro C (2008). Conjugated Linoleic Acid-Induced Toxic Hepatitis: First Case Report. Dig Dis Sci. 2008 Aug 23.

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