Conjugated linoleic acid (CLA) is an omega-6 polyunsaturated essential fatty acid (EFA) which is formed from linoleic acid in bacterium via a specific isomerase (a type of enzyme).

This EFA is a mixture of positional and geometric isomers of linoleic acid. It is naturally occurring in meat and dairy products. In addition to reducing fat in the body, CLA has also been studied for its anticarcinogenic (anti-cancer) properties. Right now, CLA is of very high interest to scientists and nutritionists.

CLA has been quickly growing in popularity in the fitness world. Since its popularity is still relatively new, many people still have never heard of CLA. It is sold at almost all nutrition stores, and it is highly advertised on the Internet. Many competitive weightlifters and fitness performers have started taking this product and speak positively of its effects.

CLA usually comes in 1000 milligram softgels, and is supposed to be taken with meals three to five times daily. I have taken CLA many times before, and currently, in preparation for bodybuilding. The effects were definitely felt even though I had to take it for about thirty to forty-five days until I actually started seeing a change.

The Study

I found an experiment in a scientific journal at UGA that examined the effects of CLA on individuals. The experiment is titled, "Conjugated Linoleic Acid Reduces Body Fat Mass in Overweight and Obese Humans."1 Six years ago, the prevalence of obesity in the United States was about 70 million individuals.

In addition, the government spent an unbelievable 117 billion dollars trying to control this situation! I think that with these figures, and the studies conducted concerning CLA, it would definitely be worth trying out.

In this experiment, CLA was evaluated on its effects on lipolysis in adipose cells (the breakdown of fat in fat cells to free fatty acids), increased fatty acid oxidation from stored fat in both adipocytes (fat cells) and skeletal muscle. Many other experiments have shown beneficial for the subjects tested.

However, the subjects in previous tests were rats, chicks, mice, and pigs. The hope was that the results from these experiments would be indicative of the effects of CLA on humans.

In the experiments run on the listed animals, it had been found that lipase (enzymes that break down fat) activity increases in adipocytes and fatty acid oxidation increased due to increased carnitine palmitoyltransferase (just a long name for an enzyme involved in fat metabolism) activity in adipocytes and skeletal muscle.

The Subjects

The subjects in this experiment were 20 men and 40 women, at least 18 years old, with a body mass index (BMI) range of 25.1 kg/m2 to 34.9 kg /m2. This BMI range encompasses both the overweight and the obese. The proposed outcome of the experiment is that benefits from increasing CLA intake in overweight and obese individuals with regards to body fat mass, lean boy mass, overall weight reductions, and blood lipids will be achieved.

The study design was a single-center, randomized, double-blind, placebo-controlled study with five parallel groups (statistical jargon, basically, this was a good set-up for an experiment). The placebo (fake pill) was 9 grams of olive oil per day in place of CLA. The amounts of CLA used were 1.7, 3.4, 5.1, and 6.8 grams of CLA per day.

Subjects took three doses total per day at breakfast, lunch, dinner for a time span of 12 weeks. Since the design was double-blind, the distributor of the capsules and the subjects were unaware of who was getting what. Each subject received 4 capsules per dosage.

Each capsule was either olive oil (the placebo) or CLA. The placebo group always received 4 capsules of olive oil, while the group with the highest CLA intake always received 4 capsules of CLA. All CLA capsules were 1000mg with 75% pure CLA.

The subjects of the experiment made a total of three clinical visits within the 12 week period. In the clinic, the subjects were evaluated on body fat mass, lean body mass, body weight, blood pressure, and heart rate.

Also, subjects were additionally tested on factors such as physical performance in order to determine any variables that would throw off the results of the effects of CLA, such as performing exercise. Also, blood samples were taken and evaluated on the basis of safety to make sure the subjects' health was not in jeopardy.

Questionnaires were distributed at week 0 and week 12 to the subjects. The matters addressed involved perceived noticeable changes in quality of life such as differences in vitality, overall work capacity, sleep, appetite, mood, and leisure activity. The information given by the subjects was recorded and used for statistical analysis.

The Results

At the end of the experiment, among the characteristics of the subjects that did not change were height, weight, and BMI. 47 subjects actually completed the study from an initial 60 individuals. Fortunately, the percentages of individuals that remained in each group was still relatively consistent ranging from 82%-88%.

There was a significant difference in body fat mass in the groups taking 1.7 grams, 3.4 grams, and 6.8 grams as a whole, and significant differences within the 3.4 grams and 6.8 grams groups. There was no significant difference among groups in regards to lean body mass, but the 6.8 gram group increased in lean body mass significantly.

As a whole, the 6.8 gram group also increased physical activity, while the 5.1 gram group decreased physical activity. In this situation, increased physical activity could have increased the effects of taking CLA for the 6.8 gram group.

With regards to the blood samples drawn, there were no clinically important changes in blood content. Regarding the questionnaire, only the CLA groups reported an increase in the quality of life after 12 weeks.

Unfortunately, 13 individuals dropped out of the experiment. Overall, the experiment showed that with increased CLA consumption, one who is obese or overweight can increase lean body mass slightly, decrease body fat mass significantly, improve muscle strength, and slightly decrease low-density lipoprotein levels in the blood (which is good as far as future health goes).

However, all CLA groups showed a decrease in high-density lipoprotein levels at the end of 12 weeks. This is a slight draw back in evaluating the positive effects of CLA.

I think that this experiment produced some definite benefits for those who are overweight and obese and take CLA regularly. I also think that this experiment will lead to further experimentation on CLA consumption. This experiment suggests that there may be a synergistic effect of increasing physical activity and taking CLA with regards to overall body composition.

I know, the technical terms can kind of make you bogged down, but here's the bottom line: Your body can use free fatty acids as a fuel source from the breakdown of fat cells due to actions caused by CLA. As a result, if you have more free fatty acids in your blood while you are exercising, you will be able to burn more fat while exercising.

However, if you have all of those free fatty acids in your blood and you don't exercise, you will not burn fat at a high rate. This is actually a modified report that I wrote for a nutrition class that I was taking this past semester. My professor thought it was very interesting, so I figured that it was worth sharing to those who are trying to slim up before summer.

  1. Blankson, H., Fagertun, H., Gudmundsen, O., Stakkestad, J.A., Thom, & E., Wadstein, J., Conjugated Linoleic Acid Reduces Body Fat Mass in Overweight and Obese HumansJ. Nutr., 130: 2943-2948, 2000.

About the Author

David Knowles

David Knowles

I began lifting when I was very young, around eight years old. My dad had always been a big guy, so I started going to the gym with him to watch him workout.

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