Conjugated Linoleic Acid And Fat Loss: A Scientific Evaluation

Obesity is manifesting as a global epidemic. And losing weight is definitely not an easy task. So it is pretty common to look forward for some medication or supplement that could make weight loss a tad bit easier.

But from myriad of options available it is difficult to ascertain which one is actually effective. Today we are going to cover Conjugated Linoleic Acid, a weight loss supplement that you must have already heard of.

What is Conjugated linoleic acid?

Linoleic acid is an omega-6 fatty acid found mainly in vegetable oils. Conjugated linoleic acid is an altered form of linoleic acid. It is a poly unsaturated fat. CLA can exist in 28 different structures. It is found mainly in dairy and meat products.

Active research on CLA began in 1979 when researchers at University of Wisconsin studied the anti-carcinogenic properties of beef extract.  Later CLA was discovered and was famous for its anti-cancer properties. A number of research studies were conducted and it was found that CLA has body fat reducing property.

CLA image 1

Two important structures of CLA are c9t11 and t10c12. These names just describe position of double bonds in the structure. CLA exists as a ‘trans’ and ‘cis’ fatty acid. So it is technically a ‘trans’ fat but it is obtained from natural sources unlike the unhealthy industrial ‘trans’ fat.

The c9t11 isomer makes up 75-80% of CLA found in natural sources. However the t10c12 isomer is found to be biologically more active in terms of fat loss.  CLA in supplement form is not obtained from natural foods but derived by chemical alteration of vegetable oils.

How does CLA cause weight loss?

CLA exhibits body fat lowering effect in a number of ways:

  • It prevents accumulation of body fat.
  • It affects a biological target known as PPAR which regulates fat metabolism and accumulation.
  • Mitochondria are the powerhouse of the cells. CLA increases metabolism by increasing mitochondrial content of muscle cells.
  • It activates a protein called AMP- activated protein kinase which regulates fat metabolism.
  • It increases the level of uncoupling protein-1 in white fat which can cause increased energy expenditure and weight loss.
  • It causes breakdown and oxidation of fats.
  • It inhibits activity of enzyme involved in fat metabolism like lipase which adds to CLA’s body fat reducing effect.

What does science have to say about role of CLA in weight loss?

CLA is perhaps one of the highly researched weight loss supplement and we will be going through different studies to find out how helpful CLA is for weight loss.

It reduces body fat

A study that is popularly quoted when it comes to CLA’s body fat lowering effect is the one that is published in The Journal of Nutrition, 2000.  60 overweight individuals were given 1.7, 3.4, 5.1 or 6.8 g conjugated linoleic acid per day for 12 wk.

All groups lost weight but the effect was significant in high dose group. An average of 6 pound loss was observed.

A 12 week clinical trial  was conducted where volunteers received 1.7 g of CLA in milk twice daily. At the end of 12 weeks, decrease in body weight, BMI, fat mass and waist to hip ratio was observed in CLA treated group.

A Swedish study reported a decrease of 3.8% of body fat during a 3 month CLA treatment.

Research  suggests that CLA supplementation can cause decrease in body fat in specific regions such as legs and trunk region and this effect is pronounced in women. CLA supplementation is reported to decrease body fatness especially abdominal fat in obese or overweight children.

Now here is an interesting one. Researchers conducted a study  where body weight was measured during the pre-holiday season (August-October), holiday season (November-December) and post-holiday season (January-March).

It was found that compared to CLA treatment, the placebo group experienced greater weight gain during holiday season. CLA improved body composition over 6 months and body fat was significantly reduced. Researchers concluded that CLA prevents weight gain during holiday season.

A meta analysis of 18 clinical trials reveals that a dose of 3.2g of CLA per day for 6 months causes a modest loss of body fat in humans.

What does this mean?
A number of clinical trials on humans show that CLA indeed reduces body fat. This has been proven in children too. A dose up to 3.2g is found to effective for fat loss. Research proves that CLA can even prevent holiday weight gain!

It increases lean mass and influences metabolism

CLA image 2Long-term supplementation with conjugated linoleic acid (CLA) reduces body fat mass (BFM) and increases or maintains lean body mass.  A clinical trial  conducted in North Carolina reported that 12 week supplementation of 6.4g of CLA/ day resulted in an increase of 0.64 kg of lean mass in obese individuals.

Researchers conducted a study  where individuals received a very low calorie diet after which for 13 weeks they received CLA. The low calorie diet caused weight and fat loss. CLA supplementation increased regain of fat free mass which in turn increased the metabolism by 12-13%.

CLA supplementation is found to affect energy expenditure and increase utility of fat as an energy source even during sleep.

However a study  conducted in University of California, Davis 64 day supplementation of CLA (3g/day) produced no significant effect on body composition or energy expenditure.

What does this mean?
It is said that CLA supplementation can lead to weight gain in long term. However this is gain of fat free mass and muscle is a metabolically active tissue so CLA leads to increase in metabolism.

It reduces abdominal fat

Not only does CLA reduce total body fat but it also gets rid of stubborn belly fat. 25 abdominally obese individuals were recruited for a 4 week clinical trial  where they received 4.2g of CLA per day or placebo.

At the end of the study a significant decrease in abdominal circumference was seen individuals who were given CLA supplements.

CLA in combination with omega 3 fatty acids prevents abdominal fat deposition and increases muscle mass in young obese individuals.

What does this mean?
Research on humans shows that CLA supplementation for 4 weeks reduces belly fat.

It affects appetite

Animal study reports that CLA supplementation may affect genes that regulate appetite.

A study  was conducted in Netherlands where subjects were kept on a very low calorie diet for 3 weeks after which for 13 weeks they received 1.8g or 3.6g CLA or placebo every day. Appetite and food intake at breakfast next day was measured to observe whether CLA controls appetite.

Individuals lost around 7% of their initial body weight and a decrease in appetite was seen over the 13 weeks. However no reduction in energy intake at breakfast or improvement in body weight maintenance was seen.

What does this mean?
13 week treatment with CLA is found to reduce appetite but limited studies are available to validate CLA’s effect on appetite.

It works in combination with other weight loss interventions

CLA in combination with dietotherapy is found to decrease body fat by 10% and waist circumference by 6.5%.  Dietotherapy is typically altering diet and food choices to treat a disease.

Research claims that CLA in combination with proteins (whey and creatine) increases strength and muscle mass during heavy resistance training.   CLA supplementation with endurance exercise training is found to improve metabolic health.

CLA in combination with amino acid mixtures is found to increase fat burning effect of exercise.  One study states that CLA supplementation has no effect on the potential of aerobic exercise to reduce body fat or improve blood lipid levels.

What does this mean?
CLA works well with a low calorie diet to induce weight loss. It increases strength and muscle mass in response to strength training. However it does not potentiate weight loss effect of aerobic exercise.

CLA enriched foods as weight loss aids

CLA image 3In 2008, FDA approved CLA’s status as GRAS (Generally Regarded as Safe) on certain food categories such as milk, butter, cheese, nutritional bars, fruit juices etc. Therefore food companies are now able to add CLA to their products.

14 women suffering from metabolic syndrome were recruited for a study where they received strawberry jam enriched CLA along with low calorie diet.  Researchers found that CLA enriched food led to a reduction in body fat by the end of 30 days which lasted throughout the 90 day period of the trial.

Milk supplemented with 3g CLA is found to decrease body fat and waist circumference in obese individuals.

A study  conducted in France demonstrated that 98 day supplementation of CLA enriched yogurt had no effect on body composition but an increase in metabolic rate was observed.

10 fold CLA enriched butter fat produced no significant changes in metabolic health of obese individuals.

What does this mean?
Milk enriched with CLA is found to be beneficial for weight loss. However some research studies show that this is not the case with other dairy products like yogurt and butter.

Some researchers have a different view point of CLA’s anti-obesity effect

A meta analysis of 15 clinical trials  was conducted and researchers felt that CLA supplementation does not cause any clinically significant changes in body composition. Adverse events such as constipation, diarrhoea, and soft stools were reported.

A review study  investigating the safety and efficacy of CLA supplements takes into account that that CLA supplementation prevents body weight gain and fat accumulation in animal models but it reports that dietary supplements are not effective weight loss agents in humans and can cause adverse effects.

Other review studies also comment that there is insufficient data to conclude that CLA has a pronounced effect on body weight and composition.

Larsen et al report that a 3.4-g daily CLA supplementation for 1 year does not prevent weight or fat mass regain in a healthy obese population.  Similar results were obtained from an 8 week study.

A study  investigating the effect of different CLA isomers on body weight reported that a dairy drink supplemented with CLA had no significant effect on body weight.

What does this mean?
And as always there is some conflicting evidence available that states that CLA is perhaps not as effective as it is thought to be for weight loss.

Natural sources of CLA

CLA image 4The primary source of CLA is from animal products obtained from ruminants such as cow, goats, sheep etc. The CLA content of the food depends on the kind of fodder the animals get. CLA content is 300-500% higher in animal products obtained from grass fed animals than those who are fed grains.

Kangaroo meat has high concentration of CLA. Eggs are also rich in CLA. Mushrooms like ”Agaricus bisporus” and ”Agaricus blazei”, are vegetable source of CLA.

However obtaining CLA from natural sources is not such a good idea because the amount you would require to cause a clinical effect would involve consuming many calories.

Dosage

The recommended dose for CLA by research studies is somewhere between 3 to 6 grams per day. It is best to consult a doctor for the right dose and duration of treatment.

Precautions/Side effects

There are not any significant or commonly observed adverse effects reported about CLA consumption.

However some studies report negative effects on cholesterol, blood lipid profiles and increase in insulin resistance associated with large dose of CLA. Less harmful effects include gastrointestinal distress.

Therefore it is advisable to consult a doctor for the dose and feasibility of taking CLA supplements.

Conclusion

CLA ‘s body fat lowering effect seems to be quite promising as far as research is concerned. However you can’t possibly obtain it from natural sources, which is why you would have to take supplements.

Also we can’t ignore the view point of scientists who say that CLA causes only slight changes in body composition.

Also some studies do report that CLA affects the liver and causes insulin resistance. However the efficacy of supplements depends on different individuals’ body type.

As always I would again recommend you to consult a doctor before you take CLA or any other supplement. Also CLA will not change your eating habits or lifestyle. So if you are looking for something permanent, then there are no shortcuts for weight loss.

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