What is CLA? – Great for Fat Loss -or- A Big Fat Lie?

CLA is short for Conjugated Linoleic Acid. It is produced naturally in products such as meat, cheese, and dairy. The CLA found in these products is at such low levels you are unlikely to see any effects from these sources. Many people turn to supplementing their diet with CLA in hopes to lose fat mass without sacrificing lean body mass or muscle. This is just one of the many reported benefits of CLA.

The scope of this article will go into detail about some of these claims and the research conducted behind them. It is out of the scope of this article to cover all research studies conducted on CLA. I will do my best to cover enough to inform you as the consumer to things you should be aware of when it comes to CLA.

Claims for CLA

CLA was discovered in fried hamburger meat of all places in the 1970’s. The scientist that discovered claimed it shrunk the size of tumors in lab rats. This stirred up a frenzy of debate and many scientific studies were soon being conducted. Claims started to become widespread about what CLA was capable of.

Here are just a few I came across from a quick Google search.

“Some of the most known suggested benefits of CLA supplementation include:

Increased metabolic rate: This would obviously be a positive benefit for any type of athlete that is trying to lose weight and improve body composition.

Enhanced muscle growth: Muscle burns fat, which also contributes to increased metabolism, which is useful in weight loss and management.

Lowers cholesterol and triglycerides: Since many people these days have elevated cholesterol and triglyceride levels, even with treatment, this benefit can have an impact on any person who has high cholesterol.

Lowers insulin resistance: Lowering insulin resistance has been shown to help prevent adult-onset diabetes and make it easier to control weight.

Reduces food-induced allergic reactions: Since food allergies can be at play when weight loss becomes difficult, this can be of help.

Enhances immune system: With the variety of bacteria and poor immune systems in contemporary society, enhancing the immune system’s ability to function properly is a positive benefit to all.”

-Mike Hajoway, bodybuilding.com



-Reform Mag, bodybuilding.com

Those are some pretty big claims. Let’s dig a little deeper into what’s going on here.

Claim #1 & #2:

CLA will increase your metabolic rate and improve muscle growth.

This is how CLA is primarily marketed. This gives people the impression CLA makes a great weight-loss supplement without sacrificing lean body mass.

According to a research study conducted by Kamphuis MM & Associates this may not be the whole story. They conducted a study published in International Journal of Obesity and Metabolic Related Disorders which lasted over the course of 13 weeks. The subjects were 26 overweight men and 28 overweight women with an average BMI of 27.8. They were all placed on a very low-calorie diet. As expected, this decreased %body fat, fat mass, fat-free mass, resting metabolic rate, respiratory quotient and plasma glucose, insulin, and triacylglycerol concentrations.

After the weight loss, the subjects were then given a CLA supplement for 13 weeks. The participants did regain fat-free mass (muscle) when compared to a placebo which would attributed to the increased metabolic rate but…

“CLA did not affect %body weight regain (when compared to the placebo)… It did not result in improved body weight maintenance after weight loss.” -Study Authors

Another study published in the American Journal of Clinical Nutrition has shown that CLA in doses of 3.2 grams per day can produce modest loss of fat in humans. (on average .1 – .05 kg per week.) 

What this means is it may improve lean body mass which in effect will increase your metabolism. Some studies have also shown it might, on average, produce limited results as a fat-loss supplement.

That doesn’t mean CLA is effective as a weight loss supplement, but overall could be better at preserving lean body mass while dieting.

Claim #3

CLA affects blood cholesterol and triglyceride levels. 


CLA, structurally, should be considered a trans fatty acid. Increased intake of trans-fatty acids is linked to increased risk of cardiovascular disease. This mean CLA could possibly have adverse effects on blood cholesterol levels. More research is required to evaluate these claims. This is according to The Journal of Lipid Research.

What’s more, if you take too much CLA it may actually decrease your HDL (good) cholesterol. These are finding published in The Journal of Nutrition. 

Claim #4

CLA decreases insulin resistance.

I’ll just leave a quote here from the American Diabetes Association

Unexpectedly,t10c12 CLA increased insulin resistance (19%; P < 0.01) and glycemia (4%; P < 0.001) and reduced HDL (good) cholesterol (−4%; P < 0.01) compared with placebo, whereas body fat, sagittal abdominal diameter, and weight decreased versus baseline, but the difference was not significantly different from placebo. The CLA mixture did not change glucose metabolism, body composition, or weight compared with placebo but lowered HDL cholesterol (−2%; P < 0.05).

Depending on your source of CLA you could be making your insulin sensitivity worse. Understand the CLA source before purchasing.

Claim #5

CLA can reduce food allergies.

I can find no research-based evidence whatsoever to this claim.

Claim #6

CLA will improve your immune system. 

According to a study published in the European Journal of Clinical Nutrition CLA can improve the immune response in young healthy adults. More studies are currently being conducted to prove the validity of this claim.


In Conclusion

It’s important to note that most of the benefits associated with CLA have only been found in animal studies. It has undergone somewhat limited research in human trials. What’s more is most of the trails conducted on animals would equate to a dosing of about 130 grams per day for humans. This is an extremely high amount of fat to be consumed daily. To consume this amount also puts you at increased risk of liver hypertrophy and increase insulin resistance according to a report by The Journal of Lipid Research.

If you only read one thing…

Although there is some promising research investigating CLA especially when it comes to promoting lean body mass while dieting, I just want to note one last study conducted by the National Strength and Conditioning Association (NSCA). If you’re not aware, the NSCA is one of the nation’s top sports research and certifying agencies for professional coaches and trainers. They have shown that CLA could possibly increase oxidative stress in endurance athletes. The NSCA is quoted in their study…

“We suggest that endurance athletes and those looking to improve their own skeletal muscle mass refrain from CLA supplementation, because it seems to intensify the oxidative stress caused by exhaustive exercise.”

Based on this study alone I feel I cannot ethically or morally recommend this supplement. It’s findings in human trials are too vague and limited to prove it’s worth taking. There also appears to be too many contraindications to our fitness to even recommended as effective.

That being said, if you decide CLA is the right supplement for you, it’s important to weight the pros and cons before purchasing. As with all supplements, it’s important to speak to your doctor and go over all your medications.

Be sure to check out all of Jeff smith fitness Supplement Reviews. Find out which ones are right for you and your fitness goals.

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