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CLA & Weight Management: Will it help?

by Jeff Thiboutot MS, CN

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It has been nearly a year since Matt and I completed SPEED. We recommended some weight loss supplements that we thought had enough evidence and real life applicability. To make sure that our recommendations are sound, Matt and I continually re-evaluate the evidence for our recommendations. One supplement that we did not recommend at the time was CLA. Based on some additional information I have come across since the publication of SPEED and a discussion with a professional acquaintance, I thought I would re-examine CLA for its ability to help with losing weight and keeping it off.

Here is the basic conclusion for those of you with a short attention span; from my extensive re-evaluation of the evidence CLA will help to reduce body fat, particularly in the midsection, and may help to preserve lean tissue, but its effects are so minor that the real world significance is very poor (it will cost about $42 to lose an additional 1.1 pounds a month). This means that the cost of the supplement, for most people, is not justified by the results it will produce. To learn more on how I came to that conclusion keep reading.

Conjugated linoleic acid (CLA) is a fatty acid that has received a lot of attention over that past couple of decades. This is due to the fact that many animal studies and some human studies have shown that this type of fat can have anticarcinogenic, antiathergenic, antidiabetogenic and anti-inflammatory properties (Bhattacharya et al; Huang et al). The potential for these effects are promising but have still not been clearly demonstrated in human trials (Benjamin & Spencer; Huang et al; Smedman & Vessby). Additionally, there is some potential for negative effects with higher amounts, particularly the t10 c12 form (more on that latter). The other main focus of research with CLA has been on fat loss which is what the focus of this paper will be.

CLA is found in animal products, particularly dairy and meats. The amount of CLA found in these products will vary depending on what the animals eat. The CLA content will typically be higher from cows that are feed grass verses grains (Daley, et al). People eating a fair amount of these products are likely to ingest about 650 grams of CLA a day (Larsen). The average American ingests about 150 to 200 mg/day. (Daley et al).

An additional aspect related to this discussion is the different isomers (types) of CLA that are typically ingested. CLA is actually a general term that refers 25 different, but related isomers of fat (Benjamin & Spencer; Huang et al). The type of CLA that is most commonly found in foods is t9c12 (rumenic acid) which typically makes up about 90%, while the t10c12 typically makes up a very small percentage (Daley et al). This fact is important because the different types (isomers) have different biological actions/affects.

When it comes to health benefits, it seems that the t9c12 form is the type of CLA that causes the beneficial effects (Bhattacharya et al). When it comes to weight management aspects, it seems that the t10c12 form is causing most of the changes (Bhattacharya et al; Wang et al). However, the evidence in humans is still not as solid as the evidence in animals (Benjamin). As alluded to earlier, there is some concern that the t10c12 form can actually have negative health effects, such as reducing insulin sensitivity, increasing C – reactive protein, and causing fat to be deposited in the liver and spleen (Benjamin; Larsen; Wang). Like most of the research on CLA, most of these affects are found in animal models, but there are some human studies demonstrating these effects (Riserus; Larsen). The evidence for negative effects is not crystal clear, but there seems to be enough evidence for concern and the potential negatives must be considered when looking at the potential positives.

Now that some background information on the topic has been covered, I will now focus on the weight management aspects. The first things that will be covered are four recent reviews on CLA and weight loss. Second, some of the specific studies will be elaborated upon. Third, the potential for long-term weight management benefits will be discussed and then finally a conclusion.

There are four in-depth reviews on CLA that I have found. Here are the conclusions of each one, starting from the oldest one.

In Larsen et al (2003), the authors conclude “although CLA appears to attenuate increases in bodyweight and body fat in several animal models, CLA isomers sold as dietary supplements are not effective as weight loss agents in humans and may actually have adverse effects on human health.” (p.2234)

In Wang and Jones (2004), the authors stated “The results of human clinical studies on the effects of CLA on body weight and composition are inconsistent…Other studies did not show any effect of CLA (.7-6.8g/d) on body weight in healthy obese or nonobese men and women. [However] Reduction in body fat was observed in some human trials involving CLA supplementation…It should be noted that the reduction of fat mass by CLA supplementation is much less in humans than in animals and that there is no dose response of CLA observed about its effect on human fat mass.” (p.1156s)

In Bhattacharya et al (2006), the authors concluded “In summary, some short and long-term studies in healthy and obese, sedentary and exercised humans have indicated the beneficial effects of CLA in reducing fat mass without significantly affecting bodyweight. However, the dramatic effects seen in animal studies, especially in mice, have not been reflected in human studies. This may be partly because CLA dosage used in human studies is much lower than doses used in animal studies. Moreover, most animal studies have been in young growing mice or rats, whereas studies in humans were mostly in mature volunteers…More human trials in large groups of subjects, both in adolescents and adults, are urgently needed before CLA isomer mixture or individual isomers can be recommended for improving body composition, especially in reducing fat mass in humans.”(p.792)

The most recent review by Whigham et al (2007) stated, “In conclusion, when the body of evidence is considered as a whole, CLA does have a beneficial effect on human body composition. Although this effect is modest, it could be important if accumulated over time, especially in an environment where continuous, gradual weight gain is the norm in the adult population.” (p.1209)

From looking just at these reviews one could conclude that the balance of evidence shows a positive effect of CLA on body composition. Interestingly, the first review by Larsen et al (2003) came to a much different conclusion. Before getting too excited about the positive reviews, I think it is important to highlight what the actual changes were for those supplementing with CLA. It is important to answer the following question: Does supplementing with CLA actually make a real-world difference? Also, what is the financial cost to obtain these kinds of results?

While reviewing a number of the CLA studies with humans, it became clear that the effects, if there were some, were very small. The following chart displays the amount of weight or fat loss attributed to CLA. As you can see (chart 1), the typical amount of extra weight lost from using CLA is very small.

Chart 1CLA studies that showed a benefit of weight or body fat reduction
Study Length of study # of participants Dosage (grams) of CLA per day Average weight/fat lossPer week
Blankson et al (2000) 12 wk 47 overweight/obesemale & female 5 groups1.7, 3.4, 5.1, 6.8 - .32 lbs wtBest results was from the 3.4 g group
Riserus et al (2002) 12 wk 60obese men 3.4 -.03 lbs wt
Gaullier et al (2004) 1 year 180BMI 25-30

male and female

3.8 - .10 lbs of fat mass
Gaullier et al (2005) 2 years 134male & female 3.4 - .06 lbs of fat mass
Sahin et al (2008) 8 wk 20BMI > 25

only females

1.8 - .87 lbs wt*
*No control group

The following chart displays the studies that showed no benefit from CLA supplementation.

Chart 2CLA studies that showed NO benefit of weight or body fat reduction
Study Length of study # of participants Dosage (grams) of CLA per day Average weight/fat lossPer week
Zambell et al (2000)* 64 days 17female

mean BMI 23

3 NO statistical difference between CLA and control group
Riserus et al (2001) 4 wk 25abdominally obese men 4.2 NO statistical difference between CLA and control group
Smedman et al (2001) 12 wk 53BMI 19-34.5

male & female

4.2 Borderline statistical significance in body fat change. However, BMI, body weight, waist-to-hip ratio, and sagittal abdominal diameter were unchanged
Larsen et al (2006) 1 yr 101BMI > 28

male & female

3.4 After 1 yr, no significant difference in body weight or body fat regain was observed between treatment groups
*Metabolic ward study

A few things about the above studies need elaboration. First, only the Zambell et al study was a metabolic ward study. This is the only study that tightly controlled energy intake and activity levels. All of the other studies recommended that participants maintain their diet and activity levels and had the participants fill out some amount of diet journals. This method is common and easier to administer, but lacks the rigorous control of a metabolic ward study. Regarding the Zambell et al study, even though it was small, the high level of control substantially increases the quality of results. As shown above, the Zambell study found NO statistical difference between the CLA and control group. The second thing to point out is the lack of a control group in the Sahin et al study. The lack of a control group significantly decreases the quality of results. This is important because this study actually showed the best results. But, again, the results have to be viewed in the context of no control group and, like the other studies; it had relatively poor diet and activity control.

The final topic to discuss is the ability of CLA to help maintain weight loss. There are two particular studies that looked at this affect. First the Kamphusi et al (2003) paper concluded;

…13 weeks supplementation with 1.8 or 3.6 g CLA/day after a 3-week VLCD was not effective in improving body weight maintenance after weight loss compared to placebo…CLA lowered regain of %body fat by increasing regain of fat-free mass, and consequently increased the resting metabolic rate (p.846).

The second paper on this topic by Larsen et al (2006) concluded;

… 1-y supplementation with a mixture of CLA isomers (3.4g/day) has no clinically important effect on body weight and body fat regain after an 8-wk LCD-induced weight loss in obese persons (p.612).

Based on these two studies, when it comes to maintaining weight loss, CLA is not very helpful.

With all of the information presented above, the final question is; does the use of CLA have a real world benefit for weight management can now be answered. It does seem that CLA will often increase lean mass, although a relatively small amount, and will decrease fat mass, particularly in the midsection, but again, a very small amount. But will the changes really help the typical person trying to lose weight? For contextual purposes, let’s say that the average person trying to lose weight wants to lose thirty pounds. Also, for the monetary aspect, based on the price of a bottle of CLA ($32 for 90, 1000mg capsules from Designs for Health), a daily intake of 4 grams (this should be a sufficient dosage based on the previous studies, see chart 1) of CLA will cost $1.40 day. This would equal about $42/month. Therefore, it would cost $42 to lose an additional 1.1 pounds (the average weight loss from the 5 studies showing a positive result). Is losing an additional pound of fat per month worth 42 bucks? Could this money be spent on other weight related supplements that would produce better results?  Could the money be spent on higher quality foods, like grass-fed dairy products or maybe a gym membership? This is an individual choice, but for most people there is a finite amount of money that can be spent on food and supplements.

Additionally, some may argue for the lean tissue benefit. Yes there is some benefit regarding preservation of lean tissue, but there are better alternatives for getting this result. For instance, a low carbohydrate diet with moderate protein and some exercise, particularly resistance training can often maintain lean tissue during a weight loss diet (Layman et al; Stiegler et al; Volek et al). While on this subject I think it is important to point out that there seems to be an excessive concern over lean tissue maintenance. Yes, lean tissue is very important for health and contributes to BMR (Wolfe). However, the real metabolic impact of a few pounds of lean tissue gained or lost is minor when it comes to BMR (Wolfe, R). For a more in-depth explanation of this topic see my article, The Muscle Metabolism Myth available here. Also, in general, when people gain weight they typically gain some muscle as well as fat (Bouchard et al; Diaz et al, Pasquet et al).  In fact, the cumulative evidence from many overfeeding experiments shows that 30-40% of the weight gained is made up of fat-free mass (Joosen & Westerterp). Therefore, is it really a big deal if people lose a few pounds of lean tissue during the weight loss process? Yes, it would be best if they didn’t, but is it really that bad? As mentioned before, doing a bit of resistance training and following a good low carbohydrate diet will often preserve lean tissue and in some cases this approach has actually increased lean tissue during weight loss (Volek et al).

After looking at the evidence and considering the real world benefit, I conclude, if you have an extra 40 bucks or so go ahead and take CLA, but don’t expect any great body changes from using it.

The material presented is for information purposes only. The information presented is not intended as medical advice, nor to replace the advice of a physician or other health care professional. Anyone wishing to embark on any dietary, drug, exercise or lifestyle change for the purpose of preventing or treating a disease or health condition should first consult with, and seek clearance and guidance from a competent health care professional.

The decision to utilize any information presented is ultimately at the sole discretion of the reader, who assumes full responsibility for any and all consequences arising from such a decision. The authors and Reason Productions LLC shall remain free of any fault, liability or responsibility for any loss or harm, whether real or perceived, resulting from use of the information in this presentation.


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