The effects of conjugated linoleic acid (CLA) in combination with resistance training
The effects of conjugated linoleic acid (CLA) in combination with resistance training
This article is a summary of an interesting study published some time ago that examined the effects of conjugated linoleic acid(CLA) in conjunction with resistance training on the human body. This study is interesting because despite the fact that CLA has been used by countless bodybuilders and fitness athletes for over a decade, there have only been 2 studies looking at the interaction of CLA and training.
What is conjugated linoleic acid (CLA)?
Before we get to the actual study, here is a brief summary of conjugated linoleic acid to help bring all readers up to the same level of knowledge.
Conjugated linoleic acid (CLA) is a supplement designed to increase metabolic rate and fat utilization, and through the combination of these two effects, should result in weight loss. CLA is naturally found primarily in dairy products - but not in low-fat dairy products - and meat, particularly beef and lamb. The typical dietary intake is between 150 and 200 mg of CLA per day, while the usual dosage when using a CLA supplement is 3 to 5 grams per day, which is 20 to 40 times higher than the normal dietary intake.
Although CLA is a popular fat loss product, there is only a limited amount of scientific research to support its use. About half of these studies show that CLA can effectively support fat loss, while the other half show the opposite. If you are a rat, a cow or a pig, then CLA is likely to be quite effective for fat loss, while studies conducted with humans have not been particularly promising.
In this context, it should perhaps be mentioned that there are different forms of CLA, known as isomers, which have the same chemical formula but different structures. It could be that different isomers of CLA have different effects and could therefore produce different results.
The following study, published in the February 2006 issue of the Medicine and Science in Sports and Exercise Journal, examined the effects of CLA supplementation in conjunction with resistance training. The interesting thing about this study is that it was conducted with human subjects and therefore the question of whether the results are transferable to humans does not arise, as is the case with animal studies.
The effects of conjugated linoleic acid supplementation during resistance training
Craig Pinkoski, et al, Medicine and Science in Sports and Exercise, issue 38 (2), pages 339-348, 2006
The largest previous human study lasted 1 year and showed that CLA supplementation over this period reduced body fat mass in overweight subjects while slightly increasing lean body mass. Two other studies combined CLA with training and one of these studies showed that CLA was effective in reducing body fat, while the other found no changes in body composition.
So basically, we don't know anything about training and CLA. Furthermore, it's important to point out that the type of training in the two studies wasn't even specified, meaning it could have been anything from powerlifting to ballet.
Basically, this fact cries out for well-designed studies to be conducted to determine the true effects of CLA in combination with an exercise program. And that was exactly the purpose of this study - to determine the effects of CLA supplementation during a resistance training program.
The authors hypothesized that CLA, when combined with resistance training, would increase lean body mass and strength gains, reduce fat mass, increase resting metabolic rate, increase fat oxidation, and reduce urinary markers of muscle and bone loss compared to resistance training without CLA.
The subjects
This placebo-controlled, double-blind study involved 85 healthy men and women aged 18 to 45 years. All subjects were physically active at the time of the study, which is important as novice exercisers tend to achieve faster and greater results at the start of exercise.
The study lasted for a period of 7 weeks and included a periodized resistance training program that all subjects followed. The following variables were taken into account when evaluating the study:
- Body weight
- Body fat percentage
- Fat-free body mass
- Fat mass
- Strength
- Maximum torque during leg extension
- Muscle thickness
- Metabolic rate at rest
- Respiratory exchange ratio
- And some more...
In this article, only the variables that are important for this review of the study are considered.
The training program
The resistance training program consisted of 12 exercises chosen to work all major muscle groups. For each exercise, 3 to 4 sets of 4 to 10 repetitions were performed three times a week with approximately 75 to 90% of the maximum weight for one repetition (1RM weight). Basically, this was a fairly intensive training program.
To measure body composition, the scientists used a measuring device known as the Body Pod, which is more reliable than most other methods of determining body composition.
Maximum strength was determined using bench presses and squats.
After the actual study was completed, another study was conducted with a subset of the original 85 study participants. This follow-up study was a crossover study, meaning that the subjects switched groups after a break to ensure that all CLA had left the body. Subjects who were previously in the CLA group switched to the placebo group and subjects from the placebo group switched to the CLA group.
Results
A significant increase in lean body mass was observed in all male subjects, while no corresponding change was observed in women. However, no differences in total body mass were observed between the CLA and placebo groups over the course of the study.
However, there was a greater increase in lean body mass and a greater reduction in fat mass and body fat percentage in the CLA group compared to the placebo group. There was no significant difference between the CLA group and the placebo group in terms of average changes in body strength.
During the seven-week follow-up study, an increase in body mass, fat mass and body fat percentage was observed in the subjects in the placebo group, while no such increases were observed in the subjects in the CLA group.
It should also be mentioned at this point that there were no differences between the CLA group and the placebo group in terms of observed side effects, which is an indicator that CLA does not appear to have any significant side effects.
Conclusions
The main results of the seven-week study were that a significant increase in lean body mass and a reduction in body fat mass was observed in the CLA group. The authors noted that these changes, although significant, were relatively small in absolute terms, which calls into question their clinical relevance.
Nevertheless, the results are very interesting as this study is one of the few human studies to look at the relationship between CLA and resistance training. Longer studies are urgently needed to see if the trend seen in short studies is maintained over a longer period of time.