Conjugated linoleic acid (CLA) is an omega-6 polyunsaturated fatty acid found mostly in the dairy and meat of ruminant animals (think cows, sheep, goat and deer). As an essential fatty acid, CLA cannot be produced by the human body and must be obtained from other sources. Top natural sources include grass-fed beef, butter, cheese and milk.
CLA gained notoriety after several animal studies found positive results in its ability to inhibit cancer growth. Further animal studies also showed a significant improvement in body composition — as much as a 60% reduction in body fat of mice that consumed CLA. This caused a flurry of interest in CLA as a potential weight loss stimulant.
WHAT ARE CLA’S PURPORTED BENEFITS?
Proponents say CLA helps suppress the formation and inflation of fat cells and may have an effect on appetite-regulating genes in the hypothalamus — the part of the brain that controls hunger, appetite, emotion, sleep and many other essential daily functions. Other potential benefits include enhanced immunity, improved heart health and decreased risk of cancer, asthma and diabetes.
WHAT DOES THE SCIENCE SAY?
While the initial animal studies were promising, human studies have not proven to be so successful, nor quite so clear. One study in the American Journal of Clinical Nutrition looked at 18 long-term studies where participants took CLA supplements for durations ranging from six months up to two years. Overall, the group taking CLA lost more weight than those on the placebo, but the average weight loss was less than a pound per month.
There’s also discrepancy on which type of CLA promotes potential weight loss. CLA is an umbrella term for several different isomers (more than twenty) that have very similar chemical structures.
Most CLA products are a combination of two different isomers (100% pure CLA is not available on the market). As reported in a comprehensive review published in the Journal of Nutrition and Metabolism, one form (10-CLA) tends to show positive effects on fat metabolism while combinations of two other CLAs inhibit cancer cells. Another meta-analysis from the European Journal of Nutrition found CLA-focused-studies not only had a wide range of dosages, but the amount of CLA taken wasn’t related to the amount of change in body composition. In other words, more CLA did not equal more weight loss, if any at all.
Overall, the magnitude of the effects were small and clinical relevance remains uncertain. Some forms of CLA have even reported adverse effects with supplementation, such as oxidative stress, insulin resistance, inflammation and gastrointestinal irritation.
THE BOTTOM LINE
While natural whole food sources of CLA like grass-fed beef, butter, milk and cheese can certainly be part of a healthy well-balanced diet, they have miniscule amounts of CLA in relation to the doses that were used in both the animal and human clinical trials. Moreover, while supplements are more concentrated than natural sources, they aren’t regulated and can be packaged and co-formulated with other ingredients.
There are a lot of uncertainties around CLA. We don’t know how much is effective (if at all), we don’t know how long we should take it to reap any sort of benefit, and we don’t know which type is best, either. Many of the benefits are not well documented or supported and long-term effects are unknown.
Ultimately, it’s better to work toward your weight loss goals with more proven strategies. Keep a sound focus on a well-rounded diet, develop a solid physical activity regimen, improve your sleeping habits and practice self-care. Don’t get upset if you veer off track, just remind yourself consistency beats perfection for weight loss.
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