Conjugated linoleic acid (CLA) and weight loss?


I am trying fairly unsuccessfully to lose weight. I think I gained weight as a result of taking Paxil. Now that I am Paxil-free, I am looking for something to help me lose weight. What do you know about CLA (conjugated linoleic acid)? It seems like it should help. Do you know anything about it? Are there any side effects? Is it beneficial?


Dear Reader,

Linoleic acid is the fatty acid under which the omega-6 fatty acids, a type of “good fat”, are categorized. Conjugated linoleic acid (CLA), on the other hand, has the same molecular formula as linoleic acid but a different chemical structure. These essential nutrients aren’t produced by the human body and therefore must be ingested from plant- and animal-based food products, such as vegetable oils, dairy, and beef products. As you’ve noticed, CLA is advertised as a dietary supplement for weight loss; however, it’s unclear how effective CLA is for this purpose. Additionally, there are some risks associated with it, so it's great that you're doing your homework! All that said, there are still ways that you can work towards healthy and safe weight loss through a variety of lifestyle behaviors.

In nature, CLA is formed by bacteria that live within the digestive tract of grazing animals, such as cows. When these bacteria encounter linoleic acid, they make small structural changes to create the conjugated form, CLA. It’s critical to know that different CLA sources don't contain the same form of the compound; CLA c9t11 is more common in food sources whereas supplement sources tend to have CLA t10c12. Humans take in CLA through consumption of meat and dairy products or altered vegetable oils, though the amount in foods is much less than in supplements. Keep in mind that humans ingest enough "beneficial" fats through balanced diets to reap the health benefits, so it’s good to consider how much you’re already getting through diet before turning to supplements.

Some studies have found that CLA t10c12 may help prevent ovarian cancer and have anti-inflammatory effects, while c9t11 can help treat psychiatric conditions. Studies have found that both can inhibit tumor growth and improve bone metabolism. Other studies indicate that CLA c9t11 supplements may lead to nausea, stomach pain, gas, diarrhea, accumulation of fat in the liver, inflammation, increased insulin resistance, and lower HDL ("good") cholesterol. The negative effects have been confirmed in multiple studies over the years, while the research on the positive effects is much more recent and limited. In terms of weight loss claims specifically, the testing of CLA supplements has been based largely on animal studies, which have resulted in a combination of fat loss and muscle gain. As for human studies, the results haven’t been nearly as positive or consistent and have largely only been conducted with overweight males. While some studies have yielded the desired result of fat loss, others showed negligible changes, or even increased fat mass. In addition to conflicting research conclusions, the quality of many of the human studies has been called into question. Ultimately, there isn't enough conclusive evidence to say that CLA (be it t10c12 or c9t11) can lead to weight loss.

It’s also worth noting that the U.S. Food and Drug Administration (FDA) doesn't test these products to verify the claims listed on manufacturers' labels. Given that, neither the FDA nor the product's manufacturers need to prove that the product is effective or even safe to take. At this point in time, the available research leaves questions as to whether long-term use of CLA supplements by humans is safe. Additionally, many products don't note what type of CLA their supplement contains. Therefore, it’s recommended that folks are cautious when using CLA supplements, and those who are pregnant or lactating are advised to avoid taking them altogether.

Despite the research on CLA, there isn’t enough conclusive evidence to guarantee its effectiveness and long-term safety. Tested and true methods for weight loss include sustained lifestyle changes, such as a moderate reduction in calorie intake and increased physical activity. These weight loss strategies have been proven to be safe for many and may also raise your energy level, help to relieve stress, and decrease risk of chronic disease. Since you've had a hard time losing weight on your own, you may also want to enlist the help of a health care provider, registered dietitian (try searching through the Academy of Nutrition and Dietetics website), or a personal trainer. These specialists will work with you to achieve your health goals by helping you to identify and manage nutrition and fitness challenges. You can also read more about these strategies on your own in the Go Ask Alice! Nutrition & Physical Activity archives.

Hope this helps!

Last updated Feb 23, 2018
Originally published Jun 03, 2005

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