Conjugated linoleic acid, referred to as CLA, is a type of polyunsaturated fatty acid that is often used as a weight loss supplement.

CLA is found naturally in foods like beef and dairy. The type found in supplements is made by chemically altering a fat found in safflower oil.

Safflower oil supplements have been promoted as an easy way to blast stubborn belly fat and curb appetite. They’ve even been featured on hit TV shows like Dr. Oz.

Some people believe that safflower oil itself is a good source of CLA, and increase their intake of this vegetable oil to lose weight.

This article explains the differences between naturally occurring CLA and its supplement form, and why consuming more safflower oil may not be a good idea.

CLA Safflower Oil

CLA is a type of trans fat naturally found in certain foods. It can also be made by chemically altering the linoleic acid found in vegetable oils.

The CLA found in foods like grass-fed beef and dairy is not the same as the type derived from vegetable oil.

Commercially made CLA (found in supplements) has a different fatty acid profile than natural CLA and is much higher in trans-10 and cis-12 fatty acids (1).

Although CLA derived from vegetable oil has been linked with weight loss in some studies, the results are underwhelming.

For example, a review of 18 studies showed that people who supplemented with vegetable oil-derived CLA lost only 0.11 pounds (0.05 kg) per week, compared to a placebo group (2).

Similarly, another review found that doses of CLA, ranging from 2–6 grams over 6–12 months, led to an average weight loss of only 2.93 pounds (1.33 kg) (3).

Even though they are promoted for their ability to melt belly fat, a recent review found that CLA supplements failed to reduce waist circumference in men and women (4).

Another study demonstrated that taking 3.2 grams of CLA supplements per day for 8 weeks had no effect on body fat reduction, including belly fat, in young obese women (5).

What’s more, studies have linked CLA supplements with several adverse effects.

Large doses of CLA, such as the amount provided in supplements, have been linked to insulin resistance, decreased HDL, increased inflammation, intestinal upset and increased liver fat ( 6, 7).

Though this supplement may have a measly effect on weight loss, the scientific community is skeptical (8).

Summary CLA is found naturally in certain foods or chemically derived from vegetable oil. It has little effect on weight loss and has been linked with several adverse effects.

Many people think that safflower oil is a good source of CLA. However, safflower oil only contains a minuscule .7 mg of CLA per gram (9).

Over 70% of safflower oil is composed of linoleic acid, a type of polyunsaturated omega-6 fatty acid (10).

Linoleic acid can be converted into a form of CLA that is used to make concentrated supplements.

Many people assume that CLA safflower oil supplements are just safflower oil in pill form.

Yet, CLA safflower oil supplements that you see on the shelf have been chemically altered to contain a high amount of CLA, usually over 80%.

Summary Safflower oil is a poor source of CLA and needs to be chemically altered in a lab to produce the form sold in supplements.

Safflower oil is rich in omega-6 fats and devoid of omega-3 fats.

Although your body needs both in order to function and thrive, most people take in much more omega-6 fatty acids than omega-3s.

The typical Western diet is estimated to contain as much as 20 times more omega-6s than omega-3s due to high amounts of refined vegetable oils and processed foods (11).

For reference, the ratio of omega-6s to omega-3s in a traditional hunter-gatherer diet is closer to 1:1 (12).

Diets high in omega-3 fats have been linked with lower incidences of diabetes, heart disease, dementia and obesity, while diets high in omega-6 fats have been shown to increase the risk of these diseases (13, 14, 15, 16).

Though safflower oil is promoted as a way to blast fat and help with weight loss, vegetable oils rich in omega-6s are already consumed in excess, with little benefit for your waistline.

Consuming more omega-6-rich oils, like safflower oil, actually increases obesity risk (17).

Summary Safflower oil is high in omega-6 fats, which most people already consume in excess. Having too many omega-6s and not enough omega-3s in your diet can be harmful to overall health.

While safflower oil is not the same as safflower CLA supplements, some evidence suggests that safflower oil may be effective for reducing belly fat.

Nevertheless, research is extremely limited in this area (18).

In one study, 35 obese women with diabetes received 8 grams of safflower oil or CLA in pill form for 36 weeks.

At the end of the study, the group that consumed the safflower oil pills experienced a significant loss in belly fat compared to the CLA group.

However, the safflower oil significantly increased AST, an enzyme that indicates liver damage when elevated.

This is important, as several studies have found that feeding rats safflower oil-rich diets increased the accumulation of fat in their livers (19, 20).

Also, although the safflower oil group experienced a reduction in belly fat, they had no change in BMI or total fat tissue. This suggests that consuming safflower oil caused belly fat to be deposited in other areas of the body.

Much more research needs to be conducted to determine if supplementing with safflower oil is a safe and effective way to boost weight loss.

For now, evidence suggests that a disproportionate balance of omega-6 fats to omega-3s is detrimental to overall health.

This knowledge, combined with the lack of evidence that it benefits weight loss, is a good reason to limit safflower oil in your diet.

Summary More research is needed to determine the safety and effectiveness of using safflower oil to promote fat loss.

Although safflower oil is not a good choice for weight loss, increasing the amount of other, healthier fats in your diet is.

Foods rich in anti-inflammatory omega-3 fats like salmon, walnuts, chia seeds, flax, hemp and egg yolks can benefit your health in many ways.

For example, a 25-year study of over 4,000 people found that those who ate more foods rich in omega-3s had lower incidences of metabolic syndrome, including less belly fat (21).

Plus, a diet rich in omega-3s has been associated with benefits such as a lower risk of chronic diseases like heart disease and diabetes (22).

Consuming omega-3 fatty acids from foods or supplements has also been linked to a decrease in overall mortality (23).

What’s more, choosing foods rich in omega-3s over vegetable oils full of omega-6s provides your body with much more nutrition.

For example, one ounce of walnuts delivers over 20 different vitamins and minerals including magnesium, B vitamins and potassium (24).

An equal amount of safflower oil is poor in nutrients, only providing a good source of vitamin E and K (25).

Summary If you want to lose weight, it's best to focus on healthy fats. Consuming foods rich in omega-3s may benefit weight loss and improve overall health.

Safflower oil is a type of vegetable oil that is chemically altered to produce CLA supplements.

However, safflower oil itself is very low in CLA and high in omega-6 fats, which, in excess, aren't good for your health.

Although supplementing with CLA may promote a very small amount of weight loss, the evidence supporting the use of safflower oil for fat loss is weak.

If you want to lose weight and keep it off, skip the supplements and instead focus on the tried and true methods of increasing activity and consuming healthy, nourishing foods.