CLA is a particular form of dietary fat, so the obvious question here is: "How does eating fat cause you to lose fat?" Answering that question requires a closer look at the fat-free craze of the last two decades, where doctors were telling people to avoid practically all dietary fats and, instead, eat as much refined sugar and carbohydrate as they wanted. It was this sort of advice that resulted in hoards of consumers sitting around on their couches, watching TV and consuming a dozen fat-free donuts in one meal while telling themselves, "It's healthy! My doctor says I'll lose weight!"
The result of all this is the alarming rise in obesity and diabetes our population has experienced over the last two decades. Consuming unlimited quantities of sugar, refined carbohydrates and processed foods, it turns out, actually raises triglyceride levels in your blood and damages your pancreas to boot. As we now know, the body needs dietary fat, and it is the type of fat that determines the health outcome. Hence the recent distinction between "good fats" and "bad fats."
Simply put, CLA helps people lose weight because it's a good fat. Consuming it accelerates of the body's metabolic rate while slowing the body's conversion of dietary fats into body fat. In a way, when the body is getting enough fat through the diet, it doesn't feel the need to hoard fats by enlarging adipose tissue. This benefit can be further accelerated by avoiding all low-quality fats in the diet: hydrogenated oils (found in nearly all cookies, crackers and baked goods), soybean oil (the most common, cheapest vegetable oil on the market), and other low-cost vegetable oils. Instead, the consumption of healthy oils should be increased: extra virgin olive oil, flax seed oil, evening primrose oil, peanut oil, macadamia nut oil, and even extra virgin coconut oil. By consuming these oils while avoiding all refined carbohydrates, the body will naturally achieve a healthy triglyceride level in the bloodstream.
In this CLA study, it's important to note that study subjects consumed over three grams of CLA each day. That's a fairly high dose. Most people taking CLA supplements don't even come close to that dose, since many softgels hold no more than 500mg of oil. You'd have to take six or seven each day to match the dose used in the study. There's nothing wrong with that, but it's a level of supplementation that most consumers would never reach. For some reason, consumers tend to take nutritional supplements, herbs, vitamins and minerals like they were drugs: one pill a day. That's typically far less than what's needed, depending on the supplement. For example, I personally take as much as ten grams of chlorella each day -- that's twenty 500mg capsules (an entire handful). Chlorella isn't a drug, it's a superfood. People should be eating it like food. CLA falls into the same category: it's a food, not a drug. It would be more effective and more convenient to buy CLA in its liquid form and take it by the tablespoon rather than individual gelcaps.
In any case, CLA is certainly effective in helping people lose weight, but once again its effects pale in comparison to daily exercise, strength training, and the avoidance of all processed foods and metabolic disruptors. If you decide to take CLA, don't make the common mistake of thinking it replaces daily exercise. Instead, use CLA in conjunction with exercise to achieve your health and fitness goals.