~ Conjugated Linoleic Acid (CLA) Increases Metabolic Rate and Reduces Abdominal Obesity

Conjugated linoleic acid (CLA) is found in ruminant meats such as beef and lamb and in dairy products such as milk and cheese. Many studies support the anticancer, antiobesity, antidiabetic, and antiatherogenic properties of CLA (Lee et al 1994; Park et al 1997, 1999; West et al 1998; Yamasaki et al 2003).

A CLA Deficiency

CLA is essential for the transport of dietary fat into cells, where it is used to build muscle and produce energy. Fat that is not used for anabolic energy production is converted into new fat cells. New research shows how dietary CLA reduces body fat, but first let's take a look at why many Americans are now deficient in CLA, compared with their parents.

The primary dietary sources of CLA are beef and milk, and Americans are eating less beef and drinking less whole milk in order to reduce their dietary intake of saturated fat. People often drink non-fat milk, but it's the fat content of the milk that contains CLA. Since skim milk contains virtually no CLA, those seeking to lose weight by using skim milk are depriving themselves of a potential source of this fat-reducing nutrient.

Now, here's where the real problem occurs. In 1963, the CLA percentage in milk was as high as 2.81 percent. By 1992, the percentage of CLA in dairy products seldom exceeded 1 percent due to changing feeding patterns of cows. Cows that eat natural grass produce lots of CLA, while today's "efficient" feeding methods rely far less on natural grass. To illustrate, grass-fed Australian cows have three to four times as much CLA in their meat as American cows. As a result, most Americans have inadequate amounts of CLA in their diet. Here is the irony: 1) health-conscious Americans are avoiding beef and whole milk because these foods are high in fat; 2) when people do consume beef or milk, they are consuming very little CLA because of cows' altered feeding patterns; and 3) this CLA deficit may be at least partially responsible for the epidemic of overweight people of all ages that now exists.

CLA and Fat Loss

Conjugated linoleic acid (CLA) has been extensively studied for its ability to maintain lean muscle mass and promote fat loss. Researchers from North Carolina State University, Raleigh, noted CLA's mechanisms of action are still largely unknown, although it appears to modulate energy expenditure, fatty acid oxidation, lipolysis and lipogenesis. In addition, reviews have noted there is marked variation in human clinicals, often with isomer-dependent influences.

However, intervention studies using proprietary CLA compounds have shown both short-term and long-term benefits to the use of CLA on body fat mass. In a four-week trial, men taking 4.2 g/d of CLA (as Tonalin®, from Cognis Nutrition & Health) showed a significant decrease in abdominal diameter. Similar results were seen in a 12-week intervention in 60 overweight or obese subjects, who received 1.7, 3.4, 5.1 or 6.8 g/d of CLA (as Tonalin). There was a significantly higher reduction in body fat mass in the CLA groups compared to placebo, with a significant reductions reported in the 3.4 and 6.8 g/d groups. Results from a one-year study using CLA (as Tonalin) were published in the American Journal of Clinical Nutrition in early 2004. The double blind, placebo-controlled study randomized 180 men and women with a BMI of 25 to 30 into three groups to receive a placebo or 4.5 g/d of CLA (as Tonalin) in free fatty acid or triglyceride form. Researchers found a significant decrease in body fat mass in both CLA groups by as much as 9 percent; the CLA free fatty acid group also had an increase in lean body mass compared to placebo.

The results were not attributable to changes in diet or exercise, and no adverse events were reported. And in an open-label, one-year continuation of that study, researchers reported CLA supplementation helped maintain fat loss and lean body mass. Interestingly, at the end of the two-year period, CLA was also found to lower levels of leptin, promoting better sensitivity to the hormone and helping satiety.

Human clinical trials have shown reductions in body fat from CLA supplementation.
  • Supplementation with 1.8 g daily of CLA for 12 weeks reduced body fat in healthy, exercising humans of normal body weight (Thom et al 2001).
  • Men with abdominal obesity who consumed 4.2 g daily of CLA for 4 weeks decreased their abdominal diameter (Riserus et al 2001).
  • Supplementation with 3.4 or 6.8 g of CLA daily for two weeks decreased body fat mass in overweight and obese people, and the trans-10, cis-12 CLA isomer inhibited the activities of the fat-storage enzyme lipoprotein lipase (Pariza et al 2001).
  • The cis-9, trans-11 isomer, a specific isomer of CLA, increases metabolic rate and energy production (thermogenesis) (Ryder et al 2001; Brown et al 2003).
Evidence from a short-term study (12 weeks) has suggested that treatment with CLA may worsen insulin resistance (Riserus et al 2002). However, a long-term study (one year) in overweight and obese men and women has shown that CLA is effective for weight loss with no adverse effects on insulin sensitivity (Gaullier et al 2004). A 36-week toxicity study in animals given CLA at doses far exceeding those given to humans also showed CLA to be without toxicity (Scimeca 1998).

Enhancing Metabolism and Fat Burning with Guarana

Guarana is a South American shrub traditionally used by Indians to help maintain energy levels. Today, Brazilians use guarana as a health tonic. Guarana seeds contain 4 percent to 8 percent caffeine, as well as trace amounts of theophylline and theobromine. These chemicals are believed to account for guarana's energy-stimulating and fat-burning effects (Carlson et al 1998). Toxicology studies assessing guarana's effect in mice and rats demonstrated high doses of guarana (1000 to 2000 mg/kg) had no significant toxicity effects while low doses (1.2 mcg/mL) actually had an antioxidant effect (Mattei et al 1998).

In animals, guarana has been shown to increase physical endurance under stressful conditions to a greater extent than do comparable doses of caffeine or ginseng (Espinola et al 1997).

In another study, Guarana extract in an herbal formulation given to overweight human patients for 45 days was associated with an 11.2-lb weight loss in the guarana group compared with less than a 1-lb weight loss in the placebo group (Andersen et al 2001).

Guarana is well tolerated. However, adverse side effects, including heart palpitations and anxiety, have been reported when guarana is combined with powerful CNS stimulants such as ephedra and bitter orange (Citrus aurantium) (Pittler et al 2005). Therefore, guarana should not be taken in conjunction with CNS stimulants.


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