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Healthnotes Newswire (July 26, 2007)—According to a new meta-analysis, conjugated linoleic acid (CLA) may cause modest, short-term loss of body fat in certain people, but unanswered questions about the safety of long-term use indicate that it’s premature to embrace it as the new go-to supplement for weight loss. 

CLA is a fatty acid that has been shown to reduce body fat in animals, although its effect on human body fat has been unclear. The meta-analysis, published in the American Journal of Clinical Nutrition, reviewed 18 studies, in order to determine whether supplementing with CLA reduces human body fat.

Results showed that people supplementing with an average of 3.2 grams per day of CLA lost a modest but significant amount of body fat: about 0.2 pounds per week compared with those people who took placebo (olive or safflower oil in most studies).

But the meta-analysis had its limitations: studies reviewed were of short duration (making the long-term effects of CLA unclear), and included other interventions, such as diet and exercise, that potentially contributed to weight loss, thereby calling the study results into question. The authors also state that it is unclear how much CLA a person has to take during what length of time to achieve optimal body fat loss. They concluded that it is not possible to draw conclusions about the effects of CLA on long-term weight maintenance.

CLA has several different chemical structures (called isomers), and certain isomers may be more effective in reducing body fat in humans than other isomers, as has proven true in animal studies, but further research is needed. The authors report that CLA was not associated with severe adverse effects in the studies they reviewed but there have been reports of CLA adversely affecting several risk factors for chronic disease.

“In clinical trials, supplementation with CLA has produced various unwanted effects, including increases in serum cholesterol levels, insulin resistance, and markers of inflammation. Additional research is needed regarding long-term safety of CLA before its routine use can be recommended,” said Healthnotes Chief Science Editor Alan Gaby, MD, an expert in medical nutrition.

People who are overweight or obese often turn to supplements such as CLA in hopes of losing weight or maintaining a healthy weight after weight loss. Healthcare professionals advise that it is important to understand the risks and benefits of dietary supplements and often recommend instead that people looking for safe, long-term weight loss focus primarily on modifying lifestyle behaviors such as diet and exercise.

(Am J Clin Nutr 2007;85:1203–11)

Healthnotes Newswire (March 27, 2008)—Many postmenopausal women consume soy hoping that it might reduce their hot flashes and other symptoms. A new study suggests that adding soy isoflavones to the diet can also produce a healthier distribution of body fat─namely, less fat in the abdomen─which could lead to a number of other health benefits.

The study, published in Fertility and Sterility, included 15 postmenopausal women whose last menstrual period was between one and five years before entering the study. They received either a daily soy shake providing 20 grams of protein and 160 mg of isoflavones or a daily milk-based shake with the same amount of protein and calories. After three months, the abdominal fat in the women taking the soy shake had decreased, but had increased in the women taking the milk-based shake.

For better heart health, say goodbye to the jelly belly

While the total amount of body fat is an important indicator of cardiovascular risk, the way the fat is distributed makes a marked difference. When extra body fat accumulates in the abdomen, a pattern sometimes referred to as the “apple shape,” the implications are much more serious than when it is stored in the hips and thighs, or the “pear-shape.” The apple shape has been linked to increased risk of type 2 diabetes, breast and endometrial cancers, high blood pressure, stroke, and coronary artery disease.

Women producing estrogen have a tendency to develop more of a pear shape, but after menopause, when levels are lower, fat distribution often shifts toward the abdomen. Insulin has the opposite effect: more fat is deposited in the abdomen when insulin levels are high, such as occurs in insulin resistance and type 2 diabetes.

Shake it up with soy

In this study, drinking a daily soy shake with protein and isoflavones reduced abdominal fat, suggesting one possible way that soy might exert health benefits seen in other studies. Dr. Cindy Sites of the University of Alabama at Birmingham, the lead author of the study, said that using the soy shake made it easy for the women to get a high level of soy isoflavones. “Some of the women used the soy shakes mixed with their breakfast cereal, and others tried mixing it with fruit in the blender to make smoothies,” she said.

Getting this daily amount of isoflavones using other soy foods might be more difficult. The equivalents:

• 1 cup of green soybeans, also called edamame

• 1/2 cup of roasted soybeans

• 8 cups soymilk

• 1 pound of tofu, a pound would be needed.

Can eating ordinary amounts of soy foods affect abdominal fat? “Since we only tested the soy shake with a high amount of isoflavones, we don’t know what impact, if any, smaller amounts may have,” Sites answered.

Avoid the apple shape

The best way for postmenopausal women to avoid becoming more apple-shaped is to eat a well-rounded diet that is low in refined carbohydrates (like white flour) and added sugars (including high-fructose corn syrup), and high in:

• whole fruits (not juices) and vegetables

• whole grains

• healthy fats like olive oil, nuts, and seeds

• protein from beans and lentils, fish, and lean poultry and meat

Based on the findings of this study, adding a soy shake might also be a good idea.

(Fertil Steril 2007;88:1609¬–17)