This trace mineral may aid obese people, who can be glucose-intolerant or insulin-resistant, says Shilstone. When this triggers insulin production, blood sugar levels peak, increasing multivitamins diabetes risk and making weight loss more difficult. Chromium mitigates these effects by keeping blood sugar levels steady.
Cautions: People who are taking insulin and those diagnosed with hypoglycemia or metabolic syndrome should not take chromium without their physician's approval.
Dosage: Since chromium can be hard to get consistently from the typical diet, a supplement is often the best way to go. Shilstone advises taking 200 to 400 micrograms daily. (Many contain 120 mcg.)
Aka bitter orange or zhi shi, this fruit derivative is used for a variety of purposes in Traditional Chinese Medicine. One of its metabolism-boosting and appetite-curbing ingredients, synephrine, is chemically similar to ephedrine, says Blumenthal, which has caused it to be condemned by association. Research showing bitter orange raises blood pressure and heart rate was done using IV administration, he notes, while "studies on oral dosing fail to show either side effect."
Cautions: The FDA has recorded "adverse events" from taking bitter orange; in most cases, the supplements also had caffeine or ephedra." Only one stand-alone bitter orange supplement was tied to an adverse event," Blumenthal says. Still, he advises those with heart disease or hypertension to always consult their health-care provider.
Dosage: "Stay in the 200- to 400-milligram range," suggests Evan Fleischmann, N.D., a naturopath in New Jersey and New York.
Conjugated linoleic acid inhibits lipoprotein lipase—"an enzyme made by the fat cell that's responsible for the uptake of fat by the cell," explains Mark E. Cook, Ph.D., a professor of animal sciences at the University of Wisconsin, Madison. Extensive research shows CLA prevents the accumulation of fat as animals age, but short-term human studies are less conclusive. "The fat reduction was slow or modest, but fairly consistent," says Cook; so while CLA has been shown to reduce body fat, it may be better at preventing fat accumulation.
Cautions: One 12-week study of people taking CLA found side effects of mild to moderate gastro-intestinal symptoms. The supplement may also increase markers of inflammation, such as isoprostanes, a confusing result as animal studies have clearly shown CLA to be anti-inflammatory.
Dosage: Cook recommends a range of 2 to 6 grams per day. "An average of 3 grams daily is a typical dose," he says. Taking CLA capsules with meals improves absorption.