Cutting fat when you prepare cakes and other dishes has not been easy as pie. Fat substitutes sold in the past were likely to make food taste like cardboard, or add sugars in place of fat. But our recent tests show that a new fat substitute called Z Trim can replace butter, eggs, and oil in a range of recipes with little or no change in flavor or texture--and slash fat and calories.

Z Trim fat substitute, invented by a chemist at the U.S. Department of Agriculture, is made of bran fiber (from corn, oats, soy, or other grains) and water. We bought the gel form; there's also a powder, which you mix with water. According to the label, a tablespoon has no calories, no fat, and slightly more than half a gram of fiber.

The manufacturer suggests using Z Trim fat substitute to replace some, not all, of the fat in recipes, and that's what we did. To make salad dressing, for example, we used one-quarter cup of Z Trim and one-quarter cup of vegetable oil instead of a half-cup of oil.

Our tasters had a hard time detecting a difference between full-fat and Z Trim fat substitute versions of the dishes we made. Even the Z Trim tuna salad--where we replaced 75 percent of the mayo with Z Trim, shaving off 10 grams of fat per serving--tasted as moist and flavorful as the conventional one.

We could find only one published study of Z Trim in humans, from 2002. It looked at the product's ability to help manage blood-sugar levels and found that it helped, but not as much as other types of fiber. Adverse effects of Z Trim fat substitute were minimal--mainly flatulence, possibly from increased fiber consumption.

Z Trim's main drawbacks are its availability and price. At press time, it was being sold only online at www.ztrim.com. We paid $5 for a 1.18-pound bottle, plus shipping ($8.95 for one bottle; slightly more for extras). Per tablespoon, that totals as much as 40 cents, far more than butter (about 15 cents in our area), mayo (about 6 to 10 cents), and vegetable oil (about 5 cents).

CR's take. If you'd like to reduce your calorie and fat intake, and are willing to pay extra and order online, Z Trim fat substitute is worth a try. It might even curb your appetite somewhat, because fiber helps make you feel full.