Scientific studies linking dietary fat with cancer and heart disease should prompt the U.S. Department of Agriculture to require fat labeling of hot dogs and luncheon meats, says Public Voice for Food & Health Policy, a Washington consumer organization.

In a petition submitted to the agency on Monday, the consumer group asked that all processed meat products be labeled with the percentage of calories that come from fat and the total amount of fat in grams.

A slice of beef/pork bologna contains six grams of fat, with 77 percent of its 70 calories coming from fat. (The rest come from protein and carbohydrates). In comparison, a three-ounce serving of tuna fish contains seven grams of fat. Yet only 38 percent of its 167 calories come from fat.

The fat/calorie approach, said Ellen Haas, director of Public Voice, gives consumers "a signpost" of whether a product is high, medium or low in fat. Although other food products should have fat/calorie labeling as well, Haas said, processed meats -- a major source of dietary fat -- are "a good place to start."

Currently, no government regulations require any processed meat products to carry information about fat content, unless the product makes a nutrition claim, such as "light." Then the amount of fat must be listed in grams.

Supported by nearly 20 consumer and health organizations, the petition also requests that the USDA conduct a study to determine if processed meats contribute an undesirable amount of fat to the American diet.