A minimum of 20 million Americans go hungry at least two days a month, and hunger is growing worse because of cuts in federal food programs, a private task force of 22 physicians and public health experts reported yesterday.

The report said that the doctors found family after family whose cupboards were empty or who ran out of food stamps four or five days before month's end.

Doctors or public health agencies in Chicago, Boston, New Mexico and elsewhere found many cases of failure to thrive among low-income children, and a Cook County hospital official said that he sees "15 to 20 cases every year" of kwashiorkor and marasmus, diseases of severe protein and calorie deprivation that usually are seen only in Third World countries.

"We believe that hunger in America is a public health epidemic that afflicts some 20 million Americans," said J. Larry Brown of the Harvard School of Public Health, chairman of the Physician Task Force on Hunger in America. He said $5 billion to $7 billion a year in added outlays for food aid could probably end the problem.

During the past 10 months the privately organized task force, funded by the Field and New World Foundations and other such groups, toured the four regions of the country, visited hundreds of homes of poor people and conducted exhaustive reviews of 15 national studies on hunger and more than two dozen state studies, as well as various public health studies.

The task force's findings differed substantially from those published a year ago by a special presidential task forced headed by J. Clayburn LaForce, dean of the graduate school of management at UCLA, which declined to estimate the number of those hungry, saying that hunger was not "rampant" in the United States although it "did exist."

Brown and four others who outlined Physician Task Force findings yesterday -- Dr. Gordon Harper of Harvard Medical School, Dr. Victor Sidel of Albert Einstein College of Medicine, Dr. Aaron Shirley of the Jackson Hines Medical Center and pastor Kenneth Dean of the First Baptist Church -- said that the hunger found by the task force is not usually characterized by the massive visible physical and mental deterioration found in Ethiopia and other developing countries, but is identifiable and harmful.

Brown said that the study counted a person as hungry if he or she was "suffering some days a month," -- two, three or more -- because of lack of food. Harper and Sidel said that the loss of adequate food for even these short periods can produce a lack of energy, listlessness and dullness that makes it difficult to work or study.

More severe deprivation, Shirley said, makes the body vulnerable to illness.

"It's extremely difficult to actually starve," he said. "You die first from pneumonia, meningitis and other diseases."

In infants, hunger can lead to low birth weight, failure to thrive, death or crippling conditions.

Apart from its surveys and visits, the Physician Task Force reached the 20 million figure by adding the 15 million people who, although below the poverty line and theoretically eligible, do not get food stamps for a variety of reasons (red tape, lack of information, fear of stigma), and the 5 million below the poverty line who do get stamps but who, the Task Force concluded, regularly run out of them before the end of the month.