severe protein- and calorie-deficiency diseases usually seen only in Third World countries -- have been reported in Chicago, Texas and New Mexico, doctors told a House Select Committee on Hunger yesterday.

Dr. Jean Mayer, president of Tufts University and a well-known nutritionist, said serious hunger was all but eliminated in the United States in the 1970s, but "now that situation is altered. The cutbacks in funding since 1980, coupled with inflation and recession, have wiped out as much as a third of the gains."

The House hearing was called to explore the extent of hunger in America and its effect on public health.

A presidential task force reported in January 1984 that hunger existed but was not "rampant" and that severe malnutrition was rare. A physicians' task force headed by Dr. Larry Brown of the Harvard School of Public Health said recently, however, that while severe malnutrition was not widespread in the United States, at least 20 million people involuntarily go without food at least two days a month.

Mayer said food stamps and the women-infants-children (WIC) program are extremely cost-effective in saving children from serious health problems. Studies suggest that "every $1 spent on WIC saves $3 in the first year" on the health care of children who might otherwise be born prematurely or with low birth weight, a primary cause of infant mortality.

This calculation "does not even count" later costs for children born retarded or otherwise disabled because of nutritional deficiencies.

"Of all the stupid ways of saving money, not feeding pregnant women is the most stupid, the second most stupid being not feeding hungry children," said Mayer, who was a World War II French resistance hero and organized the first White House conference on Hunger in 1969.

Dr. Katherine K. Christoffel, a Chicago pediatrician, said she had documented 16 cases of kwashiorkor and marasmus at Children's Memorial Hospital there during four years plus many other cases of somewhat less extreme nutritional deprivation among poor children.

A child with marasmus achieves only 60 percent of expected weight for his age because of inadequate nourishment. Kwashiorkor, characterized by stunted growth and a protuberant belly, is caused by chronic deficiency of protein and calories.

Colleagues in some of Chicago's 79 other hospitals also said they were seeing these diseases, according to Christoffel, and "they say they are seeing a lot more of it now."

Dr. Aaron Shirley of Jackson, Miss., said doctors in New Mexico and Texas also had reported cases, while others had reported rising rates of infant mortality and failure to thrive because of deficient nutrition.

Ernesto Pollit, of the University of Texas School of Public Health, said that studies here and abroad suggested that iron deficiency was rising in the United States and "interferes with cognitive thinking," leading to lower scores on mental development tests and "deficits in attention and in learning new concepts."