Thirteen-year-old Christian Schulze loves the new Burger King near his German home, but limits his cheeseburger binges to once a week. James Ojiambo, 14, of Kenya has started exercising to develop "mighty muscles," and Gry Engebakken, 12, of Norway stopped eating "fat foods" to lose weight.

These youngsters are among 20,000 children from 14 countries who learned healthful diet and exercise habits as part of a health evaluation and education program called "Know Your Body."

Fifty of the children visited the United States last week to celebrate Know Your Body Week, an international Children's health pageant. The "good health ambassadors" won the trip as a prize in a poster contest.

Sponsored by the American Health Foundation in New York, the Know Your Body project was begun in 1975 in school systems around the world, including Japan, Germany, Italy, France, Nigeria, Yugoslavia and Kuwait.

The children, who ranged in age from 10 to 14, were screened to measure height and weight, blood pressure, skin fold thickness, blood serum cholesterol and general physical fitness.

A comparison of these measurements, released last week, shows that "many countries are dooming their children at an early age to a lifetime of chronic disease," says foundation president Dr. Ernst Wynder, New York. "Each society is responsible for the obesity, smoking, drug abuse and alcoholism of its children.

"Diet and behaviors are established early in life. As a member of a particular society, a child learns to eat what we eat, smoke what we smoke, drink what we drink and underexercise like we underexercise."

Health problems already present in the children, he says, mirror the incidence of the related disease affecting the adult population of that country.

The children from Finland, for example, had very elevated cholesterol levels due to their high consumption of dairy products. "This diet establishes an early pattern for the significantly higher rate of heart attacks among the Finnish adults," says Wynder.

"The fact that risk factors reflect cultural attitudes indicates that these risks are largely related to life style. Children can be trained to live an appropriate life style, just as they can be trained to read and write."

Prevention-oriented health education "should be as integral a part of a child's education as math and English," asserts Wynder, who says his school-supported Know Your Body Program costs $25 per child.

Students in the program are bringing fruit to school in their lunch bags instead of candy, and early indications show they eat better exercise more and smoke less, he says.