Although the problem of famine has existed for centuries, this year's World Food Day, which will be observed Wednesday, marks several crucial anniversaries, according to the National Committee for World Food Day.

For one, this is the third year Africa has been faced with a food emergency. For another, it is the fifth anniversary of the annual international event, which is held to strengthen the struggle for freedom from hunger and will be marked in nearly 150 countries. Additionally, it is the 40th anniversary of the founding of the Food and Agricultural Organization (FAO) of the United Nations, a group at the forefront of the international effort to build world food security.

It is also the International Youth Year, the International Year of the Forest and the last year of the Decade of Women, each of which links food with other world issues. Plus, 1985 is the 25th anniversary of the Peace Corps and 50th anniversary of the U.S. Soil Conservation Service.

All over the world on Wednesday, people will be joining forces in educational, informational and networking efforts to share in the commitment to solving world hunger. Locally, World Food Day will be observed with the following activities:

On Tuesday:

* Rep. Mickey Leland (D-Tex.), chairman of the House Select Committee on Hunger, and Postmaster General Paul Carlin, along with the Navy Ceremonial Guard and Navy Band, will participate in the issuance of an end-hunger stamp, at 9 a.m. in the Gold Room (room 2168) of the Rayburn House Office Building on Independence Avenue.

* A press conference to announce the winners of the Presidential World Without Hunger Awards, given to the year's greatest contributors to the world hunger cause, at 9:30 a.m. at the Mayflower Hotel. Harvey Korman will act as master of ceremonies for the presentation of the awards, at 11 a.m. at the Terrace Theater in the Kennedy Center. Following the awards ceremony, congressmen Robert Dole (R-Kan.), Richard Lugar (R-Ind.), Thomas P. (Tip) O'Neill Jr. (D-Mass.) and Dante Fascell (D-Fla.) will cohost a luncheon at 12:30 p.m. in the atrium of the Kennedy Center. Cost for the luncheon is $50. A reception will be held from 5 to 7 p.m. at the Department of State, by invitation only. For more information, call Kellan Quinlan. 632-4213.

On Wednesday:

* A ceremony and exhibits kicking off World Food Day in the U.S. Department of Agriculture will be held at 10:30 a.m. in the patio of the USDA Administration Building on 14th Street and Independence Avenue. Secretary of Agriculture John R. Block will be the keynote speaker; M. Peter McPherson, administrator of the Agency for International Development, Loret M. Ruppe, director of the Peace Corps, and Roger Sorenson, North American representative of the Food and Agricultural Organization, will also speak.

* The Second Annual Satellite Teleconference, conducted in a town meeting format, will cover the issues of the relationship between poverty and hunger and the impact of environmental degradation (e.g. soil and water depletion) on global food security. The live broadcast, moderated by WJLA's Rene Pouissant, will include a panel discussion, an on-site discussion and a call-in session. The broadcast, which will originate at George Washington University, will be telecast to 195 sites around the country. Locally, it can be viewed from the chapel of the Abraham Kay Spiritual Life Center at American University and in the main lounge of the University Center at Catholic University. The free program runs from noon until 3 p.m.

* "Approaches to Resolving Hunger and Poverty" is the theme of a lecture program to be held at American University from 2 to 5 p.m. in the School of International Service lounge at American University. Topics for the three-part program are food and agriculture, the crisis in Africa and educational responsibilities. Call 362-4629 or 363-4818 for more information.

* Metropolitan area elementary, high school and international students will sing songs, give speeches and exhibit posters on world hunger. Legacy, a group of international high school students from five Eastern states, will perform a short musical about hunger at 2 p.m. in the patio at the Department of Education plaza at 400 Maryland Ave. SW. The rain location is Health and Human Services auditorium, North Building, 4th Street and Independence Ave. For more information, call Walter Steidle at 245-8412.

* The Washington Cathedral Interfaith Convocation, which will include a procession of children from over 60 embassies and District schools, will be held at 7:30 p.m. at the Cathedral. The Rev. Jesse Jackson, Rep. Benjamin A. Gilman (R-N.Y.), John Denver, Cliff Robertson, Harvey Korman and Dennis Weaver will also take part in the service. Participants are encouraged to bring donations of canned foods, which will be distributed to area soup kitchens and food banks. For more information, call Nancy Montgomery at 537-6247.

On Thursday:

* A "Hunger in the Nation's Capital" conference will be held to discuss networking and explore solutions to problems facing emergency food providers in Washington. Sponsored by the Mayor's Commission on Food, Nutrition and Health, the conference is open to the public for $5 (preregistration), $8 at the door. It will be held from 8:15 a.m. to 4 p.m. at the First Baptist Church at 16th and O streets. Call Janice Morikawa at 332-0440 for more information.

For educational or informational materials for World Food Day (study papers, fact sheets or posters), contact the National Committee for World Food Day at 1001 22nd St. NW., Washington D.C. 20437. Suite 300. 653-2404.