Secretary of Agriculture John R. Block and his family wrapped up a week on the department's maximum food stamp allotment of $58 yesterday. Block called the diet "quite adequate" at a news conference on the Mall, and then joined in a mile-long celebrity run kicking off a "Food and Fitness" fair.

"I report that it is enough food," Block told reporters, but "it's impossible to really appreciate the plight of the poor, and we don't pretend to."

Block, a millionaire who owns a 3,000-acre farm in Illinois, appeared at the news conference with his wife, Sue. They reported that the family spent $56.62 for food during their week on food stamps, which began with breakfast last Friday and concluded with yesterday's dinner.

Block, his wife, their daughter, Christy, 19, and Joyce Hamilton, 19, a friend of Christy's, adhered to the department's "thrifty meal plan," designed for low-income families. No one lost or gained weight, Block said.

Block allowed his family the maximum food-stamp allowance of $58 for a family of four, which goes only to food-stamp families with no income, because he wanted to see how the poorest families live.

Block said he "missed most" his weekly ice cream sundae, and would have liked to have had a beer or a soft drink on the sticky Washington evenings during the last week. Last Saturday night's dinner, selected from sample menus in the USDA publication "Making Food Dollars Count," consisted of chicken-apple salad, green beans, boiled potatoes, muffins and rice pudding.

Sue Block said she was sobered by the amount of time and restraint required to adhere to the stringent budget.

The Blocks' final meal last night was chicken and dumplings, according to an Agriculture spokesman. The secretary's first meal off the food-stamp budget, breakfast this morning, "will be whatever the airline serves," according to the spokesman. Block was to leave this morning for a tour of Latin American nations.

When he began the experiment, Block vowed not to munch at embassy or administration functions which he attends regularly, and he stuck to that vow yesterday under what some might have considered extreme conditions.

After running a 7-minute mile in a celebrity race under the pre-noon heat of the Mall, Block toured a number of tents with exhibits extolling the virtues of fruit, vegetables and milk.

In blue nylon running shorts, his T-shirt soaked with sweat and sticking to his chest, Block was photographed twice in front of the milk displays tipping a glass of milk to his lips, but each time he refused to drink.

"No, I'm not supposed to drink it," he told milk officials who encouraged him to drink up. "I'm still on the food-stamp program." He did not even get any water after running the race with about 200 others, including Sens. Max Baucus (D-Mont.), Richard G. Lugar (R-Ind.) and Larry Pressler (R-S.D.), former Redskins coach George Allen and 28 crewcut members of the Army's 3rd Infantry Regiment.

The race kicked off a three-day "Food and Fitness" fair hosted by the Agriculture Department under tents on the Mall opposite the department's headquarters. The fair featured actors dressed as fruit, the reigning National Watermelon Queen and a cornucopia of fresh produce, from mushrooms and green apples to milk and grilled steak.

With two meals on the food-stamp regimen to go, Block took the podium to tell an audience of tourists and Agriculture personnel that "the abundance and variety of food in America means that there is every reason for people to take advantage of the opportunity to be healthier and more physically fit."