Robert B. Choate Jr., who gave up an engineering career to devote himself to fighting against poverty and malnutrition, seizing national attention in 1970 by telling a Senate subcommittee that most breakfast cereals barely qualify to be called food, died on May 3 in Lemon Grove, Calif. He was 84.

Mr. Choate’s son Valerian said he died as the result of a medical condition that prevented him from swallowing.

Mr. Choate, superficially a tweedy, bow-tied Boston Brahmin, decided in midlife that he wanted to rankle feathers. An early step was publishing a magazine in Phoenix, where he moved in the late 1950s, that deliberately irritated the city’s conservative establishment. Soon he was at the center of a roiling national discussion of how to best use America’s agricultural bounty to nourish its people.

“He was one of a half-dozen people who brought health and malnutrition to the eyes of the public,” Nick Kotz, author of “Let Them Eat Promises: The Politics of Hunger” (1969), said in an interview.