BOSTON - At Harvard, they consumed only Gatorade and water for nine days. At the University of Vermont, they subsisted for five days on orange juice, herbal tea, and sea salt. At the University of California, some lived off a potion of lemon juice, maple syrup, and cayenne pepper.

This is not the latest dieting craze, but a controversial trend in student activism: hunger strikes.

Students on at least five campuses went on hunger strikes this year, most of them protesting what they saw as their university’s involvement in unfair treatment of workers. At Purdue University in Indiana, a strike last winter lasted 26 days.

In most of the protests, the hunger strikers claimed to have won concessions. But they have also alarmed university leaders and, on some campuses, triggered a backlash from fellow students.

Hunger strikes demonstrate the depth of passion many students feel about the fight against economic inequality. They also represent a certain desperation, according to some students and labor historians, as universities become less tolerant of public disruptions, such as a high-profile sit-in at Harvard in 2001. While most protests are nonviolent, activists believe that a cultural shift since the Sept. 11, 2001 terrorist attacks has encouraged administrators to crack down on civil disobedience on campus.

Students know they can be arrested or expelled for taking over the president’s office — a time-tested way to get noticed on campus — but they cannot really be punished for forsaking their meal plans.

In society at large, “people are more afraid of dissent than they should be,” said Kelly Lee , who just graduated from Harvard and took part in a hunger strike there last month. “The tactics have to fit the time and the audience.”

Hunger strikes have a long tradition, from Mahatma Gandhi to Bobby Sands , the IRA member who starved himself to death in prison in 1981. But they have not been a dominant form of campus protest in the past.

Some of the recent student hunger strikes have clearly been inspired by those on other campuses. Janitors in a few places have also gone on hunger strikes, but labor leaders say there were no coordinated efforts to enlist students.

Hunger strikes — on campus and off — are a relatively new phenomenon in the labor movement, said Eve Weinbaum , a professor of labor studies at the University of Massachusetts at Amherst. Workers today have less ability to influence their employers, she said, because they are so often part-time employees who are not in unions and, in many cases, are in the country without proper immigration documents.

In the spring of 2001, Harvard students occupied the main administration building for three weeks, demanding the university pay workers a “living wage.” The school eventually agreed; some of the 30 protesters were briefly put on probation, a punishment seen as mild.

This year, activists declared that Harvard security guards, who are employed by an outside contractor, were not being offered a decent contract. Marches and rallies had produced no result, and time was running short before summer vacation.

But another sit-in like in 2001 seemed out of the question. Lee and three other students had been arrested in April for heckling the director of the FBI, which students and officials believe are the first arrests of protesters on campus in decades.

Lee, of Springfield, Ore., said campus police told the detained students that Harvard had a new policy to discourage disruptive protests. So they were worried about taking action that could get them suspended, expelled, or dragged out by police. A hunger strike seemed like the answer.

Before they started fasting, the protesters met with a university health services doctor to learn how to stay as healthy as possible. After five days on their Gatorade diet, they visited the health center for blood tests.

Late that night, Javier Castro received a call from the health center: His sodium levels were dangerously low. Castro learned he had taken in too much water, putting him at risk of seizure or coma even though he felt fine.

He was admitted to Mount Auburn Hospital at 2 a.m. but insisted on fasting for nearly another two days. “It was not the best thing a pre-med like myself could do,” Castro, 19, of Irvine, Calif., said last week. Still, “I definitely think it was worth it.”

However, most of the hunger strike participants have made it clear that they would not be willing to fast to death. At some schools, the protesters weighed themselves daily or had student EMTs take their blood pressure.

“I want to be effective, not dead,” Lee wrote on a blog kept by the Harvard activists.

Fasting was not that uncomfortable, said students who have taken part in hunger strikes. Several described the first few days as most difficult, due to headaches, stomach cramps, and nausea.

But they kept enough energy to go to classes and study for finals. Several described feeling a high or a sense of clarity and well-being on the third or fourth day.

“Basically, your body adjusts,” said Zack Pesavento , who went on a juice-and-salt-only hunger strike at Georgetown two years ago. “On day three or four I felt a sense of peace. I remember on the seventh day thinking, ‘How is it possible that I’m walking around and talking to people?’ ”

Although the hunger strikers managed to avoid punishment, in some cases they also acknowledged that the results were not all they desired.

The Harvard protesters broke their fast when negotiators appeared to be making progress. The guards and the company reached a deal a few weeks later, but only after labor leaders had threatened to disrupt commencement.

Most university officials are loath to comment on the tactics of student protesters. A Harvard spokesman would only refer to official statements expressing concern for the students’ well-being and commitment to the university’s wage guidelines.

Enrique Corredera , a spokesman for the University of Vermont, readily credited the “strong and very passionate” student activism that started long before the hunger strike in April for the university’s decision to reexamine salaries and benefits for its low-wage workers. But he refused to credit the hunger strike , saying it had only added stress and anxiety to students and administrators, without changing the results.

Some students who believe universities should treat workers better see hunger strikes as a distraction. Jessica Coggins , a senior at Harvard, said she agreed with the protesters’ goals but said hunger strikes are “a very alienating tactic” that put lives at risk and discourage more moderate students from attending rallies.

The hunger strikers counter that they needed an extreme form of protest to break though the indifference to their concerns.

Marcella Bombardieri can be reached at bombardieri@globe.com.

© Copyright 2007 The New York Times Company