SAN DIEGO — UC San Diego has begun using its cellphone app to alert needy students when leftover food is available from social events, a service that’s becoming more common as colleges and universities better recognize hunger on campus.

More than 700 students have signed up to receive the notifications, which typically go out 15 minutes before an event ends.

The service offers items including Hawaiian barbecue, pastries, tacos and sandwiches. All students need to do is download the UC San Diego app available for Android and Apple phones.

“We’ve had 50 to 75 students show up within just a few minutes of receiving the notifications,” said John Weng, assistant director of UC San Diego’s Associated Students. “People are very thankful.”

San Diego State has a similar service, notifying students on Twitter about leftovers from the university’s student union, and from some of the social events it holds. The campus also makes it easy for students to track the contents and movements of its food pantry.

To differing degrees, schools nationwide have long helped provide needy students with food — generosity that wasn’t widely known before the age of social media and cellphones.

Educators say the issue has been getting more attention because the rising cost of tuition has affected the ability of many students to cover living expenses, notably food and rent.

In-state tuition has more than tripled over the last 20 years in the University of California and California State University systems, according to the Public Policy Institute of California, a nonpartisan think tank in San Francisco.

There has been special attention paid to “food insecurity,” which the U.S. Department of Agriculture defines as households “having uncertain or limited ability to get adequate food due to lack of financial resources, resulting in reduced quality, variety or desirability of the diet and, over time, reduced food intake and/or disrupted eating patterns.”

Researchers and campuses have produced studies and surveys that have found significant food insecurity in the UC, Cal State and California community college systems.

The problem schools include UC San Diego, which is seen by many people as affluent because it ranks among the 10 richest research campuses in the U.S., and because it is operating a private fundraising campaign that’s expected to raise at least $2 billion.

But roughly one-third of the school’s students come from homes where the total family income is less than $60,000 a year.

The university surveyed more than 7,000 of its undergraduates last year and found that 44% of them had skipped or reduced the size of meals to save money.

“A lot of students who struggle come from low-income families,” said Patricia Mahaffey, assistant vice chancellor of student life at UC San Diego. “But a lot also come from middle-income families who don’t qualify for as much financial aid.

“That leaves a gap, and many end up working. If you work more than 15 hours a week and maintain a full load, well, that’s really rigorous for an institution like this.”

The university has tried to ease the strain by creating a food recovery network that enables it to collect unsold or leftover food from supermarkets, farmers markets and some of the school’s dining facilities. The university has been collecting thousands of pounds of food a week, and will probably face pressure to collect even more. UC San Diego is among the fastest-growing colleges in the country. It added nearly 11,000 students in just the last 10 years.

The campus — like San Diego State — also has been helping students apply for CalFresh, the state’s food stamp program. Last fall, the school helped nearly 600 students apply for the aid, which does not have to be repaid.

“We’d like them to sign up for CalFresh,” Weng said. “It’s dependable.”