In Pyongyang, some families make fewer trips to restaurants and choose cheaper domestic goods over more expensive imports. Outside the capital, rural families now sometimes make do with only two meals a day.

“My worry is that the gains and progress made in recent years in terms of food security and marketization could fade as a result of the sanctions,” said Katharina Zellweger, who has visited North Korea 70 times since 1995, living there from 2006 to 2011 to run a Swiss aid program. “That would mean we are moving backward.”

One Chinese trader who does business with middle-class North Koreans said that he had noticed a growing discontent with the government because of the shortages.

“I can feel they are not satisfied with the government, and if the authorities cannot resolve the sanctions problem, such dissatisfaction will go on and on,” said the trader, who asked to be identified only by his English name, Terry, for fear of repercussions in North Korea. “They have lost the loyalty toward the regime.”

But the Kim government still has enormous power to suppress or deflect discontent. No organized antigovernment resistance exists in North Korea, where the government maintains a tight grip on society and relies on the police, backed by a system of informers, to imprison critics.

Complete control over the news media, and the North’s almost total isolation from the internet, allows the government to shape how many people perceive reality. Bombarded by daily propaganda appeals, North Koreans are more likely to see themselves as citizens of a small nation persecuted by hostile Americans than they are to blame Mr. Kim’s government for their economic hardship, recent visitors and defectors say.

“These ineffective sanctions are being used as propaganda tools to further flame anti-American sentiments,” said Kim Tae-hoon, co-founder of DoDaum, a humanitarian group that has organized an H.I.V. diagnosis and treatment program in the North.

“We do ask people about sanctions,” said Linda Lewis, the North Korea country representative for the American Friends Service Committee, a humanitarian aid group, who last visited in November. “We ask about the impact of them. The answer that we usually get from people is: ‘We’ve never experienced a life without sanctions, so how would we know?’”