As South Korea airs rising concerns over the North Korean leader’s health, drinking, and weight, Kim Jong-un’s younger sister is pouring out a stream of invective against America for what she calls its “hackneyed gibberish” denouncing the North’s failed attempt at launching a spy satellite.

Armed with the formal title of vice department director of the central committee of the North’s Workers Party, Kim Yo-jong derided America for “its brigandish and abnormal thinking” in a commentary released in English by Pyongyang’s Korea Central News Agency.

One reason Ms. Yo-jong’s big brother, Mr. Kim, may have authorized her tirade is that he may not be in good health. Seoul’s spy agency, in a closed-door briefing for members of South Korea’s National Assembly, reportedly stated that it was “closely watching the possibility” that Mr. Kim, reported to be fond of whiskey and cognac, was “falling into a vicious circle of depending more on alcohol and nicotine and suffering worsening insomnia.”

“N.K. leader estimated to weigh about 308 pounds with significant sleep disorders,” was the headline over a piece put out by South Korea’s Yonhap news agency, which attributed the report to Seoul’s National Intelligence Service. 

Ms. Kim, known for her colorful rhetoric on behalf of her brother, said it was “pitiful that the U.S.-style gangster-like logic” should have accused North Korea of violating sanctions imposed by a resolution of the United Nations Security Council.

The statement did not mention that the satellite had plunged into the Yellow Sea but sought to justify a project that’s widely believed as a chance for North Korea to test the technology needed for long-range ballistic missiles. North Korea distributed images of the launch and has vowed to try again

“The U.S. is a group of gangsters,” Ms. Kim said, for charging that the North’s satellite launch was “illegal and threatening.” It is the “tragedy of the U.S.,” she said, that “it can never give a correct answer with a wrong formula and has not discarded misunderstanding of it.”

Ms. Kim’s tirade comes as Mr. Kim, it appears, has given up on the diet that he seemed to be following two years ago when his weight was estimated to have fallen well below 300 pounds — still too much for a man whose height is about 5 feet, 7 inches, but definitely a sign that he had been seriously dieting.

Los Angeles Times has previously reported that Mr. Kim “has a taste for whisky and cognac,” in particular “Hennessy, which can cost over $6,000 for a high-end bottle.”

The South Korean spy agency’s concerns were “based on the fact that North Korean authorities have been actively collecting the latest medical information, including medications such as zolpidem, for the treatment of insomnia in high-ranking officials abroad,” a member of the assembly, Yoo Sang-bum, was quoted as telling reporters after the closed-door briefing.

The spy agency also provided photographic evidence distributed after Mr. Kim’s last public appearance in May. “Chairman Kim looked very tired with noticeable dark circles under his eyes,” Mr. Yoo, citing “analysis using artificial intelligence of some of his recent photos,” said.

He quoted the spy agency director as saying “scratches and bruises have continuously been observed on Chairman Kim’s hands and arms, which are suspected to be a combination of allergies and stress-induced dermatitis.”

One reason for Mr. Kim’s stress may be the mounting pressure exerted by Washington, Seoul, and Tokyo against the launch of the satellite and the rocket that was supposed to be circling the earth. South Korean vessels and divers are attempting to recover some of the parts from the Yellow Sea 125 miles west of the South Korean coast.

“The U.S. should cool its head heated with confrontation hysteria and clearly look into the UN Charter and the provisions of the space treaty,” Ms. Kim stormed, “before groundlessly denying and pulling up a sovereign state over its satellite launch and its right to space development.”