Give up the goods on Nxivm? Fat chance.

The alleged sex-cult’s bookkeeper refused to give prosecutors the skinny on the upstate group, invoking her right to remain silent more than 80 times during grand-jury questioning — even when asked something as mundane as her weight.

Kathy Russell, 61, invoked her Fifth Amendment privilege against self-incrimination 50 times during her first one and a half hours of testimony and another 32 times after returning from a break, according to newly unsealed court papers.

The slender numbers-cruncher appeared before the grand jury last summer as it investigated the group and its leader Keith Raniere, who was accused of sexually abusing young girls.

“The Government … engaged Russell in an extended conversation about whether she had ever asked Raniere about allegations that he had sexually abused minors or raped a particular woman,” the papers say. “The Government noted that it had evidence that Keith Raniere had had sex with underage girls.”

Russell declined to answer any related questions.

But she also “invoked on a wide variety of topics, some of them seemingly mundane, including her level of education” and her weight, the court document said.

Russell was indicted on two counts of racketeering conspiracy a month later, in July 2018, for her role in the group, which prosecutors say operated a secret section called DOS in which women were starved, branded and groomed to have sex with Raniere.

Russell is in continuing plea negotiations with prosecutors.

Other high-level Nxivm members, including “Smallville” TV actress Allison Mack and front-line DOS master Lauren Salzman have since pleaded guilty. Nxivm co-founder Nancy Salzman has also entered a guilty plea.

Raniere and his benefactor, Seagram’s heiress Clare Bronfman, are expected to take their cases to trial.

Opening statements are scheduled for May 7.