Thanks for the advice Mr. President, said his furloughed workforce, but here on planet Earth they make you pay for your groceries.

That was the reaction from a handful of unpaid federal workers to President Trump’s suggestion at a Thursday news conference that grocers are ready to “work along” with customers without money. Trump was trying to explain earlier comments from his Commerce Secretary, Wilbur Ross, who said he didn’t understand why furloughed workers were using food banks.

“When they go for groceries, they will work along,” Trump said. “They know the people. They’ve been dealing with them for years. And they work along.”

No, said a half dozen unpaid workers at the federal building on Golden Gate Avenue in San Francisco, they don’t.

“Sounds like someone who never bought his own groceries,” said Ellen Leonida, a federal public defender. “It’s an offensive thing to say. Groceries aren’t free.”

Leonida was running on a treadmill at the Federal Fitness Center, a gym for federal employees inside the 20-story courthouse and office building. Running on a treadmill is something like working for no money and, to that end, the meter on her treadmill revealed she had covered 2.3 miles without going anywhere.

“I don’t understand how the president could say something like that,” Leonida said.

Nearby, Army Corps of Engineers biologist Beth Campbell was pedaling a stationary bike. She said she had been furloughed before, although at present her paychecks were still coming, so she didn’t need to try out the president’s IOU grocery idea.

“I don’t think it would work,” she said. “There would be so many people doing it. The grocers wouldn’t go along. That’s not how supermarkets work, the ones I know.”

Being forced to work now for a paycheck later, she said, takes its toll.

“It’s so depressing,” she said. “You feel like you’re worthless. It’s not like you’re on vacation. It’s something else.”

A furloughed worker who identified himself only as Hal and who said he worked “someplace upstairs” put down his weights and said the president’s advice was “not realistic and that’s the best thing I can say about it.”

What would happen, Hal was asked, if he tried Trump’s pay-you-later plan at his supermarket?

“I’d be arrested,” Hal said.

Amber Stewart, the fitness center manager, said the effects of the 33-day federal shutdown were trickling down to her, too. Several gym members had cancelled their memberships during the shutdown. Unpaid workers don’t have money for things like gym memberships, especially if they have to pay for groceries while waiting for the “work along” grocery plan to kick in.

Stewart said her gym, like grocery stores, is cash up front.

“It’s $35 a month,” she said. “That’s the reality. You don’t go into a grocery store and get groceries without paying. Not in this world you don’t.”

Steve Rubenstein is a San Francisco Chronicle staff writer. Email: srubenstein@sfchronicle.com