JACKSONVILLE, N.C. — When Billy Sewell began offering health insurance this year to 600 service workers at the Golden Corral restaurants that he owns, he wondered nervously how many would buy it. Adding hundreds of employees to his plan would cost him more than $1 million — a hit he wasn’t sure his low-margin business could afford.

His actual costs, though, turned out to be far smaller than he had feared. So far, only two people have signed up.

“We offered, and they didn’t take it,” he said.

Evidence is growing that his experience is not unusual. The Affordable Care Act’s employer mandate, which requires employers with more than 50 full-time workers to offer most of their employees insurance or face financial penalties, was one of the law’s most controversial provisions. Business owners and industry groups fiercely protested the change, and some companies cut workers’ hours to reduce the number of employees who would be eligible.

But 10 months after the first phase of the mandate took effect, covering companies with 100 or more workers, many business owners say they are finding very few employees willing to buy the health insurance that they are now compelled to offer. The trend is especially pronounced among smaller and midsize businesses in fields filled with low-wage hourly workers, like restaurants, retailing and hospitality. (Companies with 50 to 99 workers are not required to comply with the mandate until next year.)