The profits from levererged loans are shrinking, providing the smallest returns for the start of the year since 2008, Businessweek said.

The article reported that the Federal Reserve and other regulators warn that the $561 billion market may have become too risky. 

"An investor shouldn’t expect to earn what they earned last year because we started with a different set of initial conditions," said Beth MacLean, a money manager at Pacific Investment Management. "This year you don’t have the capital appreciation upside and it’s really more of a coupon clipping year."