When it comes to saving, although millennials are really pretty savvy about the need to start early in putting money away for retirement, they face some stiff challenges in doing so—such as whether to keep a roof over their heads or put food on the table.

New research from Cerulli finds that low-salary jobs force millennials to choose between immediate needs—buying food or paying their rent—and a goal that's actually decades away, and that distant goal often loses.

While its 2017 survey of 1,000 active 401(k) plan participants show that a majority (85 percent) of participants think people should start saving for retirement before age 28, Cerulli says that only slightly more than half (55 percent) actually did so.