NBC hasn’t had much working for it in primetime in recent seasons, but it could always count on “The Biggest Loser” — at least until now.

The weight-loss competition series has been shedding viewers of late, and NBC’s scheduling is partly to blame. No weekly Big Four entertainment series airs more frequently, with “Loser” typically playing originals in 33 of the season’s 36 weeks.

Asking audiences to commit to two-hour blocks of time for 13 weeks in the fall and then again for the first 20 weeks at the start of the new year is simply too much. Other reality vets that air two editions each season, like “Dancing With the Stars,” “The Amazing Race” and “Survivor,” take a couple of months or more off, and they have held up better later in their lifespans.

“Loser,” which bowed in October 2004 and has aired mostly on Tuesdays, peaked in 2009 — when its fall edition wrapped in December with a 5.0 rating in adults 18-49 and 13.5 million viewers overall. It has since closed fall with a 4.0 rating in 2010 and then a 2.7 last month, when it drew just 7.8 million total viewers, according to Nielsen.

Continuing the trend, more viewers fled when “Loser” kicked off its latest edition Jan. 3 with a 2.4 demo rating — off 27% from last year (3.3) and 48% from 2010 (4.6).

But the decline of “Loser” isn’t necessarily a bad thing for NBC long-term. The net is in dire need of scripted hits, and won’t find any on Sundays in the fourth quarter, when it devoted its entire sked to football; and with “Loser” gobbling up most of Tuesday all season long, sked space has become limited.

One option for NBC would be to pare the show down to an hour on Tuesdays or perhaps limit “Loser” to one edition each season.

The Tuesday 9 o’clock hour, for example, is prime real estate for a young-skewing drama, and perhaps the Peacock can take advantage of that opening next fall.