Post-Christmas weight gain is nothing new, but for champion mare Black Caviar it is proving a major setback to her much-anticipated return to the track in 37 days, reports the Herald Sun.

After a six-month sabbatical, at Peter Moody's Caulfield stables last week trainers were unable to fit the stunning horse into her compression suit.

Tipping the scales at 610kg, it's little wonder why.

At the Diamond Jubilee Stakes in mid 2012 her race weight was a massive 70kg lighter (540kg) as she strode ahead of racing's best sprinters and claimed an infamous victory at Royal Ascot.

In racing terms, even her 540kg race weight is heavier than most horses she lines up against, which are normally another 70kg lighter.

Moody is preparing the mare for a race just one month away on February 16. Named in her honour, the 1000m Black Caviar Lightning Stakes at Flemington could be the race to end her 22-race undefeated streak.

However if she does not get race-fit in time, it is likely Moody will push back her return an extra five weeks.

"She's a big, strong girl now, probably bigger and stronger than she's ever been," said trainer Peter Clarke.

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