Katie Holmes appears to be on a detox mission after the festive period.

The actress – who is already incredibly slim - was spotted with a bottle of calorie-burning drink Celsius last night.

The actress’ bodyguard clutched a bottle of the diet-aid, along with Katie's lunch box, as she made her way to another performance of Arthur Miller play All My Sons at the Gerald Schoenfeld Theatre in Manhattan.

According to the manufacturers, Celsius is a ‘thermogenic blend’ which increases metabolism and is one of a range of calorie-busting drinks on the mark that are popular with body-conscious stars.

It's reported that Katie will head to a US Gold Base centre when her Broadway run finishes at the end of this week, to take part in a Scientology-approved herbal detox plan.

"The Clear Body, Clear Mind plan utilises a regime of exercise, sauna sweat-out, vitamins and minerals to cleanse bodies of toxins," a source told the Mail on Sunday.

"Katie is tired from balancing motherhood with her six-nights-a-week show and wants to get back into shape.

"The plan involves doses of the vitamin niacin to purify the body."

Judging by her drawn appearance, we think Katie is more in need of a good night's sleep...