Like a true California girl, Mischa Barton sips a Protein Berry Workout blend for an energy boost. But can a liquid lunch support your diet? "A shake or smoothie can be a great meal replacement, but watch those calories and do your homework," says Fernstrom. "Ask for the ingredients, and know the calories for the size you order." Whether it's called Slim-Fast or Blimey Limey, "you can pack on the pounds treating these shakes as 'snacks' rather than a complete meal," she says.

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