What is hidden in 3D image?

A blonde is overweight so her doctor puts her on a diet. "I want you to eat regularly for two days, then skip a day and repeat for two weeks and you'll lose at least five pounds." When the blonde returns, she's lost nearly 20 pounds. The doctor exclaims, "That's amazing! Did you follow my diet?" The blonde nods. "I thought I was going to drop dead every third day from all the skipping!"