Demi Moore's former personal trainer is set to reveal how he transformed the actress from a "meaty" middle-aged woman into a svelte stunner in an explosive new book.

In his upcoming exercise manual, fitness expert to the stars, Robb Parr, describes how clients like the formerly "soft"-bodied Madonna and mum-of-three Moore, 45, required intense training to whip their figures into shape.

He writes: "(Demi) lacked a defined waist, carried too much meat on her thighs, and was, by movie-star standards, thick overall.

"To taper her waist, we decided to accentuate her shoulders, creating a V-shape. We trimmed her thighs, shaving off some of the excess fat from above her knees, and accentuated her butt, further emphasizing her waist."

Australian actress Naomi Watts, whom Parr also trained, is said to have started off as "fleshy, and we needed to trim and tighten so that she would fit the mould of a bikini-clad babe".