Demi's in The Zone

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Demi Moore may have three daughters and be the wrong side of 45, but she has a body that's as youthful as her toyboy husband Ashton Kutcher and always looks gorgeous.

Demi's diet: The Zone diet is the brainchild of American nutitionist Barry Sears. It advocates a 40:30:30 approach (40% of calories from carbs, 30% from protein and 30% from fat); regular meals (at least 5 small meals a day); fixed meal times; 'good' fat (from plant oils, oily fish and nuts); and lean protein (from lean meat and fish). The Zone diet stabilises insulin levels, stops the body from storing fat, and helps you lose weight without getting hungry or run down.

Our expert says: "This diet is less severe than a protein diet that involves eating lean animal protein or protein powder. It contribues to weight loss and helps develop muscle mass. That said, it shouldn't be permanent, because your body doesn't need that much protein: 15% of your daily calorie intake is the RDA, and that's enough."

Check out our diet guides for more on The Zone and high-protein diets.