Yes, it's a bit dated - but it's chock full of excellent exercises, nutrition and healthy eating advice, and encouragement. I always go back to it when I fall off track and it helps me get started on the straight and narrow again. It's helped me keep off 50+ pounds these last 20 years.
They don't call him the 'Weight Saint' for nothing!
Combine this book with his exercise DVDs and you can't help but get fit.