Daily Exercise Recommendations?

[K to the J]

I recently researched the Dr. Oz diet and the diet basically consisted of limiting your calorie intake of what's recommended, eat when you're hungry, eat about six meals a day, and the only exercise requirement was 30 minutes a day of WALKING.

I'm not sure whether or not this diet actually works, but it seems like an easy-to-follow and possibly-effective diet plan.

What is a daily exercise recommendation? 30 minutes a day of simply walking, I wouldn't think, should/would cut it.