Going without food

I’M so glad that the four boys who went missing while jungle-trekking in Cameron Highlands have been found, and they are safe and well. In the movie The Ring, it says that one can survive for seven days without food. Is this true? How long can a human body last without food and water? 

Without food, you can last around 60 days if you are a healthy adult with at least 11kg of fat in your body. It all depends on how much body fat you had in the first place. No human being can survive if he loses more than 40% of his body mass.