Will I lose my Whatsapp chat history if I updated my iPhone OS version?

I'm using an iPhone 3GS with iOS 4+ and I've been wanting to update to iOS 5+ for a long time, but I'm afraid of losing all my Whatsapp conversations once I update. Will I really lose all my chat history? And if so, is there anyway I can easily backup the chats?

Yes, you will lose your app data. I'm afraid syncing it won't help. Maybe SSH into the iPhone's core files and save the data there.