Which is more important for weight loss: diet or exercise?

Which is more important for weight loss: diet or exercise? When lose weight, is it better to just eat normal and exercise? Or is it better to go on a low calorie diet and exercise?

I%26#039;ve recently heard that diet isn%26#039;t neccessarily guarenteed to give you weight loss, but exercise will. , my aunt got a free trial and paid only $4.95 shipping and handling.