How much is too much?

I have been training the past 10 weeks, 5 times a week (cardio + weight training). I have decided to increase my training to 8 times a week, to increase my results of losing weight and toning up. I have so many critics around me saying that too much training is not good for one? Obviously they do not have much to back it up, but has played on my mind a bit and is de-motivating me. So I am asking is there such thing as too much training, if so what is too much?

It becomes too much when you start feeling strain on your body and you know it's definitely too much when you injure yourself and you don't want to do that.
It is best to be gradual and maybe start with 6 times a week, see what happens after a few weeks or a month of training 6 times a week. But don't go straight from one thing to another without knowing how much it is really affecting you. If you feel strain with 6 you can always go back down to 5 but if you go directly to 8 you are taking a bigger risk and you don't want to damage or sprain anything or overwork yourself.