Svatmarama, Hatha Yoga Pradipika ~ When the breath wanders the mind also is unsteady. But when the breath is calmed the mind too will be still, and the yogi achieves long life. Therefore, one should learn to control the breath.
And still lose weight. If you can't go the rest of your life without eating carbs then don't try it to lose weight. The second you put carbs the back into your diet the weight will come right back. It's not what you eat it's how much you eat.