If i'm on a low carb diet for a week then i go back to carbs can i lose weight ?

Not for long!: You might lose a couple pounds the week you are on the diet but will almost certainly gain it back as soon as you go back. Research proves short-term diets don't work! the best way to permanently lose weight is to make permanent dietary changes you can follow for years. My favorite diet for both weight loss & optimal health: http://www.Drfuhrman.Com/library/what-is-a-nutritarian-diet.Aspx.