Sure it can be done, although according to your profile you are 5'9-1/2" tall and 140 sounds a little low to me. However, you have to decide to do it. If you keep going back and forth between eating lowcarb and high carb you will not lose the weight. If the scale is bothering you, try staying away from it for a few weeks.

I find that I only lose if I stay away from all lowcarb fankenfoods -- shakes, bars, artificial sugars, lowcarb breads and cereals, etc. I eat meat, fish, chicken, eggs, tons of vegetables, some cheese, some berries, occasional melon, and some nuts. I make my own salad dressings with olive oil and red wine vinegar. I've lost consistently for 1-1/2 years now, although it has slowed down.