If you are on a low carb diet the way to stop losing weight is to focus on the protein and fat. Get some good quality whey powder for protein and add to anything you can, soups, casseroles, kumera, non sweetened soy milk. Get lots of good fat by cooking with olive, macadamia, sesame oils, eat the nuts not prone to mould (eg macadamias and brazil are high in energy). Avocado is a good source of energy and good fat.
As for carbs I think thin ppl need to eat some but stick to low GI (glycemic index) carbs. Find out more about GI here. http://www.glycemicindex.com
I think the diet is important but is not the complete answer.