If you are not eating much at all then you'll have put your body into economy mode.
I eat according to Atkins, and so don't think about calories, use cream and oily salad dressings, I only restrict carbs, so nothing over 10 percent carbs, lots of green salads, low carb vegetable mixes, small portions of peas and green beans, but no other legumes. On this level before diagnosis I would have been losing more weight each week, but I spent too long on the so called cholesterol lowering diet and getting into ketosis is far harder now.
The amount of carbs you eat, and where it is sourced is important, and it isn't a fixed diet sheet way of eating. You need to establish your carb count for losing weight, and which foods you can and can't eat - as it varies person to person. That is the great thing about doing Atkins, you eliminate all but the lightest carb foods, then see what happens as you go through the process - some people find they can eat quite a lot of some foods and still lose weight, others discover which foods stop their weightloss. You do need to weigh and measure, and ensure that you are not doing low calorie as well as low carb.