Those meters can be wildly inaccurate. The number is likely going up because you are losing lots of water weight since your glycogen stores aren't being chronically topped up with a high carb diet. They work by passing a small electric current from one foot (or hand) to the other. If you have less water in your muscles, the meter will read higher. Measurements (waist, thigh, arm, etc.) and how you look in the mirror are better gauges.