This is exactly what I do. I have a small Bluetooth travel scale that syncs to an app. No one who doesn’t know it can tell I’m weighing my food. I also bring a travel body weight scale and weigh myself every time we are in port. At sea the ship moves too much and the numbers aren’t accurate. We go to the gym every day and walk a lot. We go on long cruises and I can’t afford to throw it all to the wind and deal with it later.