You need to weigh yourself everyday, or often, and you'll notice a downward trend on the lowest number, if you are losing weight. A few weeks ago, my range was 11 stone 12lb to 12 stone 5lb. my lowest number now is 11 stone 10lb with a high up to 11 stone 13lb. You typically carry 48 hours worth of food and plus there''s the hydration aspect at 1kg per litre of water which will cause significant daily fluctuations. You need to look at the trend and not the number on a particular day. Try graphing your progress and you'll see it better.