The scale is not necessarily your friend. You may want to lose fat – but the scale measures muscles, bone and internal organs as well. Gaining muscle is a good thing. Thus weight or BMI are imperfect ways to measure your progress. This is especially true if you’re just coming off a long period of semi-starvation (calorie counting), as your body may want to restore lost muscles etc. Starting weight training and gaining muscle can also hide your fat loss.
And maybe a new mattress, because it’s not just the amount of time you spend sleeping that keeps you lean, it’s also the quality of your sleep. Fat cells in your body produce a hormone called leptin that helps the body keep track of how much potential energy (i.e. fat) it has stored. But leptin is only produced during certain stages of sleep. Miss out on those stages because you’re not resting soundly enough, and you’ll disturb levels of the hormone, leaving your body with no real idea of its energy reserves. Consequently, you’ll end up storing calories rather than burning them.