The study reviewed investigated the effect of moderate calorie restriction for 14 days with 8.5 or 5.5 hours of night time sleep (Nedeltcheva AV, et al. 2010). The objective was to see if sleep restriction had an effect on fat loss. Fat loss and fat free mass were two of the things measured. The results were very interesting showing that when the participants slept 5.5 hours they lost 55% less fat compared to when they slept 8.5 hours. What was also surprising was that when they slept less they lost 60% more fat free mass than when they slept more. Losing fat free mass like muscle tissue is neither healthy or productive in the long run if you want to lose weight and stay lean, since muscles are metabolic active tissue which help you burn calories. If you want to get healthier and stay lean you need to lose fat, not muscles. This research reminds us of how important it is to get enough sleep, it is even affecting the way we lose weight. Sleep enough, exercise regularly and eat meals that promote a lean body composition.