1) Poor sleep is heavily linked to a higher BMI and weight gain. Everyone has differing sleep requirements but research has seen changes in weight when people get less than 7 hours sleep a night. In fact, the shorter your sleep, the more likely you are to see a gain in weight leading to obesity by 89% in children & 55% in adults.
A study showed 16 adults, who were given just 5 hours sleep for 5 nights, gained an average of 1.8lb (0.82kg) over the course of the study. Lack of sleep caused by weight gain has also been linked to the exasperation of sleep apnea.
2) Poor sleep can increase your appetite. The reason for this is likely to be the impact on 2 hormones - ghrelin and leptin.
Ghrelin is released in the stomach and signals hunger to the brain. Leptin is released from fat cells and it suppresses hunger and signal fullness to the brain.
When you are sleep deprived the body makes more ghrelin and less leptin leaving you feeling hungry and increasing your appetite. A study of 1,000 people found those who slept for short periods had 15% higher ghrelin and 15.5% lower leptin, than those who had adequate sleep.
3) Sleep helps you fight cravings and make healthy choices as sleep deprivation will dull the decision making frontal lobe and this leads to a lack of self control. A study of 12 men who were allowed only 4 hours sleep, increased their calorie intake by 22% and their fat intake almost doubled, compared to those who had 8 hours sleep.
4) Poor sleep may decrease your resting metabolism (the number of calories your body burns when at complete rest). Another study of 15 men, who were kept awake for24 hours had a 5% decrease in the resting metabolism than after a normal nights sleep and their metabolism was 20% lower after eating.
5) A study of 10 overweight adults on a 14 day diet of moderate calorie restriction, were allowed either 8.5 or 5.5 hours sleep. Both groups lost weight from both fat and muscle, but the ones who were given only 5.5 hours to sleep lost less weight from fat and more from muscle.
The evidence is stacked in favour of getting yourself a good nights rest in order to kick start losing those pounds.