Why is sleep so important for weight loss?

 # Poor Sleep Is a Major Risk Factor for Weight Gain and Obesity
A Huge review found that short sleep duration increased the chances of obesity by 89% in children and 55% in adults. That’s just in people averaging around 5h of sleep per night and its scaleable, the further you get from optimum levels of sleep the more likely you are to gain weight.  
(https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2398753/)

# Poor Sleep Can Increase Your Appetite
Many studies have found that people who are sleep-deprived report having an increased appetite
(https://www.ncbi.nlm.nih.gov/pmc/articles/PMC535701/)

When you do not get adequate sleep, the body makes more ghrelin (hunger causing) and less leptin (tells your body you are full), leaving you hungry and increasing your appetite.

A study of over 1,000 people found that those who slept for short durations had 14.9% higher ghrelin levels and 15.5% lower leptin levels than those who got at least 7h sleep. The short sleepers also had higher BMIs 
(https://www.ncbi.nlm.nih.gov/pmc/articles/PMC535701/)

# Sleep Helps You Fight Cravings and Make Healthy Choices
Reduced sleep actually alters the way your brain works. This may make it harder to make healthy choices and resist tempting foods. The reward centres of the brain are more stimulated by food when you are sleep deprived.

A study of 12 men observed the effects of sleep deprivation on food intake.
When participants were only allowed four hours of sleep, their calorie intake increased by almost a quarter, and their fat intake almost doubled, compared to when they were allowed eight hours of sleep.
(https://pubmed.ncbi.nlm.nih.gov/20357041/)

# Lack Of Sleep Can Reduce Physical Activity
A lack of sleep can cause daytime fatigue, making you less likely and less motivated to participate in exercise or sport.
In addition, you’re more likely to get tired earlier during physical activity.

Getting more sleep may even help improve performance. No studies for this one. You will have felt it yourself. I know I have