Researchers do not know what, on the average, the amount of sleep is needed for a person to achieve weight loss. In an earlier study, researchers concluded that individuals needed 7 hours of sleep per night, which was about two hours short of the required 8 hours, which is based on the average human body weight. But as the number of studies on sleep and weight gain has increased, so has the range that is estimated, from 7 to 16 hours.
How much sleep is a person need?
There is no official definition, but the National Sleep Foundation has recommended that adults “get at least seven and preferably eight hours of sleep each night, although a person should not require more than 12 hours of sleep each night to function optimally.” 
Does sleep affect weight?
Not everyone needs the same amount of sleep. A recent review of studies of sleep and weight found that individuals with sleep problems tend to gain weight.  In contrast, individuals with healthy sleep habits—such as avoiding alcohol, caffeine, and tobacco, and getting 5.5 to 6 hours of sleep a night—gained less weight as compared to those in the category of those who had sleep problems. 
What is the relationship between sleep and weight gain?
Studies on sleep and weight have found a negative relation. Sleep deprivation was associated with a four-fold increase in body fat and a two-fold increase in metabolic risk factors, including smoking. 
Are there benefits to reducing the amount of sleep? Are there medical benefits for reducing the amount of sleep?
There are several studies that suggest these benefits might be worth the risk. One study was examining the effects of a short-term sleep restriction and showed that participants who received less sleep were less likely to exercise and increase their exercise activity. 
Another study showed that individuals with sleep problems had significantly increased triglyceride levels and decreased HDL levels as opposed to healthy persons. 
A study by Vennemann reported that individuals who experienced sleep deprivation experienced lower levels of immune function, improved glucose tolerance and body temperature, and improved body composition. 
There is no conclusive evidence on medical benefits associated with decreasing the amount of sleep. However, some recent studies suggest increased levels of serotonin during sleep, which increases blood flow and regulates blood pressure. This finding supports the theory that reducing short term sleep can lead to improved health.
Do people need to