The amount of sleep Americans say they get every night has declined from an average of approximately 8.5 hours in the 1960s to slightly less than 7 hours today. There are probably lots of reasons why, but they likely include 24/7 occupations, prolongation of the “day” with artificial lighting, the use of electronic devices at bedtime (blue-wavelength light from these devices delays sleep onset), and the widespread belief that sleep is less of a priority compared to other activities, whether they are work- or pleasure-related.
Not sure I agree with the electronic devices comment at bedtime, mine actually puts me to sleep just as if I was reading a book!
Many studies involving thousands of adults have generally found that those who sleep 5 hours or less per night, but sometimes 6 hours or less, were up to 45% more likely to be obese.
Source: Too little sleep and too much weight: a dangerous duo – Harvard Health Blog – Harvard Health Publications