The shortage of sunny days north of the border could be a contributory factor in the high levels of obesity recorded in Scotland, researchers have found.
Research has found that levels of vitamin D - of which sunlight is the most natural source - tend to be lower in the bodies of overweight people.
Insufficient vitamin D in the blood interferes with the hormone leptin, which signals to the brain when the stomach is full.
Statistics show that more than one in five Scot adults are now obese. The research into vitamin D levels was carried out by Aberdeen University and is published in the scientific journal Bone.
Between 1998 and 2000, data was gathered on 3,100 women living in the north east of Scotland.
Estimates were taken of how long they had been exposed to sunlight the previous year and the amount of vitamin D they obtained from food such as eggs and oily fish.
Researchers found that those with an average body mass index (BMI) of 34 - which is above the BMI measure of clinical obesity - produced 10% less vitamin D than those of average weight.
Dr Helen Macdonald, of Aberdeen University's department of medicine and therapeutics, said: "We think that obese people are not getting enough sunshine, or that what vitamin D they do have is going into fat stores and is not accessible.
"The fact that obese people are prone to low vitamin D levels is a concern in terms of heart disease, the functioning of the immune system and other diseases such as cancer."