Putting on some pounds in the cold season may be inevitable, but some sunlight might help you slim down, a new study reveals.
Scientists at the University of Alberta in Canada discovered that fat cells that lie just beneath the skin are sensitive to the blue light emitted by the sun.
During the winter, these fat cells are largely shielded from the sun's rays, giving them a chance to grow and build up, but they shrink when they are exposed to more light in warmer months.
The cells' responses to sunlight also suggested to the researchers that the skin and fat may play a role in maintaining our internal clocks.
Sunlight may help to shrink fat cells that build up during shorter winter days, a study suggests
Sunbathing does not immediately spring to mind when thinking about getting in shape.
But the research provides another reason to bask in the sunshine - a modest amount, with sunblock to protect you from skin cancer - in the summer, beyond boosting levels of vitamin D.
Study co-author and director of the university's Alberta Diabetes Institute, Dr Peter Light, explained: 'When the sun's blue light wavelengths - the light we can see with our eye - penetrate our skin and reach the fat cells just beneath, lipid droplets reduce in size and are released out of the cell.
'In other words, our cells don't store as much fat.'
Lipids are fats found in the blood, including cholesterol and triglycerides, levels of which rise when we put on weight.
Dr Light added: 'If you flip our findings around, the insufficient sunlight exposure we get eight months of the year living in a northern climate may be promoting fat storage and contribute to the typical weight gain some of us have over winter.'
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ShareFor the US and Canada - where 70 and 25 percent of the populations, respectively, are overweight - in the northern hemisphere, this may be particularly true.
Research has shown people tend to gain five to seven pounds on average during the winter months.
It has been blamed on a range of factors from eating more comfort foods to combat the 'winter blues' to doing less exercise and there being fewer fresh fruit and vegetables from which to choose.
But the breakthrough study published in Scientific Reports is the first ever observation of the 'sunlight' phenomenon.
Dr Light hopes it could lead to the development of new drugs, or even light therapy, to combat obesity, diabetes and other related health issues.
He warned the finding is only an initial observation and sunbathing is not yet a safe or recommended way to lose weight. But he says getting the right amount may play a role.
CAN YOU EAT YOUR SPF? WHAT TO EAT TO PROTECT YOUR SKIN
Eating certain pigment-rich foods daily can contribute to building up the skin's natural barrier to the sun's harmful rays.
Particular fruits and vegetables such as dark purple berries and dark green veggies contain special protective compounds, and it's all down to their concentrated pigmentation.
Dermatologists and skin scientists at the forefront of photo-dermatology (the scientific study of ultraviolet light and its effects on skin) have made the pioneering discovery.
The body utilities the food's compounds near the skin's surface to give a base level of protection against damaging UV rays.
Known as a Continual Dietary-Sun Protection Factor (CD-SPF), this is the first time scientists have ascribed an SPF value to diets based on the nature and quantity of natural plant pigments.
Foods that have natural SPF qualities
- Blackcurrants
- Blueberries
- Blackberries
- Black grapes
- Figs
- Oranges
- Butternut squash
- Dark green peppers
- Kale
- Spinach
Dr Light said: 'For example, we don't yet know the intensity and duration of light necessary for this pathway to be activated.'
He speculated: 'Maybe this mechanism contributes to setting the number of fat cells we produce in childhood - thought to stay with us into adulthood.
'Obviously, there is a lot of literature out there suggesting our current generation will be more overweight than their parents and maybe this feeds into the debate about what is healthy sunshine exposure.'
His team made the discovery while investigating how to bioengineer fat cells to produce the glucose regulating hormone insulin in response to light, to help patients with type 1 diabetes.
'It was serendipitous,' said Dr Light, adding his name is an ironic coincidence since light was not his primary field of research.
'We noticed the reaction in human tissue cells in our negative control experiments, and since there was nothing in the literature, we knew it was important to investigate further.'
Based on the finding, the fat cells we store near our skin may act as a peripheral biological clock.
Dr Light said: 'It is early days, but it is not a giant leap to suppose the light that regulates our circadian rhythm, received through our eyes, may also have the same impact through the fat cells near our skin.'
The molecular pathway they discovered was first identified as being activated by the eye when exposed to the blue wavelengths in sunlight.
He explained: 'That is why you are not supposed to look at digital devices before bed because they emit the same blue light the sun does, that signals us to wake up.
'Well, perhaps that pathway - exposure to sunlight that directs our sleep-wake patterns - may also act in a sensory manner, setting the amount of fat humans burn depending on the season. You gain weight in the winter, and then burn it off in the summer.'
This could be evolutionary process, supported by the fact that, unlike many other mammals, our fat is spread out all over our bodies just underneath our skin.
Added Dr Light: 'Our initial first observation certainly holds many fascinating clues for our team and others around the world to explore.'
'Basically what we discovered is the fat cells beneath the skin have a light sensitive pathway in them, so they can actually respond to some of the wavelengths that can pass through on a sunny day.
'Therefore, I suggest how our fat cells respond to being in sunlight may have important implications for reducing fat storage in summer months.'
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