Seeking Light in the Refrigerator

The effect of decreasing daylight on weight

Posted Oct 10, 2012

There is no denying that the days are getting shorter. In less than a month, we will be turning the clocks back to standard time and beginning to count the days to summer. If you live in the southernmost States, the decrease in the ratio of light hours to dark is noticeable, but has little effect on eating, mood, physical activity or attention span. As one moves further north, however, waking up in the dark, leaving work in the dark, and encountering gloomy, cloudy, overcast skies at lunchtime may have a dramatic effect on one’s quality of life. The negative cluster of mood, appetite and energy changes are known as Seasonal Affective Disorder or SAD.

Tiredness is one of the first symptoms of SAD, and is often explained away as early flu, too much work, or too little sleep. While it could be all of the above, more likely, it is SAD. The body feels heavy and weighed down, it becomes harder to summon energy to continue the same exercise routine or household chores, and curling up on a couch seems much more preferable to going to the gym or raking leaves. The rest of the symptoms appear: excessive sleepiness, the desire to eat only carbohydrates, disinterest in work and social activities, and finally, depression. We may feel like grumpy bears getting ready to hibernate but unlike the bears, we cannot crawl into a cave and retreat from daily life until the daffodils bloom.

While one might counter with the good news that we may decrease our chance of getting skin cancer from sun exposure, the bad news is that we find it very hard to carry on the same level of work performance, social activities, physical activity and control of food intake as we did during the long, sunny days of Summer.

Not everyone suffers from SAD or its milder variant, the winter blues. The most intense symptoms tend to be felt in the more sparsely populated northern latitudes, in places such as Alaska or northernmost Canada. But pick a conversation about early darkness right after we switch to standard time and you are likely to hear most complain about restricting activity when it is dark by 4:30, crawling into bed at 8 pm and most common, abandoning any attempts to lose weight.

Snowbirds, that species of humans who migrate to southern climates during the winter, know the healing power of long hours of sunlight. People stuck in the northern states reproduce this by sitting in front of special light boxes in the early morning to make their brain think it is still July. Light has been available since the late 1980s. While it does improve mood and restores interest in work and social life, it has little or no effect on controlling appetite. The same is true of the antidepressants which are often prescribed for the depression of winter. Indeed since so many antidepressants cause weight gain, they may be adding to the problem, although they are of course effective in combating depressed mood.

Changes in food intake from summer to winter can be astonishingly high. Several years ago, we invited volunteers to live for several days in an MIT Clinical Research Center during late fall and then again mid-May. They ate freely from a variety of meal and snack foods during their stays. We found that they consumed about 1,300 calories more each day in November than in late-spring. Even though all the participants complained about weight gain during previous years, none of them realized how much more they were eating during the dark seasons. It was as one of them told us, “…As if I am seeking light in the refrigerator.”

All of the research subjects craved carbohydrates, which points to inactive serotonin as involved in the mood and appetite symptoms of this winter depression. Seeing that the brain can only make new serotonin to boost the inactive neurotransmitter already in the brain after sweet or starchy carbohydrates are consumed, it seems to prompt these winter depressives into consuming the correct foods by making them crave them. Unfortunately the craving signal does not come with instructions as to which carbohydrates should be eaten and in what amounts (less than five grams of protein and fat). One volunteer used to go to bed every day at 5 p.m. with a bag of cookies, a bag of potato chips and a large bottle of soda. Her weight gain was no surprise.

Fortunately, there are alternatives to cookies and potato chips and soda. We have found that small amounts of fat-free carbohydrates like rice cakes, unadorned baked potatoes, shredded wheat squares and steamed rice have the same effect of the brain as their fat-filled carbohydrate cousins. Moreover since serotonin exerts control over non-hunger type eating; i.e. nibbling and munching, once enough carbohydrate is eaten to raise serotonin levels, a sense of fullness and satiety is felt. So a dinner of a baked sweet potato or pasta with steamed vegetables and a sprinkling of grated cheese will have the same effect on controlling hunger and improving mood as French fried potatoes, cheese drenched Nachos or pizza coated with cheese and olive oil…and the former options will not result in weight gain.

Protein, fruits, vegetables, and low fat dairy products must also be eaten, but are probably better tolerated earlier in the day when mood and cravings are bearable. If protein is eaten along with carbohydrate, no serotonin is made; thus suggesting that someone with SAD follow a high-protein diet to improve mood and control weight will be as effective as building a snowman in Texas in August.

Years ago, when I was invited to a conference on SAD in northern Sweden in early fall, a participant told me that in his town people tended to eat potato sandwiches during the winter. It makes sense from a serotonin synthesis point of view but I am still waiting to see it featured on the Food Network.

Forewarned is forearmed, and now is the time to naturally boost your mood to keep the winter blues at bay.

More Posts