The connection linking sun exposure that causes you to lose body fat most likely dates back earlier than we humans could stroll upright. Way back, before the creation of video games and company cubicles, humans had to use the bulk of their time out in the weather finding food. We hunted, we gathered, and we developed a natural adaptation to the seasons. As the days shortened, our bodies instinctively understood that winter was approaching and the metabolism ground down to conserve calories. Then as spring and summer weather came around again, and food became more abundant, we came out of our semi-hibernation to start the cycle again (1). You certainly know by now that with a slowed metabolism, any thoughts to lose body fat can be thrown out the window.
This is where it will get fascinating. It appears that when we are subjected to rising levels of UV rays, our bodies activate a protection system to diminish the harm brought on by the sun. The protection is produced by escalating the amount quantity protective pigment, called eumelanin, in our skin. This increase in eumelanin is commonly recognized as tanning. This is nothing huge, the body responds to UV over exposure by tanning, but the fun doesn't stop there (2).
Amplified sun exposure leads to more than just a wholesome glow. An entire chain reaction is created that activates the most powerful substances in the human body, hormones. One of these hormones, melanocortin, also decreases desire for food, lessening appetite and performs uncoupling actions on fat cells, causing them to be broken down and used as fuel by the body and you to lose body fat. So one of the identical hormones produced by our skin when we tan, also suppresses the appetite center of our brains and makes it easier to burn body fat for fuel, causing you to lose body fat. (2,3).
An Easy Explanation
It makes a lot of sense, our hunter gatherer bodies would perceive winter coming by a shorter period of daylight. Fat serves us equally as a supply of energy during food shortage and as a thermal insulator shielding us against the frosty nights. As the weather warmed and our skin was irritated by extra sunlight, a small chain reaction was started; after all, we needed to lose body fat (that had kept us alive during the cold winter) to be more mobile and help us with the heat loss during summer. If we had not, we would have been at a disadvantage by being sluggish and prone to heat fatique during the hunt. Part of this sequence as well, melanocortin is furthermore able to ramp up your body's metabolism by causing output of thyroid hormone to amplify(3).
Here Comes Big Pharma
The hormone melanocortin can stimulate fat storage and release, the metabolic rate, and the appetite. Its manufacture is affected by the quantity of body fat stored in the body and is also involved in preserving your weight as well as getting a first-rate tan. The power of this substance is the reason many major pharmaceutical corporations have recently patented a number of novel new drugs that attempt to create the same effects. The new drugs will treat obesity, get you a tan, and treat sexual impotence as well, just in case(4).
For those who prefer the natural way, receiving just enough sun to cause a slight tan will assist you in losing weight by: lowering your appetite, helping boost your metabolism and making it easier to burn body fat for energy. Indoor tanning might have its uses after all (4).
1. Healy E, Flannagan N, et al. Melanocortin-1 receptor gene and sun sensitivity in individuals without red hair. Lancet 2000 Mar 25;355(9209):1072-3.
2. MacNeil DJ, Howard AD, et al. The role of melanocortins in body weight regulation: opportunities for the treatment of obesity. Eur J Pharmacol 2002 Apr 12;440(2-3):141-57.
3. Voisey J, van Daal A. Agouti: from mouse to man, from skin to fat. Pigment Cell Res 2002 Feb;15(1):10-8.
4. Zemel MB. Agouti/melanocortin interactions with leptin pathways in obesity. Nutr Rev 1998 Sep; 56(9):271-4.