When you feel tired for lack of sleep, it is likely due to lack of enough darkness and not necessarily due to insufficient sleep, tells the new research. How our diets and light-dark cycles have changed from what our ancestors experienced also explains why we fall ill so often.

Researchers at the National Institute of Mental Health (Bethesda, Maryland) report that 14-hour periods of darkness evokes hormonal changes. Prolactin levels are also implicated in the regulation of glucose metabolism in the liver and transport of fat in the body; as a result, less exposure to darkness causes us more prone to diabetic conditions. The same theory applies to obesity and now it seems plausible that by "resetting" prolactin levels we may be able to defuse that bulge in the middle. Or, alternately, we may chose to switch-off the light and begin to thin out by living in the darkness. One drug that is now been tested to "reset" prolactin is bromocriptine that mimics the activity of the neurotransmitter dopamine, a prolactin inhibitor. The drug has been patented for weight loss, less body fat and to alleviate the diabetic symptoms. The Phase III clinical trials are underway and if everything proves well, we may have opened a new chapter in chronobiology, the science of the effect of time on our body. The light switch may prove to be a "happiness switch."