Our body is essentially a collection of clocks. The biological clock tells our bodies that it is time to sleep and also to get up. It has been established that the circadian rhythm is due to the rise and fall of a protein in our cells. The level of protein rises during the daytime, reaches its peak around evening, and its level goes down during the night time. The level of protein is an indicator of the time of the day and tells our body when to sleep or be awake. Due to the low level of protein, some of our biological processes become slower at night; our blood pressure drops and our heart rate slow.
What prompts us to get up in the morning? Satchindananda Panda studied this point precisely. He found a gene (KDM5A) that encodes a protein (JARID1a) and that, in turn, serves as an activation switch in the biochemical circuit that maintains our circadian rhythm. He observed that the flies that were genetically modified to under produce low levels of protein lost their sleep-wake track. They did not know when to sleep or wake up and took frequent naps throughout the day and night.
Sleeping and eating are two fundamental but incompatible drives. Alex Keene wanted to know whether a starved fly would take normal naps or sacrifice sleep in search of food. His observation was that flies only live a day or two when they are starved. “If they decide to sleep through the night when they’re starved, it’s a bad decision on their part. Their brains are finely tuned to suppress their sleep when they don’t have food and to sleep well after a meal.” Keene also found that genes regulate the interaction between sleep and feeding; sleep is suppressed when we are hungry. The disordered sleep-wake schedule affects not only the metabolism of flies but also of humans. Studies have shown development of prediabetic blood sugar levels in healthy volunteers due to disordered sleep. The conversion of sugars into fat, which normally occurs only at certain times of day, seems to take place all day long in diabetics’ bodies, suggesting the clock has lost control. Endocrinologist Joe Bass’s studies indicated that the metabolic rate in mutant mice differed in the way food is eaten. He observed differences in weight gain, depending upon if the food is eaten during the day or night. The mutant mice became overweight and developed diabetes. The studies on how the metabolism of fats and carbohydrates get affected by circadian clock have shown us the possibility of developing drugs that treat diabetes and obesity by targeting circadian pathways. The studies also indicate that our late-night sprees are not good for our weight loss plans. Dan Hurley has given us a timely suggestion: “Rather than focus on how much food I put in my mouth, I would focus on when I eat. I decided I would no longer eat after 10 pm.”