As I’ve said from the beginning, one reason so many people have been willing and able to stick with the Alternate-Day Diet is that they don’t have to diet every day. It’s about intermittent (as opposed to continuous) calorie restriction.
But again, we humans—because we’re human—tend to get bored, cheat, or let things slide when we’re doing the same thing over a long period of time. Therefore, what I propose is that, if you find that your down-day calorie intake is slowly creeping up, you’re skipping a down day here and there, or you’re just getting bored, you give yourself a break from the routine by using a different form of intermittent restriction—eating according to your natural circadian rhythm.
Virtually all living things have an innate circadian clock that determines how and when various genes and chemicals in the body are activated and interact with one another. We humans are innately diurnal, meaning that our normal circadian pattern is to be active during the day and sleep at night. Our ancestors lived in accordance with this rhythm because they didn’t really have much choice—no artificial light, no late-night TV for entertainment, and the necessity to hunt and gather food when they could see what they were doing. Now, of course, we can, and often do, turn night into day at will. But studies are beginning to indicate that this man-made disruption of our circadian rhythm may not be the healthiest way to live.
In addition to the central clock in our brains, we also have ancillary “time-keepers” in other types of cells that regulate the rise and fall of gene activity throughout a twenty-four-hour cycle. When that cycle is disrupted, we may experience a variety of metabolic dysfunctions that can cause obesity and disease.
Observational studies have shown an increase in breast cancer among night-shift workers. Changes in glucose metabolism that are associated with obesity and diabetes have been shown with a disruption of the circadian clock among pilots, and longtime exposure to artificial light has been linked to an increase in depression that can be remediated with the return to a normal circadian rhythm. The underlying reasons for these changes have not been clearly established, but there seem to be some pretty clear implications to be drawn from these observations.
Melatonin, for example, is a hormone secreted by the pineal gland that is normally released when light decreases—that is, at night. We know that increased melatonin is associated with getting a good night’s sleep, but it now appears that the proper release of melatonin at the appropriate time may also be related to other chemical processes in the body that reduce a woman’s risk for breast cancer. In fact, several studies have shown an association between increased melatonin levels and a reduction in tumor growth. Melatonin levels decrease in the absence of sleep at night and do not reach optimal growth even when the person is asleep during the day.
In addition, levels of ghrelin, the hormone associated with hunger, have been shown to go down in animals that are fed during a restricted period of time. To me, this is a significant finding because I, and others who have followed the circadian eating pattern, have experienced a reduction in appetite, particularly in the evening.
Also, many people with obesity-related Type 2 diabetes find that their diabetes goes away after gastric bypass surgery, and this may possibly be because many of the cells in the stomach and small intestine that produce ghrelin have been removed, thus reducing their hunger.
In a 2012 study published in the journal Cell Metabolism, Dr. Satchidananda Panda and his colleagues compared a group of mice on a high-fat diet who were fed only for an eight-hour period with another group fed an equal number of calories but given free access to their food. The mice on the time-restricted diet were shown to be protected against obesity, hyperinsulinemia, fatty liver, and inflammation and had improved motor coordination. The researchers concluded that a time-restricted feeding regimen was “a non-pharmacological strategy against obesity and associated diseases.”
Another study done by Drs. Oren Froy and Ruth Miskin also concluded that “circadian disruption is associated with multiple negative manifestations, whereas resetting of circadian rhythms could lead to increased longevity.”
And in February 2013, researchers at Vanderbilt University published a study in Current Biology showing that disruption of the body’s circadian rhythm can lead not only to obesity but also to an increased risk of diabetes and heart disease resulting from changes in insulin activity. “The master clock in the central nervous system drives the cycle and insulin response follows,” says Vanderbilt professor of molecular physiology Owen McGuinness. To prove their hypothesis the researchers removed one of the genes necessary for proper functioning of the biological clock in one group of mice, and found that they appeared to be locked in an insulin-resistant mode. Supplying them with the protein produced by the missing gene reestablished their circadian rhythm and reduced their insulin resistance.
In addition, they kept a group of normal mice in a constantly lit environment that also disrupted their circadian cycle (because mice, unlike humans, are nocturnal and therefore would normally eat at night) and found that this group was locked into an inactive or fasting phase during which they were naturally more insulin resistant and therefore developed a higher proportion of body fat and gained more weight on a high-fat diet than those whose circadian cycle was not artificially disrupted.
Exposure to artificial light disrupts normal circadian rhythms by reducing melatonin production, but not all artificial light is created equal, and it seems that the most harmful is blue light. An article published in the Harvard Health Letter in May 2012 states that, “While light of any kind can suppress the secretion of melatonin, blue light does so more powerfully. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6.5 hours of exposure to blue light to exposure to green light of comparable brightness. The blue light suppressed melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours).”
While in the modern world it would be difficult to avoid artificial light entirely, we can minimize our exposure to the dangers of blue light by putting filters on our computer screens and wearing glasses that block only blue light without blocking other colors as inexpensive sunglasses do. Personally, I usually wear blue-light blocking amber glasses after eight or nine o’clock at night. I do this because I believe that this simple measure will help to increase melatonin levels, which will, in turn, help to prevent disease as well as to ameliorate diseases I might already have.
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So, getting back to “giving yourself a break” by following a circadian pattern of intermittent calorie restriction, my point is that there’s more than one way to skin a cat, so to speak. Eating all your meals during an eight-hour period during the day means that you will be fasting for sixteen hours during every twenty-four-hour period. You will not only be reaping the benefits of calorie cycling without any overall reduction in your intake but you will also be accruing the health benefits derived from maintaining a robust pattern of metabolic gene expression.
My suggestion would be that if or when you feel that you need a break from the Alternate-Day Diet, you switch to the circadian pattern for a period of three weeks. During that time you can eat as much as you normally would but your entire caloric intake must be within a period of eight hours. That will probably mean skipping or delaying your breakfast and having your dinner before eight o’clock at night. The most important thing is to follow the pattern, do the same thing every day, and avoid disrupting your melatonin production by limiting your exposure to artificial blue light.
While restricting calories on your down day is the most difficult aspect of sticking to the Alternate-Day Diet, eating within this confined period of time is the challenge for most people on the circadian eating plan.
After three weeks of following the circadian plan you will probably find that you have actually lost some weight even though you have not reduced your caloric intake. I suggest that at this point you return to the alternate-day pattern, eating 30 to 50 percent of normal on the down day, which is less of a restriction than is typically suggested but will make it easier to stick to the pattern over time.
You can continue to switch from one to the other, thereby keeping yourself motivated, interested, healthy, and slim for life.