Sleep is one of the body’s ways of conserving energy. Curbing this critical resting time is linked to many metabolic derangements and fat gain.
Endocrinologists now recognize that poor sleep habits and sleep loss are risk factors for obesity and diabetes. People who sleep five or less hours per night have a 46 percent increased risk of developing diabetes compared to those who sleep seven to eight hours a night.
Other biological consequences of burning the midnight oil are insulin resistance, increased blood triglycerides, altered levels of sex and adrenal hormones, disruption of the vagus nerve, increased susceptibility to inflammation, and increased hunger, particularly for after-dinner snacks.
MEET YOUR CIRCADIAN CLOCK SYSTEM
Many crucial aspects of our metabolic and hormonal functions operate in a rhythmical fashion corresponding to the rise and fall of the sun. In fact, the word circadian is derived from the Latin words circa and dies for “around” and “day.” From primitive unicellular bacteria to complex organisms like humans, the so-called clock gene networks in these life forms align the daily rhythms of the body’s functions with the light and dark cycles of each day.
With the help of the circadian clock system, our hypothalamus matches our biology with the 24-hour cycle of the earth. This is how hormone levels, cognitive performance and body temperature peak at different times of the day. In fact many critical metabolic hormones—including insulin, cortisol, growth hormones and adrenaline—exhibit some degree of circadian rhythm. Even the hormones released from fat tissue, such as leptin and adiponectin; the hunger-inducing hormone ghrelin; metabolic hormones insulin and glucagon; inflammatory cytokines, such as TNF-alpha; the adrenal stress hormones; and melatonin. Loss of circadian rhythm of the core clock genes, or chronodisruption, is associated with obesity and diabetes.
HOW CIRCADIAN RHYTHMS REALLY WORK
The chain of communication goes something like this: The master pacemaker, the SCN, detects morning light cues and evening dark cues through nerves in the eye and transmits messages by way of the nervous system to peripheral tissues. Muscle, fat, liver, and cardiovascular tissues respond by activating or deactivating core clock genes in an oscillatory manner. This maximizes our ability to adapt to our environment
The core clock genes, which are tightly aligned with many metabolic signaling hubs, are turned on or off depending on the time of day.It’s therefore critical to a healthy metabolism to align your biological clock with the rise and fall of the sun. Stress reduction, exercise, diet, and optimal GI health are only complete when one’s circadian clock is rhythmically aligned to the external environment. Sleep and a properly tuned circadian system are paramount to shedding belly fat and attaining an optimal metabolism.
Among the well-known consequences of a disrupted circadian function are altered metabolism and even life span, which may be all adversely affected when the circadian time-keeping system is altered.”—Marta Garaulet Aza, PhD
THIS IS WHY YOU SHOULD EAT BREAKFAST
During the day, or wake phase, the pacemaker-like SCN sends messages from the brain to the periphery of the body to optimize metabolic activities with daytime functions, which include eating and movement. In circadian-aligned healthy persons, light stimulates the release of the adrenal stress hormones cortisol and catecholamine most during the morning, and this stimulation lessens as the day progresses. GI tract motility, gastric emptying, and food absorption are much more active during the day than at night. Levels of gut-hormones such as GLP-1 and CCK, are highest during the earlier part of the day, which may be why insulin sensitivity is also highest in the morning and diminishes as the day goes on.
Exposure to light also stimulates the sympathetic or “fight or flight” branch of the nervous system. The absence of light at night stimulates the parasympathetic or “rest and digest” branch of the nervous system.
Several studies have demonstrated how curtailment of this daily spike and dip in cortisol levels is linked with insulin resistance and type 2 diabetes. Researchers at Johns Hopkins University, for example, found that people with diabetes have a significantly lower rise in cortisol in the morning compared to healthy controls.
FAT BURNING OCCURS AT NIGHT
During the night cycle, the liver also increases levels of many enzymes involved in mitochondria function and lipid and cholesterol synthesis. A recent study revealed that fat burning in the mitochondria is most active during the sleep phase, peaking just before waking. At night, our master pacemaker (SCN) helps to increase fat burning (lipolysis), which has the effect of reducing hunger so that we can stay asleep. As the master pacemaker in the brain detects light, the body shifts out of a lipid-burning mode and into a more sugar-burning state.
Shiftwork increases the risk of developing fatty liver, a disease often associated with perturbed fat metabolism, increased belly fat, and metabolic syndrome. Researchers report that people with fatty livers have mitochondrial dysfunction, which impairs fat burning. Now we know that this may be a result of a skewed circadian clock.
It’s essential to get to sleep at the same time every night and to minimize both chemical and social stressors as well as light at night. “When trying to restore your natural sleep cycle, or when obligated to stay up late or travel to different time zones, take 5 mg of melatonin before bed to keep your biological clock in rhythm.
To maximize fat loss, follow the advice of lean fitness competitors: they plan their aerobic sessions first thing in the morning, so they can ride on the coattails of their natural circadian system and exploit its fat-burning potential. For maximal belly fat burning, perform interval-based aerobic training first thing in the morning on an empty stomach. Drink one to two cups of coffee or green tea prior to exercise, as caffeine helps to increase fat lipolysis burning.