When We Eat Affects Health, Weight, And Aging: Despite its relative neglect in the field of medicine, nutrition is recognized as an essential component of health. Adequate nutrient supply is necessary for reproduction, growth and maintenance, the fundamentals of any species’ survival. Paradoxically, the most powerful method for increasing lifespan is caloric restriction just short of starvation.
When We Eat Affects Health, Why?
Because nutrients are so important for survival, it makes sense that systems involved in interpreting nutrient or energy levels would play a central role in regulating reproduction, growth, and aging. In the setting of food scarcity, the dramatic increase in energy demands for mating, pregnancy and feeding a newborn are unlikely to be met. Under these circumstances, evolution selected for a longevity program that not only blocks reproductive function but promotes a stress resistant state characterized by cell protection, regeneration, and rejuvenation. Such adaptations promote survival and the maintenance of a youthful state that would allow a return to reproductive success when adequate food supply becomes available.
Recent research has identified nutrient-sensing pathways that regulate both lifespan and health span. Evolution has conserved these pathways in organisms ranging from yeast to rodents to mammals. An understanding of these pathways suggests how aging might be dramatically slowed.
This work gave birth to the many types of fasting regimens. Generally, the longer the fast, the greater the benefits. These include increased lifespan and health span, as well as a reduced risk of cancer, diabetes, and cardiovascular disease.
Time restricted feeding was an important refinement of the fasting diets. In 2012, Satchidananda Panda demonstrated that mice fed a high-fat diet eight hours per day were healthier and leaner than mice allowed to eat the same diet whenever they wanted, even though both groups consumed the same number of calories.
Chrononutrition, the coordination of eating with the body’s daily rhythms, represents the latest chapter in time restricted feeding. It must be said that while it is the latest chapter in Western medicine, the idea of chrononutrition dates back to ancient healing traditions in India and China.
We evolved on a rotating planet that created days divided into light and dark periods. The human day, until recently in our history, consisted of an active (daylight) phase and a resting (dark) phase.
This resulted in the evolution of a metabolic day shift, so to speak, bearing little resemblance to the night shift. Daytime metabolism excelled at being alert, eating, energy harvesting and storage, while night-time metabolism was designed for sleep, fasting, and accessing stored energy for regeneration and repair.
These contrasting functions are synchronized with the 24 hour day by an internal clock. In fact, every cell has a clock. These biological timepieces direct metabolism and physiology by turning on and off thousands of genes, depending on the time of day.
This means that our bodies have a preferred schedule in order to function properly. To assure daily synchrony of biology and behaviour our internal clocks must keep good time.
So how are the body clocks set?
The two most powerful regulators of our internal clocks are light and food. Light sets the central body clock in the brain and energy (food) sets the peripheral clocks.
As the sun sets, melatonin, the body’s signal of night-time, is secreted. Traditionally, melatonin was considered primarily as a sleep cue. However, in the early aughts, melatonin receptors were found on the pancreatic cells that secrete insulin. These receptors have an inhibitory effect on insulin secretion. As the sun sets and melatonin levels rise, less insulin can be released. More recent research has demonstrated that one third of the population carry a melatonin receptor gene variant that makes the pancreas even more sensitive to this insulin inhibition and is linked to higher risk for type 2 diabetes.
Melatonin is now recognized as a powerful messenger to switch from active to resting metabolic function, a chemical signal of day’s end. A robust release of this ancient hormone requires unadulterated darkness. Light, whether natural or artificial, blocks melatonin release.
Melatonin exerts its effect on weight by modulating the action of several key metabolic hormones such as insulin, ghrelin and leptin. These hormones orchestrate appetite, satiety, calorie uptake and fat storage.
Animals who have had the pineal gland (location of melatonin production) removed become overweight. Timed administration of melatonin reverses the weight gain. In addition, middle-aged fat animals given melatonin and studied to old age showed decreased weight and visceral fat. These changes were eliminated if melatonin was withheld.
Like light, food intake sets the clock to active phase. The night-time fast, like darkness, sets our clock to resting metabolic mode. Here contemporary culture and biology clash creating a social jet lag.
Disconnection from nature’s clock, circadian dyssynchrony, is now considered an important cause of our struggle with weight gain and its consequences.
Western dietary traditions are toxic to our biology. Breakfast foods such as cereals, toast, doughnuts, pancakes etc. provide a carbohydrate load when insulin levels are low. In the morning, everyone experiences a small rise in blood glucose due to low insulin, and high glucagon and cortisol. This is called the “dawn phenomenon” and occurs between 5 and 8 AM.
Dinner, the largest meal of the day, usually occurs after dark when melatonin levels are elevated. The melatonin inhibits insulin secretion resulting in impaired glucose tolerance and hyperglycemia. Persistent hyperglycemia, even if not severe, damages the eyes, kidneys, nerves, brain, and heart.
So how does this new information inform how we should eat?
· Even if practicing time restricted feeding (TRF), do not skip breakfast to prolong the fast. Early TRF, a form of intermittent fasting that involves eating early in the day, is the best way to align metabolic circadian rhythms. In addition, diet-induced thermogenesis (DIT) is twice as high after breakfast compared to after dinner. DIT is the increase in energy expenditure after a meal.) (There are 3 components of daily energy expenditure: basal metabolic rate, diet-induced thermogenesis and the cost of physical activity).
· Eat 2–3 meals per day with the last meal at 3 or 4 PM in order to have 12–16 hours of fasting and little to nothing after sunset.
· Avoid carbohydrates first thing in the morning and after sunset.
· Eliminate late night snacks
· Increase protein content of diet
42.5% of adult Americans are obese. That number climbs to 73.6% if including those who are overweight. According to the CDC, 88 million adults had prediabetes and 34 million people of all ages had diagnosed diabetes in 2018. The total direct costs of diagnosed diabetes increased from $188 billion in 2012 to $237 billion in 2017. The estimated annual health care costs of obesity are $190 billion or 21% of annual medical spending in the United States.
For the first time in history, more people are dying from eating too much rather than too little. According to the National Institutes of Health, obesity and overweight together are the second leading cause of preventable death in the U.S., just behind tobacco use. An estimated 300,000 deaths per year are due to the obesity epidemic.
One wonders when, if ever, we will acknowledge our place in nature and design a culture based on biology rather than business.
