Our Paleolithic ancestors were well-adapted to their environment, thriving as nomadic hunter-gatherers. Their metabolism was fine-tuned through evolution to endure extended periods without food, ensuring survival.
This adaptation allowed them to function at high levels, both physically and cognitively, even in a food-deprived state. Modern humans, sharing similar physiological traits, can benefit from this evolutionary legacy. However, cultural and societal norms often prevent us from realizing this potential. The continuous consumption of carbohydrate-rich processed foods has led to a prevalence of caloric excess, obesity, and related health issues, a problem our bodies have not evolved to overcome.
The human body continually seeks a state of homeostasis, a balance where all systems perform most efficiently. To maintain this balance and survive extended periods without food, our bodies evolved a sophisticated system that signals when to eat, when to stop eating, how to process and store energy from various food sources, and when to enter a state of self-healing.
The sensation of hunger, or somatic hunger, signals when to eat. Ghrelin, a hormone produced in the stomach, and nerve signals provide the physical sensation of hunger. Limbic hunger, or your "sweet tooth," is also triggered by ghrelin and encourages the consumption of specific foods like fruits and vegetables for vitamins and nutrients. Leptin, a hormone secreted by adipose (fat) tissue, signals the body to stop feeding when it is satiated.
After a meal, the digestive tract converts food into glucose, the raw material the human body uses most readily. The pancreas produces insulin, which signals cells to absorb glucose and convert it to fuel for immediate use or to glycogen and fatty acids for storage. Three to four hours after eating, the body enters a fasting state that lasts up to eighteen hours. During this state, the body depletes glycogen stores, insulin levels decline, and a process called lipolysis begins, breaking down fat cells into smaller molecules to be used as an alternative fuel source.
After 18 hours, when all glycogen is depleted, a metabolic switch occurs where the body enters a state of ketosis and solely utilizes fat stores. The body also enters a state of self-healing called autophagy, a process of homeostasis when the body removes and recycles old or dysfunctional cells to make new cells. Limited research suggests that autophagy may play a key role in preventing or treating cancer since all cancers start from defective cells.
The domestication of livestock and agriculture that defines the Neolithic era meant humans no longer needed to expend so much energy sourcing their next meal. Farming eliminated food scarcity and created a surplus of foods higher in carbohydrates from wheat, corn, and potatoes. Unfortunately, the new diet, combined with the new-found sedentary, agrarian lifestyle, exacerbated new diseases and significantly shortened lifespans.
Compared to our ancient ancestors, modern humans enjoy a near-limitless food supply with minimal effort required to obtain it. Processed foods, intended initially to feed soldiers, gained incredible popularity in kitchens across the United States during the Great Depression. Convenient canned and pre-packaged foods augmented or replaced fresh-made meals despite being nutritionally inferior. The industrialization of food contributed to the concurrent meteoric rise in fast food popularity. However, the convenience and availability of processed foods come with a steep price to our health today.
Processed foods laden with sodium, sugar, and refined carbohydrates create a double-jeopardy when consumed. Refined carbohydrates from processed and fast food cause insulin to rise and stay elevated. At the same time, the absence of nutrients ensures the body does not stay satiated for long. Research also suggests that some additives found in processed food, such as monosodium glutamate (MSG), cause the brain to ignore leptin signals, thereby urging consumption of yet more processed foods. The uninhibited presence of insulin leads to insulin resistance and keeps the body in a constant fat storage state. Insulin resistance means the body doesn’t react as efficiently to insulin, doesn’t convert glucose into ATP as effectively, and allows glucose in the bloodstream to rise unabated. This vicious cycle is known as type-2 diabetes.
Our stress response, which is also an evolutionary holdover, operates on a feedback loop. The extended presence of glucose in the bloodstream triggers elevated blood pressure, leading to metabolic syndrome. Metabolic syndrome is the combination of obesity, insulin resistance, and high blood pressure. It is a significant risk factor for heart disease, heart attack, and heart failure. Studies link obesity and metabolic syndrome with higher incidences of colon cancer, liver cancer, multiple myeloma, non-Hodgkin’s lymphoma, gallbladder cancer, pancreatic cancer, leukemia, ovarian cancer, breast cancer, and endometrial cancer.
Research suggests that intermittent fasting can potentially prevent or correct many diseases and abnormalities, including metabolic syndrome, because it utilizes the metabolic switch acquired through hundreds of thousands of years of evolution.
Intermittent fasting (IF), which is the periodic and voluntary abstinence from food, has gained attention in recent years due to the numerous potential health benefits it confers.