In April's One Drop Monthly Focus, we're taking a look at Hunger. The biological nature of it, how it has evolved in our species over time, and ways to tackle those unnecessary hunger pangs. Take a look at Week 1 below, where we explore the very scientific and natural process of hunger.
What Is Hunger?
Hunger is a part of human survival.
Quite simply, it’s a signal from the brain to the body that food—or energy—is needed to keep going. It’s something that we developed hundreds of thousands of years ago as a species to keep us alive and going. But while we tend to recognize hunger as a physiological experience, it is just as much—if not more—a psychological one.
Our brains were beautifully designed to influence our eating patterns at a time when access to food was limited. These were the days in which feast or famine was regularly practiced: food would go bad quickly without any type of preservation (refrigeration), so hunter-gatherers would often stuff themselves after finding a meal-source, not knowing when they may come across the next.
These types of humans were expending energy in order to get it; they were foraging up and down mountains to catch that next energy source. At the time, hunger signaled a primal need to eat to keep bodies going. Hunger is one of our first and most innate means of survival.
How Does Hunger Happen?
That grumbling in your stomach, the knotty, almost-queasy feeling you equate with hunger is directly influenced by the hypothalamus.
The hypothalamus serves as the master control center of the body’s available energy supply (among other things). It oversees how much energy is on reserve in the body; when that threshold goes too low, the hypothalamus alerts other bodily systems to a metabolic deficit.
Eating, then, is partly stimulated (and inhibited by) these signals from the hypothalamus. This regulatory system in the brain helps ensure that your body maintains its perfect balance of energy stores, tissue needs, and other metabolic fuels—what’s known as biological homeostasis.
Within the hypothalamus is a network of neurons deeply rooted in hunger signaling. Neuropeptide Y (NPY) neurons send chemical messages to the rest of the body that stimulate a need for food intake, while the pro-opiomelanocortin (POMC) cells in that same network counteract those signals, stopping hunger in its tracks.
The brain’s network is in constant communication with other hormones found in the blood. It’s these hormones that initiate—and halt—the hunger process. Ghrelin, a hormone found in the stomach, is the chemical messenger that communicates with the brain to kickstart that appetite increase. It reduces the activity of those hunger-inhibiting cells in the brain and activates the NPY cells.
These two communication channels—one from the brain, the other found in the gut—create and continue this hunger behavior until the body is restored to its perfect energy state. Once all the body’s cells and organs are fully nourished, the hunger communication systems are halted by appetite suppression hormones, the most notable of these being leptin, though there are many others involved.
Our hunger and satiety cues are regulated by this intricately interconnected system of hormones from both the hypothalamus and the gastrointestinal (GI) tract, and their subsequent communication loops. It’s what’s known as our most basic, instinctual hunger signaling: the homeostatic hunger pathway.
But as our environment has changed, it has become more difficult to understand and balance these primal signals. Instead, a behavior-based type of hunger signaling has become much more prevalent.
Going back to those prehistoric ancestors, our bodies have evolved to crave certain concentrated sources of fat, sugar, starch, and protein. These macronutrients don’t just restore our energy levels. They also trigger the brain’s release of dopamine, the happy hormone.
In today’s food-rich environment, we are surrounded with tantalizing food advertisements that can stimulate eating, even when our energy stores our sufficiently full. It’s a challenge opposite to what our ancestors faced: our species has not evolved to face a scenario in which high-caloric food is abundant and readily available.
For the rest of this month, we’ll be focusing on ways to spot true hunger cues and ways to tackle those more sudden, reward-based urges to eat. Watch your One Drop Newsfeed for more articles on our April Monthly Focus: Hunger.