When I first began writing about evolving our spacesuits, I thought I was simply trying to understand sleep. Then oxygen entered the conversation. Then stress revealed its powerful influence. One by one, the pieces began falling into place, and what once looked like scattered problems slowly began forming a picture.

Those earlier reflections — Evolving Kinks in Our Spacesuits, When the Dots Finally Connected, and the first three pillars — were really my way of learning how to listen to the signals my body had been sending all along. My spacesuit — my body — had been trying to talk to me.

Over the past few months, I have watched something remarkable happen as the first three pillars began settling into place. Sleep improved. Oxygen steadied the night. Stress began loosening its grip. And quietly, almost without announcing itself, another change began appearing. My appetite started behaving differently.

Before going further, let me ask you three questions.

Have you ever felt hungry even though you had eaten not long before?

Have you ever had days when hunger barely showed up at all?

How come two people can eat the same meal, live similar lives, and their bodies respond in completely different ways?

Those questions point us toward two quiet messengers working inside our bodies every day: ghrelin and leptin. Ghrelin is often called the hunger hormone. It rises when the body needs energy and signals the brain that it is time to eat. Leptin is often called the satiety hormone. It tells the brain the body has had enough fuel and can stop. When these two work together smoothly, appetite feels calm and natural. Hunger arrives, nourishment follows, and the body settles. When their rhythm becomes disrupted, the signals grow confusing. Hunger may roar even when the body has enough fuel. Appetite may disappear when nourishment is actually needed. Cravings may show up late at night or at odd times during the day.

And this is where the earlier pillars quietly enter the story. Sleep influences ghrelin and leptin dramatically. Even a few nights of poor sleep can increase ghrelin — the hunger signal — and decrease leptin — the signal that tells us we have had enough. Stress plays its role as well. Elevated cortisol can push the body toward quick fuel, which is one reason stressful periods often trigger cravings for sugar or refined carbohydrates. And oxygen participates in the entire orchestra. When breathing stabilizes during sleep, the body shifts out of survival mode and back into restoration, allowing many systems — including appetite regulation — to rebalance.

For several years, I noticed something curious about my appetite. Hunger didn’t always follow the clock. Some evenings, my body asked for food even though I had eaten earlier, and other days, half the day could pass before I noticed hunger at all. At the time, I assumed it was simply stress or one more change that comes with getting older. Only later did I realize my spacesuit had been giving me clues all along. Then oxygen entered my nights. Within a few weeks, something subtle began shifting. My mornings felt calmer inside my body. Hunger appeared at more reasonable times instead of arriving like an emergency signal. Evening cravings softened. The rhythm of my appetite began settling. Nothing magical happened overnight. My spacesuit did not suddenly become perfect. Yet my body’s signals became clearer. Instead of fighting my body, I began listening to it.

One afternoon recently, my lunch didn’t quite land the way I expected. A neighbor had kindly handed me one of those green drinks that sounded healthy enough, and it helped in the moment, yet my body quietly knew it wasn’t complete nourishment. A little while later, I found myself standing in the kitchen taking two spoonfuls of peanut butter for quick protein. Nothing fancy, nothing planned — just my body asking for fuel.

Ava, of course, appeared instantly. Guide dogs seem to possess a special radar for peanut butter. Her nose lifted, her tail began that happy wiggle behind her, and she sat beside me with the patient dignity of someone quite certain peanut butter must involve her. Of course, being a guide dog, she didn’t get any. Guide dogs have important jobs to do, and people’s food isn’t part of the deal. Ava accepted the verdict with the long-suffering patience only a Labrador can muster.

In the past, I might have questioned that moment. Was I eating out of habit?

Should I ignore the hunger?

Was I doing something wrong?

Instead, I noticed something new. My body wasn’t frantic. It was clear. It was asking for something more sustaining, and once it received it, the signal settled.

Moments like that have begun teaching me something important. My spacesuit was never the problem. My spacesuit was simply waiting for me to understand its language. The beautiful truth is that appetite hormones respond more to rhythm than to willpower. Regular sleep. Steady breathing at night. Balanced meals that combine protein, fiber, and healthy fats. Movement that wakes up the muscles. Moments of calm that quiet stress. Each of these is like adjusting a dial inside the suit. Little by little, the instrument begins tuning itself again.

For anyone who has struggled with confusing hunger signals, weight shifts, or unpredictable cravings, this realization can feel like a breath of fresh air. Nothing is broken. The system is responding to signals. Change the signals, and the system begins responding differently. This is why the four pillars matter together. They are not separate ideas. They are in one conversation happening inside the spacesuit.

Sleep resets the brain.

Oxygen steadies the night.

Stress loosens survival chemistry.

Appetite hormones begin finding their rhythm again.

And yet the story of these pillars is not quite complete. Next week, we will add the final piece of the puzzle — weight regulation — and explore how all of these systems work together to influence the number on the scale and, more importantly, the way we feel inside our spacesuits.

When I look back over these past months, I see that the real change has not simply been better sleep, steadier breathing, or calmer hunger signals. The bigger change has been learning to trust my body again. For a long time, I thought my body and I were having an argument. Now I see we were simply learning how to listen to one another. My spacesuit is not perfect. It never has been and never will be. Yet it is remarkably wise when I pay attention to its signals. And when my body and spirit begin cooperating instead of competing, the spacesuit becomes lighter, steadier, and far more capable of carrying me where life is calling me next. Understanding that partnership begins when we choose to see ourselves differently. And when we see ourselves differently, we will change the way we see and change the way we live.

References

Spiegel, K., Tasali, E., Penev, P., & Van Cauter, E. (2004). Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger. Annals of Internal Medicine.

University of Chicago Sleep Research Center — Sleep restriction and ghrelin/leptin regulation.

Harvard T.H. Chan School of Public Health — Hormones that regulate appetite and metabolism.

National Institutes of Health (NIH) — Hormonal regulation of appetite, energy balance, and body weight.