The Hunger Demons

What to do when the body's appetite signals go haywire

It’s Friday, which means we’re almost at the end of another week of The Benedict Challenge. Starting on Monday, those who are participating will begin “18:6” fasting – 18 hours of fasting and 6 hours of eating.

For me, anything over 16 hours of fasting daily is a genuine challenge. You might be able to “white knuckle” it through one or two days of One Meal a Day per week. But fasting daily requires a different mindset. You must learn, as St. Benedict said, to love fasting.

Part of that means learning to distinguish between genuine hunger and false biological signals, the subject of today’s post. Here I should probably give a caveat that even with its health benefits, fasting can be a stressor. If you are already under a great deal of stress, you might instead focus on the discipline of prayer during Lent, while taking a more gradual approach to fasting. This is a process of discernment.

Once you are adapted, even daily fasting should not feel like a constant struggle. Yes, you will face fleeting moments of hunger (especially in the presence of food), but it should be a joyful experience on the whole. If you are trying to stick to the letter of the challenge and are daunted by the prospect of increasing the fasting window yet again, you can always modify your rule to allow yourself one or two small collations, for example.

And now, here’s a sample of the 5th chapter of the book, on hunger and hormones.

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“And after He had fasted forty days and forty nights, He then became hungry.”

–Matt. 4:2

The Gospel of Matthew informs us that after fasting for forty days and nights in the Judean desert, Jesus “became hungry.”

How hungry?

The Greek word for hunger here, prospeinos, implies painful, desperate hunger. That’s more or less what you would expect to feel after fasting for over a month. What’s strange about the wording here is not that Jesus was hungry but that it implies he wasn’t hungry for the first 39 days.

We know from stories of shipwrecked sailors and starved wanderers that the human body harbors far greater stores of energy than we credit it. A man recently survived for multiple weeks at sea with nothing but a few mustard packets.

As we saw in the last chapter, once the body shifts gears into self-consumption as fuel, hunger sensations fade. Paradoxically then, feelings of hunger actually tend to decline the longer one fasts—at least up until a point.

Very few of us face actual danger of starvation, or becoming “prospeinos.” A person with average body composition maintains enough body fat to walk from San Francisco to Los Angeles without ever stopping at In-N-Out for a snack. For most of us, it’s safe to fast for multiple days. And yet when we skip breakfast, we say, “I’m starving!”

Even Benedictine monks, despite their ancient fasting tradition, now permit breakfast after modifying their Founder’s rule.

It seems that hunger today wields disproportionate power compared to eras past, when fasting was commonplace. Jesus’ 40-day deprivation exemplified a body in tune—sensations of hunger arose only at the point of genuine metabolic need after total exhaustion of energy stores.

In contrast, modern people struggle with even a brief overnight fast—often snacking right up until bedtime and eating immediately upon waking. We seem to have lost the ability to tell legitimate hunger from fleeting cravings. Is this a moral failing? Or does it instead arise from a biological imbalance in our hunger signaling apparatus? Understanding the science of hunger can aid us in navigating our fast and distinguishing true hunger from mere cravings.

Resetting the Appestat

Scientists speak of the “gastric-brain axis”—communication between the digestive system and brain mediated by hormones that regulate hunger and satiety. The part of your unconscious brain located in your stomach connects nutrient status signals to higher brain centers, calibrating how much you eat.

In a healthy person, this cross-talk is carefully tuned to balance energy needs and storage, delivering fuel on demand through tight hormonal feedback loops. The human body has an elegant, intrinsic mechanism for regulating appetite and weight centered around this gastric-brain dialogue.

In his book The Power of Appetite Correction, Burt Herring refers to this mechanism as the “appestat.”[1] Think of a home’s thermostat and heating system. When indoor temperature dips below the defined zone, the boiler fires up to replace lost heat. Once warm air returns to the preferred range, everything switches off again until the next cycle. Our metabolism works the same way regarding fat accumulation. Its goal is keeping body fat percentage within a narrow target “set point.” If intake consistently exceeds energy needs, the appestat should dial up heat production and activity levels and reduce hunger. And during periods of deprivation, appetite should spike while metabolism slows to conserve reserves.