Casting Out Appetite Gremlins
When to ignore the body's hunger signals
Just before the start of his ministry, Jesus was led up into the wilderness to fast, and be tempted by the devil:
“And after He had fasted forty days and forty nights, He then became hungry (prospeinos)." (Matt. 4:2)
The wording of this verse in the Gospel of Matthew is informative. It implies that prior to the 40th night, Jesus wasn’t hungry—or at least not starving.
Paradoxically, hunger seems to go down, not up, the longer one fasts—at least up until a point. Once the body shifts to using fat for fuel, we discover we have far more accessible energy in reserve than we realized when relying on three meals a day, plus snacking.
Hunger is a complex phenomenon. We say “I’m starving” when a few hours have past since our last meal. In fact, most of us are weeks away from true starvation given the adipose tissue we carry in reserve. This is not to diminish feelings of hunger which can cut short our fasting efforts if we don’t understand what’s happening both physically and mentally.
As we continue to lengthen our fasting window from 14 hours to 16 hours this week, I want to talk about different kinds of hunger and the underlying mechanisms that drive them so that we can distinguish between “prospeinos”—true hunger, bordering on starvation—from other kinds of hunger that we are better off ignoring.
The Minnesota Starvation Experiment – How to Starve Yourself While Constantly Eating
In the 1940s, Ancel Keyes [1] conducted a study known as The Minnesota Starvation Experiment, which provides a perfect example of how not to fast.
Subjects in the year-long study—men ages 20-33—were put on a diet that mimicked the post-WWII conditions in Europe. For six months, they were given a semi-starvation diet of ~1,500 calories per day of “rations” consisting only of foods that were available in countries that had been devastated by the war: potatoes, bread, jam, sugar, cabbage salad, jello, oatmeal, macaroni and the like.
The frequent but undersized and nutrient-void meals kept the body from ever making the transition into ketosis. Instead of efficient fat burning, the men remained stuck in the less efficient intermediate process of gluconeogenesis. Combine this with a caloric deficit, and their bodies would have no choice but to a) shut down or b) cannibalize their own protein stores to meet their energy needs.
The results of this semi-starvation were predictable. Participants were always hungry. They couldn’t control their body temperature and lost coordination. Their appearance suffered, as did sex drive and energy levels. When they were finally allowed to eat again, many of the men binged on 10,000 calories or more per day. This study was recently replicated with similar results.
This vicious cycle plays out as millions of Americans attempt weight loss through short-term “yo-yo” dieting that changes portion sizes but never underlying habits.
Understanding the appestat & different kinds of hunger
The failure of most diets, in the long run, stems from the body's unwillingness to starve itself. Appetite is an ancient survival mechanism without which we would not be motivated to seek out food when it’s needed. For thousands of years, obesity was nonexistent in humans, suggesting this mechanism was finely tuned for survival.
Drugs like Ozempic™ work by overriding our natural appetite signals, but the drug’s long list of side effects suggests this comes at the expense of malnutrition. As Keyes’s study showed, we suffer without proper nutrition. The dreaded “starvation mode” people talk about is just a long-term response to a caloric deficit, where your body's hormones start to signal the need to conserve energy. This can lead to feelings of being constantly cold, having low energy and, of course, being hungry.
However, we must distinguish true biological hunger—or starvation in extreme cases—from fleeting hunger sensations that trick the brain into thinking we need to eat when our energy needs can easily be met with existing fuel stores. Hunger is not starvation. Our appetite, or momentary hunger, is conditioned by a different set of hormones than do-or-die starvation mode.
In his book The Power of Appetite Correction, Burt Herring compares the body's hormonal hunger signals to a thermostat regulating a house's temperature. The “appestat” controls how much fuel we burn to maintain adequate fat stores in emergencies. In Herring's analogy, body fat percentage represents temperature, hovering within a small range around a “set point” largely beyond our control. Whereas true hunger comes from the body, appestat-driven eating emerges from within the brain core. It overrides conscious preferences. It's instinctive.
If your appestat gets out of balance—even by 20 calories a day—it will lead to an annual surplus of about 7,000 calories, or two pounds of body fat. If people could solve their weight gain by eating 20 calories fewer per day, it suggests that there’s more to the problem than a lack of willpower. When the appestat is broken, the advice to “exercise more, eat less” is useless. Rather than setting unrealistic goals, we must refocus on the underlying systems that drive outcomes. We must address this hormonal imbalance.
The Appetite Gremlins
In the last post, we looked at the role of insulin in promoting a vicious cycle of cravings. Insulin spikes from frequent snacking or carb-rich meals set us up for a blood sugar crash, which makes us reach for another snack. It helps to have at least a cursory understanding of hormones like insulin, but we don’t need to identify all of the precise factors in our modern environment that are conspiring to make us fat, sick, and lazy. Herring refers to the complex forces disrupting our appestat control as “appetite gremlins.”
“Gremlins,” Herring writes, “Have been blamed for things going wrong in all sorts of vehicles since the 1940s, especially things that had no clear explanation.”
The blessings of technology sometimes backfire, and we are left to sort through a mess of complicated possible reasons for the sudden rise in obesity – none of which have to do with an inherent weakness of humanity or genetic flaw.
Here are a few examples:
Cultivation of sugar-rich foods: sweeteners like honey used to be extremely scarce. The only place you could find sugar was naturally, in fruit. But today, even the fruit has been genetically modified to be bigger and juicier. The same goes for starches like potatoes, not to mention the abundant availability of bread and staple grains—subsidized by Uncle Sam.
Processed foods: We can buy bags of shelled, roasted nuts without having to pick them, crack the shells and then prepare them in a way that makes them edible. Convenience stores entice us with hyper-palatable candy bars, engineered with the perfect ratios of sugar, fat, salt, and additives to be maximally addictive (and minimally satiating).
Blue light late at night: We are surrounded by artificial blue light from our screens and televisions at all hours of the day, disrupting our natural circadian rhythm and causing all kinds of mayhem at the level of our hormones.
Social occasions: From potlucks to children’s birthdays, we are always coming up with reasons to “celebrate” with sweet desserts at times when we would never think to indulge by ourselves.
The overarching problem is the profound mismatch between our natural physiology and the modern environment. It is truly a crisis of abundance.
Herring chooses the gremlins metaphor, but since this is the Benedict Challenge, let’s go ahead and acknowledge that the modern world is full of demonic forces. We don’t need to know all of the demons or gremlins by name to engage in effective spiritual warfare. Instead of trying to isolate a single root cause of our maladies, we must find a fix that disempowers them all simultaneously.
Looking Under the Hood: Hunger Types
Warning: This section gets somewhat technical and is only for those who are interested in what’s going on underneath the hood.
Obesity researchers have discovered a “gastric-brain communication,” meaning the part of your unconscious brain located in your stomach. These hormones connect your body's signals to your brain about how much you should eat. In a healthy person, hormonal signals are carefully calibrated to balance your energy needs and storage, delivering energy where it’s most needed.
Diets fail long-term because they limit how much we can eat when our body thinks it’s starving. However, in the short run, we can use our limited willpower to limit when we eat rather than how much. By delaying meals, we can resensitize the hormones responsible for inappropriate feelings of hunger and expel the appetite gremlins permanently.
The Tl;dr version (Too Long; Didn’t Read) is that the appetite gremlins do most of their mischief by dysregulating three hormones: insulin, ghrelin, and leptin.
For most of us, 40 days of fasting would bring us close to starving, but the shorter fasts we’re talking about during Lent won’t get us anywhere near starvation from fasting, unless we attempted an extended fast with a low initial body fat level.
Limbic hunger refers to the drive to keep eating until you feel full. I call this ‘Pringles hunger,” i.e., “Once you pop, you can't stop.” This is why limiting snacking is wise and why One Meal a Day is a proven method of controlling appetite—once you adapt.
There’s also somatic hunger – stomach rumbling – that we feel physically. Clock hunger, based on routine, is a type of somatic hunger. When you wake up, if you're accustomed to eating breakfast, you’ll feel hungry. This is primarily driven by ghrelin, the “hunger hormone” produced in the gut. Ghrelin is essential for regulating balanced energy levels. It adjusts how much energy goes toward making ATP (for immediate use) versus storing fat, glycogen, or releasing heat. Ghrelin levels rise sharply after waking, acting like an alarm clock. Your body prepares to eat, and the ghrelin spike boosts your motivation to find food. Ghrelin falls after meals, but also falls naturally if you can ride out the wave of initial morning hunger.
Ghrelin closely relates to leptin, the “master regulator of body fat.” Leptin communicates your body’s levels of fat stores to your hypothalamus in the brain, which regulates hunger and satiety. When fat stores are low, ghrelin rises and leptin falls, increasing appetite and food intake. When fat stores are high, leptin increases and ghrelin decreases, reducing appetite and eating. Again, this feedback loop helps maintain stable body weight and fat over the long term.
In healthy people with sufficient stored body fat, leptin signaling should be strong enough to turn off the alarm clock and tell you to eat less. It should function as a built-in automatic stabilizer for body weight. For example, if you eat ice cream and birthday cake one day, you'll burn more energy the next day. Your appestat will dial up activity in response to the presence of more energy.
However, chronically high leptin levels desensitize the brain to the signal, so that it takes more food just to feel full. This is called leptin resistance—the evil twin sister of insulin resistance. The brain becomes unresponsive and thinks that there's too little leptin, when in fact, there's plenty of fat stored on your body. Intermittent fasting helps to resensitize, or “reset” leptin.
Into Week 5—16:8
To summarize, resetting hormonal functioning is the key to mastering your hunger and appetite. The causes of hormonal dysfunction are legion, and we don’t need to understand exactly where the problem lies in order to fix it.
Resensitizing your hormones is a process that can take months if you only change your diet (for example, eating more nutritious fats and fewer empty carbs and unhealthy fats). However, fasting accelerates this process. Think of it like turning the computer on and then off again.
Unlike a diet, which obsessively tracks calories, we focus on fixing the underlying system where appetite gremlins are wreaking their havoc. If your appestat control is working, you shouldn't have to constantly track calories to stay at a healthy weight. Furthermore, by resensitizing hormones like leptin and ghrelin, you also regain the ability to enjoy food and feel full.
This week, we move one step closer to OMAD with so-called 16:8 fasting – 16-hour fasts followed by an 8-hour eating window. When you encounter hunger this week, just remember that it is fleeting.
“And after you have suffered a little while, the God of all grace, who has called you to his eternal glory in Christ, will himself restore, confirm, strengthen, and establish you.”
1 Peter 5:10
[1] Keyes is best known for his later work, promoting low-fat, high-carb diets that informed the USDA’s woefully misguided food pyramid. Ironically, the diet he ended up advocating was not so far off the diet of the men in the semi-starvation study. We are still suffering from his legacy of cherry-picking and confirmation bias when it comes to the conventional wisdom about carbs and fat.