Understanding the energy balance equation
In an era where dietary fads spread like weeds in an untended garden—keto this, vegan that, intermittent whatever—the pursuit of understanding hunger often turns into a jumble of quick fixes and commercial indulgences. Yet, at its core, hunger is not a foe to be defeated with gadgets or gimmicks but a signal from our ancient biological machinery, urging us to align with our evolutionary design. Jason Fung’s *The Hunger Code: Resetting Your Body’s Fat Thermostat in the Age of Ultra-Processed Food* (2026) provides a welcome antidote to this excess. As a nephrologist and author of the seminal *The Obesity Code*, Fung explores the metabolic roots of weight gain, reframing obesity not as a simple caloric imbalance but as a hormonal dysregulation caused by modern mismatches. This book strongly aligns with a frugal philosophy of health—one that echoes my own view of the human as a ghost within a machine: the soul navigating a metabolic engine optimized for ATP production, spiritual fulfillment, and environmental harmony. Fung’s work strips away the extravagance, focusing on essentials—managing homeostatic, hedonic, and conditioned hungers—much like tending a fire with enough correct fuel to thrive, not scorch.
Fung begins by dismantling the calorie myth, a false belief promoted by nutritional authorities despite decades of evidence disproving it. He argues that weight gain results not just from overeating, but from the body’s hormonal response to food, influenced by digestion, absorption, and timing. This aligns well with the layered metabolic systems I discussed in my previous essay, where health depends on optimizing ATP production in harmony with our origins from LUCA and LECA. Fung’s “Golden Rules”—avoid ultra-processed foods, fast regularly, and cultivate a healthy mindset and social habits—reflect the frugal principle of avoiding worldly substitutes for spiritual and physiological needs. While I highlighted spiritual hunger as the main drive, Fung expands to include three types of hunger: homeostatic (physical nutrient needs), hedonic (pleasure-seeking, often addictive), and conditioned (habitual and environmentally cued). Together, these create a comprehensive model for vitality, steering clear of costly, trendy diets and instead aligning with our ancestral patterns.
Central to Fung’s thesis is a reevaluation of the energy balance equation, which he argues is too simplistic. In a passage that clears away the fog of conventional wisdom, Fung explains:
“Understanding the energy balance equation”
The energy balance equation is a basic law of physics, known as the first law of thermodynamics, which states that energy cannot be created or destroyed. When applied to the human body, it is often called Calories In, Calories Out (CICO). The equation indicates that the change in body energy stores equals the energy we consume (Calories In) minus the energy we burn (Calories Out).
Change in body energy stores = Calories In – Calories Out.
If you consume more calories than you burn, your body’s energy stores increase. Conversely, if you consume fewer calories than you burn, your energy stores decrease. Simple, right? But this idea is so obvious that it’s almost pointless. It’s like saying that if you earn more money than you spend, your bank account will grow. While true, it doesn’t tell you how to make more money or spend less. It also doesn’t explain why some people become rich while others go bankrupt.
The equation suggests that the body is a passive container, like a balloon that inflates with more air (calories) or deflates with less. However, the human body is not passive. It actively manages body fat through a complex system of hormones and feedback mechanisms. Eating fewer calories may cause the body to burn fewer calories to compensate, maintaining energy balance. That’s why calorie restriction often fails in the long run. The real control is the body fat thermostat, set by hormones like insulin, which respond to what we eat, not just how much.
This excerpt explains why saving on health isn’t just about restraint; it needs wise fuel choices. Like our metabolic system, which evolved from symbiotic archaea and bacteria, thrives on ancient inputs, Fung’s model rejects the excessiveness of calorie-counting apps and processed “low-cal” snacks. Instead, it emphasizes hormonal harmony, similar to my support for animal-based proteins and fats absorbed in the small intestine, combined with fermented microbiota-accessible carbohydrates (MACs) for gut health. Deviations lead to problems—insulin spikes from ultra-processed foods disrupt the balance, causing chronic ATP shortages and acceleration of aging.
Building on this, Fung examines homeostatic hunger in Part 1, explaining how food’s microstructure, matrix, and preparation affect insulin release. He highlights low-insulin diets that focus on proteins, fats, and resistant starches instead of refined carbs. This aligns with my layered view of hunger: physiologic needs should be met carefully, without the distractive appeal of dopamine-driven ultra-processed foods. Consider Fung’s discussion of digestion and absorption factors, where he points out the significant influence of simple choices like food order and timing.
“The speed of absorption”
Breaking food down into its individual nutrients—digestion—is a key first step in providing the body with energy. Next, those nutrients must enter the bloodstream to reach the cells. That’s mainly the job of the small intestine through absorption. As we’ve seen, foods that are digested quickly are often absorbed quickly too, so many factors that affect digestion also influence absorption. However, the size of the foods, how they are prepared, as well as their viscosity and acidity, play a larger role in how fast they are absorbed. The way foods are served—whether plain or dressed, in what order, and at what time—also impacts absorption speed. All of these factors affect how quickly nutrients are absorbed.
“Here, Fung’s practical tips—eat carbs last, choose viscous foods like soups, incorporate acids like vinegar—embody frugality.”
The rate of gastric emptying
How quickly food leaves the stomach after digestion—gastric emptying—is a key factor in absorption. The stomach mixes what we eat with stomach acid, churns the mixture, and releases it gradually into the intestines, where nutrients are absorbed. When nutrients are released quickly, absorption happens faster. If nutrients stay longer in the stomach, absorption slows because no nutrients move into the bloodstream. Faster absorption results in a higher glucose spike and more insulin production. This effect depends on many factors, none of which are listed alongside nutrient information like calories, carbohydrates, fats, and proteins on food labels.
No need for boutique supplements; a splash of lemon juice or a side of kimchi slows glucose absorption, reducing insulin and fostering satiety. This echoes Hippocrates’ dictum, “Let food be thy medicine,” and my call to refill intracellular tanks with proper fuels, avoiding “kerosene in a gasoline engine” like processed grains and seed oils. By slowing absorption, we honor the machine’s design, preventing the fouling of the mitochondrial engine that accelerates aging and dysfunction.
Fung extends this idea to include hedonic and conditioned hungers, showing how ultra-processed foods hijack reward centers and foster addiction similar to drugs, while social environments influence habits. In a world of abundance, these hungers serve as substitutes for unmet spiritual needs, much like I mentioned with John 6:35: spiritual fulfillment reduces worldly excesses. Fung’s Golden Rule—committing to healthy social habits by surrounding oneself with supportive peers—reinforces this idea, as obesogenic environments spread norms through modeling. A frugal approach incorporates these principles: fasting intermittently to reset the system, eating ancestrally (such as steel-cut oats instead of instant potatoes for resistant starch), and syncing with circadian rhythms by eating earlier to match cortisol hormonal patterns.
Fung’s work carries subtle spiritual undercurrents, though less obvious than my explicit framing. By addressing emotional eating and mindset, he subtly acknowledges the soul’s role in hunger. Success stories in his book showcase transformations achieved not just through willpower but by understanding root causes—reflecting the stewardship I promote. Modern medicine’s focus on isolating symptoms and subsystems ignores metabolic roots; Fung, like a wise philosopher, directly targets them.
In conclusion, *The Hunger Code* is an essential companion to a frugal health philosophy. It offers the scientific framework for optimizing the body without excess, managing hunger in harmony with our evolutionary and spiritual nature. As we face a landscape of tempting excess, Fung reminds us: health is nurtured, not bought. For those seeking vitality in a world of surplus, this book is vital reading—a disciplined way to reset the thermostat and reclaim control over the body’s instincts.
