Busting the Biggest Myths About Energy Balance

The idea of “energy balance” has been repeated so often it feels like gospel: eat less, move more, balance the equation, and the weight will fall off. But if that were true, obesity wouldn’t be a global epidemic.

Energy balance gets thrown around like a trump card in every nutrition debate. The problem isn’t with the first law of thermodynamics — energy is always conserved. The problem is with assuming that biology behaves like physics on paper. Calories are not molecules, not hormones, not signals your body can sense. They’re a unit of heat borrowed from physics and crudely mapped onto human biology (which we covered extensively in our previous blog about Calories).

Meanwhile, your body isn’t a calculator — it’s a living system run by neuroendocrine signalling. Hormones like insulin, leptin, ghrelin, GLP-1, and cortisol decide how much you eat, how much you burn, and whether energy is stored or released.

Image Credit: Cambridge University Press

In this blog, we’ll take on six of the most common myths about energy balance (which we covered extensively in our previous blog about Energy Balance). We’ll look at the physiology, medical cases, and lived reality that completely undermine the “CICO” model. By the end, you’ll see why focusing on calorie math is not just simplistic — it’s the wrong tool for the job. Many of the common claims people make about it are either oversimplified or flat-out wrong. Let’s unpack a few of the big ones.

Myth 1: “A Calorie Deficit Always Leads to Fat Loss”

The claim: If you eat fewer calories than you burn, you must lose fat.

The reality: A calorie deficit guarantees weight loss on paper — but not necessarily fat loss in real life. Here’s why:

• The body adapts to a deficit by lowering energy expenditure (lower BMR, reduced NEAT, lower thyroid output).

• Weight loss may come from muscle and water, not just fat — especially if protein is low or resistance training is missing.

• Hormonal states like insulin resistance or hyperinsulinaemia can drive fat storage even during a caloric deficit (e.g., PCOS, hypothalamic obesity).

Physiological Explanation (Neuroendocrine Focus):

• High fat (mixed quality), high carbs from UPF, and some protein cause a super high insulin release due to rapid glucose absorption. Insulin inhibits lipolysis and promotes fat storage in adipocytes, even with a deficit (e.g., 500 kcal/day less). Low fiber (e.g., 9.7 g/1000 kcal in UPF, Hall et al., 2019) weakens GLP-1 and PYY satiety signals, increasing hunger. Dopamine surges from UPF’s palatability override hypothalamic control, sustaining intake. Leptin resistance from hyperinsulinemia further drives fat gain.

• Debunking Energy Balance: A deficit (Energy In < Energy Out) should lose fat, but insulin’s anabolic effect and disrupted neuroendocrine feedback store fat. Hall et al. (2019) showed a 0.9 ± 0.3 kg gain despite matched calories, proving quality matters.

• Medical support: Patients with hypothalamic obesity can gain fat eating as little as 500–1000 kcal/day, due to disrupted ARC signalling and very high insulin levels.

A double-blind, placebo-controlled trial of 20 subjects resulted in insulin suppression and stabilization of BMI, decreased leptin, decreased caloric intake, increased spontaneous physical activity, and improvement in quality of life commensurate with the degree of insulin suppression.

Bottom line: What matters is not just the deficit but how your body responds to it — hormonally and metabolically.

Myth 2: “If Energy In Equals Energy Out, Your Weight Must Stay Stable”

The claim: When calories in match calories out, weight must remain the same — that’s the definition of energy balance.

The reality: In certain hormonal environments, fat gain can occur even when measured energy intake matches energy expenditure:

• Diets high in refined carbs and ultra-processed foods trigger chronic hyperinsulinaemia, which inhibits hormone-sensitive lipase and blocks fat release.

• Excess glucose is converted into fat via de novo lipogenesis, even if total calories are not in surplus.

• Leptin resistance prevents satiety signals from reaching the brain, while cortisol (elevated by insulin-driven stress) increases appetite and shifts energy partitioning toward fat storage.

• Chronic hyperinsulinaemia impairs signalling in the arcuate nucleus (ARC) of the hypothalamus, sustaining fat storage even at caloric equilibrium.Cortisol and hyperinsulinaemia lower thyroid conversion (T4 → T3), reducing BMR.

• Chronic high insulin reduces NEAT (spontaneous movement), shrinking total daily expenditure.

• Over time, this neuroendocrine environment means that even if calories appear balanced on paper, less is burned and more is stored.

• The role of fructose:

  • Unlike glucose, fructose bypasses normal checkpoints and is shunted into the liver. In excess (which is abundant in SAD diet), this drives hepatic de novo lipogenesis, producing triglycerides and raising VLDL.

  • Fructose also increases uric acid, impairing mitochondrial efficiency and further lowering energy expenditure.

  • Combined with insulin resistance, fructose accelerates fat storage despite “caloric equilibrium.”

• Debunking Energy Balance: Equilibrium (Energy In = Energy Out) should maintain weight, but insulin’s dominance and neuroendocrine dysfunction drive fat gain. This aligns with insulin-resistant states.

• Medical Support: Polycystic ovary syndrome (PCOS) and Type 2 Diabetes, with insulin resistance causes fat gain on low intake or in energy balanced states due to high insulin, defying energy balance.

Bottom line: Energy balance would predict weight stability — but hormonal control can tip the scale toward fat gain even at equilibrium.

Myth 3: “If You’re in a Caloric Surplus, You Can’t Lose Fat”

The claim: If Energy In > Energy Out, fat gain is inevitable — you can’t possibly lose fat in a surplus.

The reality: Under certain hormonal conditions, the body can burn fat even with a caloric surplus. For example:

Physiological Explanation (Neuroendocrine Focus):

• With high fat (healthy), high protein, and negligible carbs, insulin release is minimal, shifting metabolism into a ketogenic state. Low insulin enhances lipolysis, breaking down fat stores into free fatty acids for energy, even with a caloric surplus (e.g., 500 kcal/day excess).

• Protein triggers glucagon, boosting fat oxidation, while ketones suppress appetite via hypothalamic neuropeptide Y (NPY) inhibition.

• Cholecystokinin (CCK) from fats/proteins signals satiety to the arcuate nucleus (ARC), reducing intake over time. Hall et al. (2021) observed initial appetite suppression on a ketogenic diet, showing neuroendocrine adaptation.

• Debunking Energy Balance: The surplus (Energy In > Energy Out) should store fat per 'Energy Balance' model, but low insulin and high fat oxidation flip this. Neuroendocrine control—insulin suppression and ketosis—drives fat loss, not calorie totals.

• Medical Support: In hypothalamic obesity, early ketogenic diets can reduce fat despite high intake by lowering insulin, contrasting energy balance predictions. A far more poignant case is of patients with Diabulimia, withhold insulin to lose weight.

No matter how much you eat, your body is essentially starving because it can’t use the food you eat for energy. This leads to a decrease in body weight.

Bottom line: Energy balance would predict fat gain in a surplus — but hormonal context (low insulin, high fat oxidation) can override the math and result in fat loss.

Myth 4: “A Calorie is a Calorie”

The claim: All calories are equal — it doesn’t matter where it comes from.

The reality: This is where the rubber hits the road. Up until now, defenders of CICO and “energy balance” might still nod along and say, “Sure, there are exceptions, but for most people, energy balance still applies. Just eat less than you burn.”

But here’s the thing: a calorie from one food source is not metabolically equivalent to a calorie from another.

Let’s break it down:

• Absorption varies: Fibre, resistant starch, some polyphenols → not fully absorbed. Two people can eat the same food, and one absorbs fewer calories.

• Excretion varies: On keto, more calories are lost as ketones in breath/urine; with high protein, more energy is lost as urea/ammonia.

• Thermic effect varies: Protein has ~20–30% TEF, carbs ~5–10%, fat ~0–3%. So 100 kcal protein = net ~70–80 kcal available. It also stimulates glucagon and growth hormone, preserves lean mass, and keeps you fuller for longer.

• Partitioning differs: Insulin, glucagon, thyroid, cortisol, and nutrient state decide whether energy goes into glycogen, fat, or immediate oxidation.

• Time of intake matters: Intermittent fasting (IF) vs grazing leads to different hormonal environments.

  • In IF/low insulin → glycogen is depleted, fat oxidation ramps up, CO₂ loss reflects fat mass leaving.

  • In high insulin (frequent eating, carb-heavy) → glycogen is topped up, lipolysis suppressed, fat burning throttled.

• Fibre: Lowers net energy absorption (5–10% of calories pass out in stool), ferments into SCFAs that improve insulin sensitivity, and boosts satiety hormones like GLP-1 and PYY.

• Refined carbs & sugar: Absorb rapidly, spike insulin, favour fat storage, and lead to a glucose crash that drives hunger soon after.

• Fat quality: Omega-3 fats are used to build cell membranes and resolve inflammation, while industrial seed oils are prone to oxidation and may trigger inflammation — two very different metabolic fates.

So: two identical “2000 kcal diets” → radically different outcomes for glycogen depletion, fat oxidation, and thus long-term weight/fat loss.

Where CICO defenders get stuck

They’ll say: “Those hormonal/partitioning effects are inside the ‘calories out’ side of the equation.” Technically true. But that’s like saying: “Yes, the weather forecast is contained within the laws of physics” — not helpful unless you can predict the weather.

It reduces to a tautology: “You didn’t lose weight because your energy out wasn’t greater than your energy in.” Which is true but unhelpful — it ignores why “energy out” differed despite identical calorie intake.

Two Meals, Same Calories — Completely Different Outcomes

Imagine these two 500 kcal meals:

• Meal A: Grilled salmon, broccoli, olive oil (protein, fibre, healthy fat)

• Meal B: Donut and soda (refined carbs, sugar, industrial fat)

Both have the same caloric value, but Meal A:

• Burns more calories during digestion (higher TEF)

• Keeps you fuller longer (satiety hormones engaged)

• Keeps insulin lower, allowing fat burning to continue

• Preserves lean mass and metabolic rate

Meal B, meanwhile:

• Burns almost nothing during digestion (low TEF)

• Spikes insulin, switching off fat burning

• Leads to a blood sugar crash that increases hunger

• Encourages over-eating later in the day

Same calories, opposite hormonal and metabolic outcomes.

Why This Matters

This isn’t just an “edge case” for a tiny minority — this is the reality for everyone. Calorie quality changes TEF, satiety signalling, insulin dynamics, and even how much of the calorie actually reaches your bloodstream.

So when someone says “just eat less,” what they really should be saying is “eat differently” — because the right foods will naturally lower appetite, raise energy expenditure, and make “eating less” almost effortless.

Image Credit: Bryn Arata Nutrition

Same Calories, Different Metabolic Outcomes

Whole / Minimally Processed Food	Ultra-Processed Food (UPF)	Absorption & Net Energy	Hormonal / Metabolic Fate
Grilled salmon (150 kcal, ~20g protein, healthy fats)	Sugary cereal with skim milk (150 kcal, mostly refined carbs)	Salmon: high thermic effect (20–30 kcal lost in digestion), slower absorption.	Protein + omega-3s preserve lean mass, lower inflammation, keep insulin low, promote fat oxidation. Cereal spikes insulin, lowers satiety, encourages fat storage.
Apple (95 kcal, fibre + polyphenols)	Apple juice (95 kcal, no fibre)	Whole apple: ~20% of energy lost via fibre fermentation, slower glucose release.	Triggers satiety hormones (GLP-1, PYY), stable blood sugar. Juice hits bloodstream fast, spikes insulin, hunger rebounds quickly.
Lentils (200 kcal, protein + fibre-rich carbs)	White bread (200 kcal, refined carbs)	Lentils: slower digestion, some calories lost in fibre, ~30 kcal used in TEF.	Improves gut microbiome, lower insulin response, promotes fullness. Bread: rapid absorption, higher insulin spike, encourages fat storage.
Mixed nuts (180 kcal, healthy fats + fibre)	Potato chips (180 kcal, refined starch + oil)	Nuts: up to 20% of fat calories not absorbed (exit in stool).	Satiety hormones released, stable blood sugar, supports heart health. Chips: near-total absorption, low TEF, reward pathways triggered → over-eating.
Greek yoghurt (120 kcal, protein + probiotics)	Ice cream (120 kcal, sugar + fat)	Yoghurt: ~15 kcal lost in TEF, protein boosts satiety, probiotics aid gut.	Preserves lean mass, stable appetite. Ice cream: sugar-fat combo drives dopamine reward, weak satiety → overeating risk.

Key Insight

• On a label, the numbers look the same.

• In your body, they behave completely differently.

Fibre, protein, fat quality, and food structure all influence how much energy is absorbed, how much is burned during digestion, and whether it ends up stored or burned.

This is why “a calorie is a calorie” fails in practice.

And if a calorie is not a calorie — if we can’t reliably know how much of it is absorbed, how much is lost in digestion, and what its metabolic fate will be — then how would anyone know how many calories to cut?

Are people expected to constantly battle with calorie math, obsess over every bite, track every number on an app, and then feel guilty for “going over” — even though the body never sees those calories the way the food label does?

The truth is, the body doesn’t run on the maths of food labels. It runs on hormones, enzymes, gut signalling, and metabolic context. That’s why sustainable weight loss isn’t about counting calories harder — it’s about choosing foods that let your biology do the 'counting' for you.

Myth 5: “Energy Balance Is the Ultimate Driver — Hormones Don’t Matter”

The claim: Hormones are just downstream, and energy balance still rules.

The reality: Hormones don’t just change behaviour — they change partitioning of energy:

• Insulin actively shuttles energy into fat cells and blocks fat release.

• Leptin signals how much fat you have stored and adjusts metabolic rate accordingly.

• Cortisol shifts energy toward visceral fat storage under stress.

This means two people with identical calorie intake and expenditure can end up with completely different fat-loss outcomes depending on their hormonal state.

Myth 6: “Energy Balance Is a Lever You Can Control”

The claim: Just eat 500 fewer calories and you’ll lose 0.5 kg per week — easy!

The reality: The body fights back:

• Your metabolic rate drops (adaptive thermogenesis).

• You unconsciously move less (lower NEAT).

• Hunger hormones ramp up, making it harder to stick to the deficit.

That “500 kcal/day deficit” can shrink to near zero in a few weeks — without you changing anything.

How a 500 kcal/day Deficit Shrinks Due to Physiological Adaptations

When you cut calories to create a deficit, the body adapts by reducing energy expenditure, making the deficit smaller over time. This table illustrates a real-life example of a person starting a 500 kcal/day deficit and how physiological changes—driven by neuroendocrine signals—can shrink that deficit to near zero within weeks, without any conscious changes to diet or activity.

Week	Energy In (kcal/day)	Energy Out (kcal/day)	Deficit (kcal/day)	Physiological Adaptations	Key Hormonal/Neuroendocrine Drivers
Baseline	2500 (maintenance)	2500 (BMR: 1600, NEAT: 700, TEF: 200)	0	Normal metabolism, no restrictions.	Stable insulin, leptin, ghrelin, and thyroid (T3) levels.
Week 1	2000 (500 kcal cut)	2400 (BMR: 1550, NEAT: 650, TEF: 200)	400	Early adaptation begins. Body senses lower energy intake, slightly reducing BMR and NEAT to conserve energy.	Ghrelin rises, signaling hunger. Thyroid (T3) begins to decline, slowing metabolism.
Week 2	2000	2250 (BMR: 1450, NEAT: 600, TEF: 200)	250	Adaptive thermogenesis intensifies. BMR drops further due to reduced thyroid output. NEAT decreases as spontaneous movement (e.g., fidgeting, walking) subconsciously declines.	Leptin falls due to lower fat stores, increasing appetite. Cortisol rises, promoting energy conservation.
Week 3	2000	2100 (BMR: 1350, NEAT: 550, TEF: 200)	100	Significant metabolic slowdown. Muscle efficiency increases, reducing energy cost of movement. Hunger spikes, making diet adherence harder.	Ghrelin peaks, driving cravings. Low T3 reduces BMR. Insulin sensitivity shifts, favoring fat storage.
Week 4	2000	2050 (BMR: 1300, NEAT: 550, TEF: 200)	50	Deficit nearly gone. Body prioritizes energy conservation, minimizing fat loss. Immune and reproductive hormones may also downregulate, further lowering expenditure.	Leptin resistance emerges, reducing satiety. Cortisol sustains hunger and fat retention.

The Takeaway

Energy balance is real — but it’s a result, not a strategy. Focusing only on “eat less, move more” is like focusing on your car’s fuel gauge while ignoring the throttle, engine efficiency, and leaks in the tank. Calorie counting assumes a static system, but the body’s neuroendocrine responses dynamically adjust energy expenditure, rendering deficits unsustainable without addressing food quality, stress, and sleep to stabilize hormones.

Conclusion: Beyond the Energy Balance Illusion

We’ve dismantled six of the most common myths propping up the “energy balance” narrative. Yes, energy is conserved — but biology decides how that energy is partitioned, absorbed, burned, or stored. Hormones, gut signals, and neuroendocrine feedback loops — not calorie math — determine whether you feel hungry, satisfied, sluggish, or energetic.

The success of weight-loss drugs, metabolic surgeries, and dietary shifts all prove the same point: fat loss happens when biology is nudged in the right direction, not when people simply “try harder” with calorie counting. Energy balance is the scoreboard, not the playbook.

This means the real path forward is not obsessing over every number on a food label, but learning how to eat, move, sleep, and live in ways that work with your body’s signalling system instead of against it.

Calories may explain the physics — but hormones explain the outcome. And if you want lasting results, it’s time to put biology, not arithmetic, back at the centre of weight control.