Two Papers, One Error: A Category Mistake at the Foundation of the ISSN Diet Literature

1. Introduction

The International Society of Sports Nutrition (ISSN) has published two documents that bear directly on the framework used to understand body weight regulation. The first is a position stand on diets for body weight reduction [1]. The second is a review of common questions and misconceptions about diets [2]. Both are substantial contributions. The position stand synthesizes the evidence on weight reduction diets across 15 consensus points. The review addresses sixteen common questions with detailed empirical evidence. Both are well-referenced, specific, and aimed at practitioners working with active individuals. Yet both contain the same category error at their foundation.

This commentary is not a critique of the empirical content of either document. It is an observation about a category error that appears in both, and about the logical contradictions that follow from it. The error is stated explicitly in the position stand and implicitly in the review. It is not a minor detail. It shapes every recommendation, every interpretation, and every conclusion.

The error is this: both documents treat a derived quantity as though it were primary. The derived quantity is energy. The primary quantity is mass. The human body does not handle energy. It handles mass – grams of protein, fat, and carbohydrate; grams of tissue gained or lost. Energy is a computed property of that mass. It is calculated from mass measurements using conversion coefficients.

When a derived quantity is treated as primary, the framework does not match the content. When the framework does not match the content, logical contradictions follow. They are not incidental. They are structural.

This is a particularly acute problem for the ISSN’s intended audience. Sports nutrition practitioners do not work in energy. They work in mass. A coach who tells an athlete to consume 2 grams of protein per kilogram is working in grams. A coach who tells an athlete to consume 3000 calories is working in a derived quantity. The ISSN’s own recommendations are in grams. Its framework is in calories. The mismatch is not abstract. It is practical.

2. Paper 1: The Axiom That Isn’t

The position stand opens with the following claim:

“For the goal of weight loss, it is axiomatic that hypoenergetic (negative energy balance; caloric deficit) conditions must be sustained.”

The word “axiom” has a precise meaning in mathematics and logic. An axiom is a proposition that is self-evidently true and requires no proof. Euclid’s parallel postulate is an axiom. The law of non-contradiction is an axiom. 1 + 1 = 2 is not an axiom – it is a theorem derived from axioms.

The caloric deficit is not an axiom. It is a derived quantity:

$$D=E_{\mathrm{in}}-E_{\mathrm{out}}$$

where E_in is calculated from mass measurements (grams of food) using conversion coefficients, and E_out is calculated from CO₂ production (a mass flux) using the Weir equation. Both terms are derived. The caloric deficit is therefore a second-order derived quantity – a computed value built on assumptions and conversions.

A derived quantity cannot be an axiom. It requires proof, not self-evidence.

What is self-evident is something else:

$$M_{\mathrm{in}}-M_{\mathrm{out}}=\mathrm{\Delta }M$$

Mass in minus mass out equals mass change. This is conservation of mass. It is arithmetic. It requires no conversion, no coefficient, and no assumption. It is the same kind of statement as 1 + 1 = 2 – a theorem derived from the definition of mass.

The position stand does not state this. It states that the caloric deficit is axiomatic. The document’s own figure reinforces this: it presents an “energy deficit” spectrum – VLED, LED, moderate deficit, non-VLED – with no “mass deficit” spectrum alongside it.

The framework is stated visually before it is stated verbally. The framework is energy.

3. Paper 2: The Same Error in Three New Forms

The review repeats the same error in three additional forms. Each is presented below with a formal analysis.

3.1. The First Law of Thermodynamics Is Silent on Mass

The review states:

“This fundamental concept, known as the energy balance model, is based on the First Law of thermodynamics, which states that energy cannot be created or destroyed, but only converted or stored.”

The First Law of Thermodynamics is the law of energy conservation. It concerns energy. It says nothing about mass [3].

This is not a technicality. It is the central point. The review invokes the First Law to justify a framework in which mass is treated as derived from energy. The First Law is silent on mass. It does not say that mass is derived. It does not say that mass is primary. It does not say anything about mass at all.

Mass has its own conservation law:

$$M_{\mathrm{in}}-M_{\mathrm{out}}=\mathrm{\Delta }M$$

This is arithmetic, not thermodynamics. It requires no conversion, no coefficient, and no assumption. It is self-evident in the same way that 1 + 1 = 2 is self-evident.

Formal analysis:

1. The First Law of Thermodynamics concerns energy conservation. (Physics)

2. A law concerning energy conservation says nothing about mass. (Definition)

3. The energy balance model treats mass as derived from energy. (Framework)

4. A law that is silent on mass cannot establish that mass is derived. (From 2 and 3)

5. Therefore, the First Law does not support the energy balance model. (From 4)

The contradiction: The review cites a law about energy to justify a framework that makes a claim about mass. The law is silent on the claim. It does not say that mass is derived from energy.

The mass balance framework predicts: Mass has its own conservation law. It is primary because it is what is measured. Energy is derived from mass through conversion coefficients. The two laws are distinct. The First Law does not bear on mass conservation.

3.2. Protein Must Be Calculated in Grams, Not Percentages

The review states:

“Critically, expressing protein intake as a fixed percentage can result in underconsumption, especially in hypocaloric diets. For example, a 70-kg individual on a 1600 kcal/day diet consuming 15% of energy from protein would only ingest 60 g of protein, far below the ISSN minimum of 98 g/day.”

Formal analysis:

1. If energy is primary, protein intake can be expressed as a percentage of energy. (Premise from EBM)

2. If protein can be expressed as a percentage, a percentage is a sufficient guideline. (From 1)

3. The review states that a percentage is not sufficient – it leads to underconsumption. (Textual fact)

4. Claims 2 and 3 are in conflict. (From 2 and 3)

The contradiction: If energy is primary, protein should be expressible as a percentage. The review demonstrates that protein must be expressed in grams. This is a mass-based argument that defeats its own framework.

The mass balance framework predicts: Protein mass is primary – in grams. Energy is a derived quantity, calculated from mass. The review’s own argument is the MBM argument.

3.3. Weight Loss Without Caloric Restriction – but the Mechanism Is Explained in Energy

The review states:

“However, research indicates that significant body weight reduction can also occur without explicit caloric restriction by manipulating dietary macronutrient distribution, particularly by changing protein and carbohydrate intake.”

And it presents several studies in support:

- Pescari et al. (2024): LCD, KD, and HPD produced greater weight loss than calorie-restricted diets

- Wycherley et al. (2012): HPD produced greater fat loss without significant caloric difference

- Skov et al. (1999): High-protein, low-carbohydrate diet produced 8.9 kg vs. 5.1 kg

The review then explains these findings through “satiety” and “thermic effect.”

Formal analysis:

1. If energy is primary, weight loss requires a caloric deficit. (Premise from EBM)

2. The review presents studies in which weight loss occurred without a caloric deficit. (Empirical evidence)

3. Claims 1 and 2 are in conflict. (From 1 and 2)

4. The review explains the conflict with “satiety” and “thermic effect.” (Textual fact)

5. These mechanisms are mass-based: protein mass determines satiety, which determines mass intake. (From 5 and mass balance)

The contradiction: The review presents mass-based findings and explains them with mass-based mechanisms – but the framework is energy.

The mass balance framework predicts: Weight loss occurs when mass outflow exceeds mass inflow. Protein mass (in grams) determines satiety and therefore mass inflow. The findings are exactly what MBM predicts.

4. The Pattern

Across both documents, the same structural pattern appears. In each case, the quantity that is measured is mass, but the quantity that is analyzed is energy. The mismatch is not incidental. It produces the contradictions described above.

The pattern can be stated in four propositions.

First, the position stand measures mass deficits but describes them as an “axiomatic” caloric deficit. The measured quantity is mass. The analytical quantity is a derived value. The category error is that a derived quantity has been treated as an axiom.

Second, the review measures mass conservation but justifies its framework by the First Law of Thermodynamics. The law that is invoked concerns energy. The quantity that is conserved is mass. The category error is that a law of one kind has been invoked to support a claim about a different kind.

Third, the review measures protein in grams but presents it as a percentage of energy. The measured quantity is mass. The analytical quantity is a derived ratio. The category error is that a mass quantity has been expressed as an energy quantity.

Fourth, the review measures mass fluxes but describes them as a caloric deficit. The measured quantity is mass. The analytical quantity is a derived value. The category error is that a mass phenomenon has been explained in energy terms.

In each case, the pattern is the same: the measured quantity is mass, the framework is energy, and the contradiction follows directly from the mismatch.

The deepest form of the error appears in the review’s citation of the First Law. The First Law is a statement about energy. It says nothing about mass. Yet it is cited to justify a framework in which mass is treated as derived from energy. This is not a technical error. It is a category mistake: a law of one kind has been invoked to answer a question of a different kind.

5. Why This Matters for the Intended Audience

Both documents are substantial contributions. They synthesize evidence, provide practical guidance, and will be useful to coaches, athletes, and sports nutrition practitioners. Yet their framework does not match their content. The position stand calls a derived quantity axiomatic. The review invokes the First Law of Thermodynamics to justify a claim that the First Law does not address. Both express mass quantities in energy terms and then explain mass phenomena through energy mechanisms.

The mismatch is particularly acute for the ISSN’s audience. Sports nutrition practitioners work in grams. They recommend protein in grams per kilogram. They track body composition in kilograms. They assess training loads in kilograms and repetitions. Every practical decision they make is a mass decision. The framework they are given is an energy framework.

The result is logical inconsistency. Not because the authors are careless, but because the framework forces it. When a derived quantity is treated as primary, contradictions are inevitable. When a law of energy is invoked to justify a claim about mass, the law is silent.

The documents are already mass-based. They recommend protein in grams per kilogram. They assess outcomes in kilograms. They present findings that are more consistent with MBM than with EBM. They have not yet named themselves as mass-based.

6. Conclusion

The ISSN has published two documents on diet and body weight regulation. Both are thorough, evidence-based, and practically useful for their intended audience. Both contain the same category error at their foundation.

The position stand calls the caloric deficit axiomatic. It is not an axiom. It is a derived quantity.

The review invokes the First Law of Thermodynamics. The First Law concerns energy. It says nothing about mass.

Both documents present mass phenomena in energy language, and both produce logical contradictions as a result. The contradictions are not incidental. They are structural.

A full inventory of every contradiction in both documents would require several thousand words. It is not necessary. The error is structural, and the pattern is clear.

Both documents are already mass-based. They have not yet named themselves as one.