Do We Have Obesity Science Right?
If I were to tell you that obesity science has misinterpreted many of its findings due to incorrect modelling and assumptions, you would likely be dismissive. How could that be? Science and studies are so advanced that we could not be wrong. I think it is normal to dismiss such a contrary view, yet there are past examples that demonstrate it happens. We are not infallible!
We Don’t Always Get it Right
One example is stomach ulcers. The assumption that microbes could not survive in the stomach’s acidic environment resulted in the misinterpretation of research findings that directed treatment with antacids and surgery that never resolved a chronic condition. In fact, stomach ulcers are now cured with a course of common antibiotics because it was discovered that the assumption was wrong.
In nutrition, the assumption that trans-fats were not unhealthy, led to decades of recommendations to consume products made from very harmful partially hydrogenated vegetable oils. The FDA only removed their GRAS (Generally Recognized as Safe) status in 2015 when the danger was demonstrated about 1990! In hindsight, it seems obvious, and we can laugh at our past ignorance, but when you are in that moment, the dissenting voices are usually called ‘crackpots’.
I am not suggesting that crackpots are always right, or that these examples prove that we have the same situation in obesity science. I am saying that sometimes we need to go back and challenge fundamental assumptions, especially when our attempts to apply scientific knowledge in practice continue to fail.
Moving Forward Means Looking Back
For obesity science, medicine, and treatments to move forward, we should highlight inconsistencies and challenge fundamental assumptions that have not been tested or perhaps are not even recognized as assumptions. I will make the case for this, and I hope that you will approach it with an open and curious mind, like that of a juror.
What is the cost of doing this? It requires taking the time to reflect on the problem from first principles. However, if we do find that there are flawed assumptions, the payoff could be a better understanding of one of the biggest health problems of our time.
Let’s start from a common point with some facts that almost nobody should disagree with:
- While some individuals have success in losing weight, even fewer can maintain long-term weight loss.
- What we are currently doing and have done to address obesity on a societal level has not worked.
- The indisputable cause of obesity is the accumulation of excess fat mass.
Instead of immediately jumping to hypothetical reasons to explain why facts 1 and 2 happen, the purpose here is to prompt us to explore our assumptions. Fact 3 provides us with an indisputable starting point, so what are the assumptions?
- Most researchers accept that obesity is caused by positive energy imbalance using the Energy Balance Model (EBM). In other words: “When we consume more calories than our body requires, our body stores the excess energy as fat, leading to weight gain and eventually obesity.”
Exploring the Gap
I propose that we explore the gap between statements 3 and 4. If statements 3 and 4 are both true, then we should be able to connect the two using solid physics, because these statements are SOLELY within the realm of physics.
Starting with statement 3, what are the physics-based ground rules? Firstly, we are talking about the accumulation of (fat) mass resulting from net usage. The only relevant physics is the law of conservation of mass . We get heavier when we store fuel mass that is not used to make energy. The mass from fuel we use to create energy, in the majority, is breathed out as CO2 .
Unfortunately, as the survey results show below, the generally accepted view of many health professionals (perhaps facilitated by the EBM) conflates mass and energy. Weight lost is not converted into energy to disappear as energy/heat. If it did, we would all be walking nuclear bombs! In fact, it is mostly breathed out.
The Real Physics of Weight Loss
Statement 3 is only about mass and is covered by the law of conservation of mass so how do we connect mass and energy as required by statement 4? The fundamental relationship was determined by Einstein’s equation: E=mc2 .
Cutting to the chase, when we metabolize fuel for energy, the near-infinitesimal mass of the chemical bonds of fuel is converted into energy (4.56 x 10-12g per Calorie). The bulk of the weight is exhaled as waste CO2 (~85%), and the remainder (~15%) is excreted through other means. Excess fuel that we don’t use to produce energy is stored (mostly as fat), and this surplus fuel adds to our weight. You can think of it like an empty diesel tanker where the engine’s diesel tank, if overfilled, overflows into the larger storage tank, making the tanker slightly heavier. Unless the fuel from the large tank all flows back to the engine tank to be burned in the engine, over time the weight of fuel in the storage tank could become significant.
Is Flour the same as Bread?
Somewhat pedantically (but important from a system modelling perspective) calories are the output from our metabolic processes and not an input. To draw an analogy, if you bought one kilogram of flour, you could say, “I just bought two loaves of bread.”. Intuitively, we know this isn’t correct because the breadmaking process requires several other ingredients (yeast, water, and salt for taste) and processes (fermentation, kneading, proving, and baking) to turn flour into bread. Flour is an input, and bread is the output of the breadmaking process- just as food is the input and calories are the output of our metabolic processes. In fact, the flour may not become bread at all; it can fail to rise or have a different process output, such as pasta. By saying you have bought bread when you have bought flour, you have assumed both the intent and success of breadmaking.
Analogously, when if predetermine fuel is calories, we assume the intent and success of energy production. While we recognise the absurdity of saying that flour is bread, it is generally accepted that fats, carbohydrates, protein, and alcohol are calories. The packets that wrap our food even tell us so! If it were not for our inertia to accept observational scientific agreement, I think we would discard this as nonsense.
Convenience over Accuracy?
While it is convenient to use the term “calories consumed” to refer to the energy obtained from food, it is important to acknowledge that the human body is not a perfect “calorie counting” machine. The way our bodies process and utilize energy from different types of foods can vary, and factors such as nutrient composition, food processing, and individual differences in metabolism can all affect the way our bodies handle energy.
Additionally, other factors beyond energy balance, such as the quality and composition of the diet, overall dietary patterns, and lifestyle behaviours, can also play a role in the development of obesity. For example, the type and quality of macronutrients consumed (e.g., carbohydrates, fats, proteins), the presence of added sugars or processed foods in the diet, meal timing, portion sizes, and eating behaviours can all impact weight regulation and the development of obesity.
Therefore, it is important to acknowledge that the energy balance model is an oversimplified representation of the complex interplay of factors that contribute to obesity, and it may not capture the full complexity of the human body’s response to energy intake and expenditure. While further research is needed to better understand the multifactorial nature of obesity and develop more comprehensive models that consider the complexities of human physiology, metabolism, and behaviour, it’s also possible that the clues are already in the scientific literature, but they are unlikely to be found in studies that are based on a fundamental oversimplification of (and I would go further to say wrong) system modelling.
- The misunderstanding of stomach ulcers and trans-fats shows that widely held views in medicine and nutrition can be incorrect.
- The widely accepted view is that obesity is caused by an energy surplus as calories consumed are greater than calories expended.
- It is a valid exercise to personally challenge fundamental that model assumption and may be necessary for obesity science, medicine, and treatment to solve one of the biggest health problems of our time.
- Clearly, it is the accumulation of excess fuel as fat in the body leads to weight gain and obesity.
- The physics ground rules for understanding obesity are the law of conservation of mass and the relationship between mass and energy (E=mc2).
- From conservation of mass, most of the weight lost is through breathing out ‘waste’ CO2, while the mass of the chemical bonds of fuel converted into energy is negligible.
- Calories are the output of metabolic processes, not an input, and should be seen as the output of the food-to-energy conversion process.
- Summary points 4 to 7 provide a solid starting point to examine the energy balance model of obesity.
The EBM Clearly Has Some Validity
I acknowledge that studies show that when individuals consume more potential calories than they expend, they gain weight, and when they consume fewer potential calories than they expend, they lose weight, so it is reasonable to conclude that an energy imbalance has a role in the development of obesity, and while the energy balance model may have invalid assumptions, it has been useful as a principle to guide interventions for many individuals who struggle with obesity.
Additionally, approaches that focus on reducing caloric intake, increasing physical activity, and improving overall health behaviours clearly have positive effect. The energy balance model has been well-supported by observational research and is widely accepted in the scientific community but none of that makes a model correct. While the EBM appears to be based on the principle of conservation of energy, which is a fundamental law of physics of CLOSED SYSTEMS, more fundamental are the laws of conservation of mass and energy mass conversion which form a physics base that do not conflate energy with mass.
Where to From Here?
This is the end of part one and I think I have achieved the aim of demonstrating that there is a case to be answered. In further parts, I will move on to look further into the implications of these and other surfaced assumptions and incorrect systems modelling to propose different ways to consider the problem that are consistent with existing evidence and importantly, use good system modelling.
 The Conservation of Mass. (n.d.). Scitable by Nature Education. Retrieved from https://www.nature.com/scitable/knowledge/library/the-conservation-of-mass-17395478/
 Ruben Meerman and Andrew J. Brown. (2014). When we lose weight, where does it go? The Conversation. Retrieved from https://theconversation.com/when-we-lose-weight-where-does-it-go-91594
 Mass-energy equivalence. (n.d.). In Wikipedia. Retrieved from https://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence