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Your Body is Not a Calculator: The 7 Flaws of Calories In, Calories Out

Image of a Calorie Counter

The first and most common weight loss advice is always “calories in, calories out. You have to expend more calories than you take in.” It is stated as if it is a universal truth humans have known for millennia, when in fact it is far from universal and can be actively harmful.

Trust me, I wish weight loss was a simple calculation problem. I wish our bodies acted like calculators. I would love to have such a simple solution to health and body size. It would have saved me a lot of time, money, and stigmatizing experiences.

But our bodies run on biology, not math. I know calories in, calories out (CICO) sounds intuitive, but it is a drastic oversimplification that relies on a bunch of false assumptions.

1. All Calories Are Not Created Equal

A bunch of foods in a heart shape

Intuitively we all know this to be true. All calories are not the same. 500 calories of chicken do different things in our body than 500 calories of broccoli. We probably wouldn’t even eat 500 calories of broccoli in one sitting (like 16 cups of broccoli) because we’d start to feel very full from all the fiber and water. Whereas 500 calories of chicken (about 2 cups), most of us could eat in one sitting. Why? Because they are composed of different things which affect our bodies in a variety of ways. 

2. Calorie Counts are Inaccurate

nutrition label crossed out

A calorie (or kilocalorie) is the way we measure the available energy in all foods. It is the amount of energy required to heat one kilogram of water by one degree Celsius. They literally burn the food and see how much energy it gives off. Now, when contemplating the amount of calories in a package of food, companies make a rough estimate. There is no way to efficiently know the exact calorie amount of your specific food, packaged or not. Most labeling in the US has been proven to be inaccurate. And yet, the calories in, calories out method causes us to meticulously count what we are eating, and often feel guilty for “going over” when the whole this is just an estimate anyway! 

3. Our Genetics Play a HUGE Role

picture of DNA

Even in the most controlled studies, caloric control doesn’t provide the same results for everyone. The CICO method assumes that body size is solely a matter of personal control, but how our bodies use calories depends on many things like metabolism, muscle mass, gut health, and many other genetic factors. We can eat the same number of calories as someone else and have very different outcomes. Again, we all know this intuitively. We all know someone who eats a lot and is very thin. We attribute this to their “fast metabolism” and yet when it comes to fat people it is only about what they eat. A study in the New England Journal of Medicine found that the heritability of “obesity” is estimated at 40% to 70% (for reference height is 60% to 80% of genetic influence). So, how someone’s body reacts to CICO is not universal.

4. Hormones Matter

hormone molecule with hearts instead of O

The CICO method overlooks the crucial role hormones play in how bodies use calories. Hormones like Insulin, ghrelin, and leptin tell our bodies how to regulate hunger, metabolism, fat storage, and many more functions. These hormonal systems can be dysregulated by medications or medical conditions, but you can also inherit the way these hormones operate from ancestors.

5. Medical Conditions and Medications

medical bag and items

Medical conditions and/or medications can cause fluctuations in your body size and weight for a variety or reasons. Medications can change appetite, fluid retention, insulin levels, and many other biological factors that can cause fluctuations. Thyroid issues, Cushing's Syndrome, Crones Disease, Polycystic Ovary Syndrome (PCOS), and many other conditions can cause weight change. Mental health conditions can also influence weight fluctuations due to a variety of factors. Not to mention, some conditions and medications affect energy levels and can make it difficult to predictable engage in the activities of daily living let alone, movement or cooking.

6. Promotes Disordered Eating

a woman struggling

Calories counting literally trains us to have a disordered relationship with food. It can lead to an unhealthy obsession, restrictive eating patterns, and fosters a negative relationship with food. The rhetoric around calories creates the moralization of food. Food is “good” or “bad” and what foods we eat then make us “good” or “bad.”

7. Inequalities in Society

one person with lots of money and one

Calories in, calories out completely ignores the unequal access people have to income, diverse or fresh food, healthcare, a safe place to move, education, stable income, healthy neighborhoods to live in, and safe work environments. All of this is the complex web that impacts our health. The most offensive crime of CICO is that it reinforces the idea of “individual responsibility” when it comes to health and body size, blaming individuals for societal failings or things beyond their control. 

While the concept of "calories in, calories out" feels like the right answer, it oversimplifies the complex factors involved in body size and health. Intuitive eating, gentle nutrition, weight neutrality, and other anti-diet approaches are sustainable because we know many factors influence your health and body size. We are individuals with different needs and priorities and each of us deserves to work with a professional who will support us as we support our bodies, health, and well-being. 

*Please know, that if you count calories and it works for you, great! I am not here to take that away. I believe you can do what you want with your body, but I also believe in informed consent and I'd like everyone to know that body size and health is more nuanced. Even if counting calories worked for you or your friend it might not work for everyone, so please don't spread misinformation.


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