While the data on niche diets for weight loss is mixed, there is one foundational principle that seems to be constant in most studies. That is that caloric deficit is the most significant factor in catalyzing weight loss through diet. The problem with this is that it doesn’t tell the whole story and does not mean that all calories are equal when they enter the human body. While it is true that through the lens of thermodynamics one calorie has the same amount of energy regardless of its composition, a calorie has a much more nuanced path in the human body. There are three principles we will talk about out in this article- 1.) the thermic effect of food, 2.) fiber, and 3.) calories that produce harmful byproducts when broken down by the human body which we’ll refer to as bad calories.
The Thermic Effect of Food
Once the calories enter your body, they are broken down and processed into compounds that are then carried to various parts of the body for use. This process takes energy, and depending on the type of calorie- protein, carbs etc.- the amount of energy it takes to process will vary. The energy used to process the various calories is known as the thermic effect of food (TEF). Protein tends to have the highest TEF while carbohydrates and fats have a lower TEF. Because of this factor we can reasonably conclude that the type of calorie matters. For example, if you ate 100 calories of white rice and 100 calories of ground beef, the net energy consumption by your body may differ due to the TEF of each food. This is not to say that TEF should be the sole factor in deciding what to eat for weight optimization, but it should certainly be a consideration.
Dietary Fiber
While it is well known that dietary fiber has a plethora of health benefits. We will focus on it through the lens of energy absorption once it enters the body. Dietary fiber is most commonly found naturally in fruits, vegetables, and grains. It is classified into two subsets- soluble and insoluble- with most natural sources containing both. So why does it matter when talking about energy absorption? Dietary fiber is resistant to digestion in the small intestine and thus passes through to the large intestine where it ferments and is consumed by the micro flora living inside you. Because it is more resistant to digestion it has been shown to decrease metabolizable energy [1]. It also produces glucagon like peptide (GLP-1) which is a key hormone in inducing satiety. So again, if we compared 100 calories of white rice with 100 calories of spinach, the total energy absorption would be lower with spinach and feelings of satiety would be lower with the rice.
Bad Calories
All calories produce a certain amount of waste or compounds that are not utilized for energy when they or processed. But because not all calories are the same, different calories produce different byproducts which have varying effects on the body. Alcohol for example produces a compound known as acetaldehyde which promotes cancer development [2]. Another example, high fructose corn syrup produces a by product called uric acid which leads to chronic inflammation. Furthermore, because the liver has a limited capacity to process fructose, excessive amounts can lead to fat storage on the outside of the liver. The last example of “bad calories” is trans fats. Trans fats are unable to be fully broken down in the body and have been shown to contribute to inflammation and heart disease [4]. The point here is that bad calories ingested lead to compounds that loom inside the body and cause damage whereas other calories do not.
Conclusion
In summary, types of calories matter in the context of human energy absorption. If you focus solely on caloric deficit to meet your weight loss goals, you will likely lose weight but, you may create more problems for yourself along the way. That is why it is important to take a broader and more wholistic approach to formulating a sustainable and healthy diet. Consider these factors when looking for or creating dietary guidelines for optimized health, TEF is higher in some foods, fiber both limits energy absorption and induces satiety, and “bad calories” may stay in your body long after they are consumed.
References
[1]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257631/
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6527027/
