Technically speaking, a calorie is defined as the energy needed to raise the temperature of one gram of water by one degree Celsius. More commonly, calories are used as a way to define whether or not something is good for you. A food that is low in calories is considered healthy, and a food that is high in calories is considered unhealthy. But what if the calorie is not a consistent measurement?

This is what 200 calories of various foods looks like

For many years, doctors have been attempting to resolve the obesity epidemic by prescribing the simple advice that a person needs to balance the calories they take in to the calories they expend during the course of a day. This appears to be reasonable advice; it’s a simple matter of balancing input and output. The accuracy of this advice comes into question when numerous studies begin showing that not all calories are the same.

In a study published by the American Journal of Clinical Nutrition, weight loss was compared between adults that ate diets high in protein/low in carbohydrates and adults that ate diets low in fat. The article states, “diets high in protein/low in carbohydrates produced an 2.5-kg greater weight loss after 12 weeks of treatment… further research on differences in the composition of weight loss is needed to explain the observed increase in weight loss”. Although unexplainable, these conclusions are significant. This demonstrates that not all calories are equal, and the human body responds to the differences in calorie quality.

The movie Fed Up also discusses this topic. In this video clip titled Why a Calorie Is Not a Calorie, the example of almonds vs. soda is used to prove this concept. The fiber in the almonds slows down the absorption of the food and prevents a spike in blood sugar. Since the soda doesn’t have any fiber, the sugar goes straight through the body, spiking the blood sugar, and leaves the body with no choice but to turn it into fat. Even though the almonds and soda had the same caloric content, the body reacted to them very differently.

A PBS article explains that even though there is no exact answer to this question, nutritionists have been able to formulate some ideas as to why the body responds differently to calories from different foods. The article states, “we burn more calories while metabolizing protein than while metabolizing the other two so-called macronutrients… our bodies might use calories from diets higher in protein less efficiently, resulting in less fat storage or greater weight loss”. If this was the case, it would explain why the American Journal article observed the conclusions it did.

Dr. Mark Hyman, one of the doctors featured in Fed Up, wrote an excellent article explaining this exact concept. His example of sixth graders clarifies the concept when he states, “show them a picture of 1,000 calories of broccoli and 1,000 calories of soda, ask them if they have the same effect on our bodies, their unanimous response will be ‘NO’”. This relates back to the previous topic of how almonds and soda are digested differently. Although the number of calories is the same, the presence of other nutrients determines how many of those calories are absorbed into the body.

This question also relates to a topic discussed in class: whether or not sugary drink consumption is linked to obesity. Even though there are not enough studies on sugary drinks, there is evidence pointing towards the conclusion that yes, sugary drinks are connected to obesity. This question of differences in calories is connected because sugary drinks would be considered a bad source of calories since there’s nothing to slow down the absorption of sugar into the body.

Although many more studies are needed on this topic to be able to draw concrete conclusions, there is currently a growing amount of evidence supporting the thought that a calorie does not equal a calorie. This information could be very important in making a break through in solving the U.S. obesity epidemic and better educating children in the future.