Counting Calories: The Basics

A calorie serves as a unit of measurement in chemistry. Specifically, a food calorie indicates the amount of heat energy required to increase the temperature of 1 kilogram of water by 1 degree Celsius. These kilocalories (1,000 calories), commonly referred to as "Calories" with a capital C, are what you see on food labels and calorie-tracking apps.

Historically, determining the caloric value of food was a laborious task until scientists developed a formula to estimate the energy content provided by macronutrients (the Atwater equation):

• 4 calories per gram of protein
• 4 calories per gram of carbohydrate
• 9 calories per gram of fat
• 7 calories per gram of alcohol

These values remain the standard for most industry organizations and the USDA when estimating the caloric content of foods. Food manufacturers, app developers, and healthcare professionals rely on these figures to create food labels and establish caloric goals for weight management.

However, recent scientific findings indicate that the actual caloric absorption from food can vary based on its preparation and the individual's biology.

The Discrepancy Between Ingested and Absorbed Calories

Almonds exemplify this issue. The Atwater equation posits that a person absorbs 170 calories from a serving (¼ cup) of almonds. Yet, research suggests that the way food is consumed can alter the actual calories absorbed.

A series of studies starting in 2013 demonstrated this phenomenon: when participants consumed almonds with a label indicating 170 calories per serving, their bodies absorbed an average of:

• 123 calories from whole, unroasted almonds
• 138 calories from whole, roasted almonds
• 141 calories from chopped, roasted almonds
• 170 calories from almond butter

Almonds are not unique in this regard; small variations in caloric absorption can lead to discrepancies of hundreds of calories over time between what individuals believe they're consuming and what they're actually absorbing.

So, how are these facts conveyed to consumers? Typically, they are not.

Consider the calorie counts listed on labels and apps for different almond preparations. Most still reflect 170 calories per serving. Updating this information across countless food products whenever new findings arise would be prohibitively expensive for companies. Even if updates were made, they would still lack precision for each individual user, primarily due to food preparation methods.

The Role of Food Preparation

Take, for instance, a whole, unroasted almond. This small nut is packed with nutrition, comprising fat, protein, fiber, polyphenols, vitamins, and minerals, all held together by a complex structure known as the "food matrix." When consumed whole, the body cannot fully digest and absorb all the nutrients available, leaving some behind as undigested fibers or fats.

However, when almonds are chopped or transformed into almond butter, the food matrix alters, allowing the body to absorb more calories and nutrients from the same quantity of food. This is why dietitians often suggest incorporating smoothies for those who are malnourished or looking to gain weight; the blended ingredients provide more calories and nutrients than when consumed whole.

This principle has also led some clients to inadvertently gain weight when adding smoothies to their diets without realizing that the caloric absorption could be higher than from whole foods.

At first glance, one might think that adjusting calorie estimates based on food processing would yield accurate counts. Unfortunately, this is not the case.

The Impact of Gut Microbiome

The bacteria residing in our intestines, known as the gut microbiome, play a significant role in how we metabolize food. Despite what supplement companies claim, we are still years away from fully understanding how to support a healthy gut microbiome, or even defining what a "healthy" microbiome looks like.

What is clear, however, is that gut bacteria require nourishment, and their diet is influenced by what an individual consumes. Some bacteria are more adept at metabolizing food energy, while others produce compounds that can enhance nutritional absorption.

Individuals with a higher concentration of efficient metabolizing bacteria may absorb more nutrients, leading to greater caloric storage compared to someone who has eaten the same meal but has a different microbiome composition.

These small variances can accumulate to affect daily caloric intake, ultimately influencing weight management and nutrient absorption.

The Influence of Health Conditions

During my own journey, I gained 15 pounds in three months while pursuing a PhD in Nutrition Science. It soon became apparent that my struggle stemmed from hypothyroidism, a condition that can reduce daily caloric expenditure. Other chronic health conditions, such as thyroid disorders, bowel diseases, and lung diseases, can alter the rate at which the body utilizes calories and nutrients.

While we have less clarity on whether these chronic diseases affect caloric absorption, it's known that conditions like diabetes, Crohn’s disease, and heart failure can impact the gut microbiome, potentially increasing the bacteria that facilitate greater energy absorption.

The relationship between chronic diseases and caloric absorption is complex and not fully understood. However, it is evident that an individual's medical history can significantly influence the accuracy of calorie counting apps.

Taking Calorie Counts with a Grain of Salt

Calorie counting applications can still serve as useful tools for guiding overall dietary habits. I often recommend these apps to clients to help them gauge feelings of fullness or hunger across various caloric ranges. However, I advise caution for those with a history of disordered eating or who find that tracking calories induces anxiety.

It's important to remember that calorie counts are not infallible. Do not allow this to become a source of stress. Striving for a precise caloric intake daily is not a sustainable or joyful way to live unless dictated by specific medical needs. The body's caloric requirements fluctuate daily. Therefore, any health strategy should ultimately enhance your enjoyment of life and food.