Not all Calories are Equal


In the recent article on The Conversation, Terezie Tolar-Peterson, an associate Professor of Food Science, Nutrition & Health Promotion at Mississippi State University, discusses that not all calories are equal when it comes to health and the body’s energy balance, as well as their impact on health and weight management.

For example, some studies have reported that diets that are high-protein, low-carbohydrate or a combination of the two do yield greater weight loss than diets with other levels of fat, protein and carbs.

If every calorie in food were the same, you wouldn’t expect to see weight-loss differences among people who eat the same number of calories that are doled out in different types of food.

– Terezie Tolar-Peterson on The Conversation

The article focuses on several key aspects:

  • Energy actually available to your body. Prof Tolar-Person explains that in the late 1800s, chemist W.O. Atwater and his colleagues developed a method to determine the calorie content of foods by burning samples and measuring the energy released. However, not all energy in food is usable by the body; metabolizable energy is the energy left after deducting what passes through feces and urine. Atwater established percentages of metabolizable energy for proteins, carbohydrates, and fats. This system, still used by the U.S. Department of Agriculture, estimates the calorie content of foods based on these calculations for each macronutrient.
  • How much energy you use. Prof Tolar-Person explains that diet affects the body’s energy expenditure, including basic functions and physical activity, known as metabolism. This is influenced by the thermic effect of food, where low-carb diets lead to higher energy expenditure compared to low-fat diets. Similarly, high-fat diets reduce total energy expenditure compared to high-carb ones. Increasing protein intake to 30%-35% of the diet can boost energy expenditure. Generally, diets rich in carbohydrates, fat, or both increase energy expenditure by 4%-8%, while high-protein meals raise it by 11%-14% due to the harder breakdown of protein. These subtle effects may contribute to the obesity epidemic by promoting slight weight gain.
  • Quality of the calories you eat. Prof Tolar-Person highlights the significance of a food’s glycemic index and load in affecting blood glucose levels and subsequent insulin release, influencing energy metabolism and fat storage. Foods high on the glycemic index/load, like white rice and sweets, activate brain reward centers, leading to pleasurable effects. Additionally, fiber-rich foods, such as fruits and whole grains, offer fewer metabolizable calories and promote satiety. Conversely, empty calories from sugary snacks lack nutritional value and can contribute to weight gain, contrasting with nutrient-dense options like vegetables and nuts, which are associated with weight maintenance or loss.
  • More to health than calories and weight. Prof Tolar-Person stresses the importance of calorie balance for weight loss but emphasizes that weight alone doesn’t guarantee health. While high-protein diets may aid short-term weight loss, longevity is associated with plant-based diets low in animal protein and moderate in healthy fats. She clarifies misconceptions about carbohydrates, advocating for reducing simple carbs while embracing nutritious options like fruits and vegetables. Encouraging a plant-based diet for disease prevention, she underscores the decline in nutritional quality in the modern Western diet and urges prioritizing food quality over calorie count for better health.

The article demonstrates how important it’s to consider different aspects of calories intake, such as diet composition, metabolizable energy, and food quality, in order to promote optimal health outcomes.

Acknowledgements: ChatGPT was used to summarize some content and prepare its first draft.