Calories: We study them listed through our fitness trackers, noting how many we burned. We consider them on nutrition facts panels and some restaurant menus to monitor how many we take in. We use this little unit as a currency to control our energy balance in an effort to achieve and maintain our ideal body weight. This currency is so valuable that we want to believe that it is infallible. But what if it isn’t? It turns out that there are unknown factors that may be affecting energy balance and metabolism.
The first factor influencing calorie absorption and therefore your metabolism is your gut microbiome. Our gut is rich in bacteria that need to be kept in a good and beneficial balance. There is science that suggests good bacteria (probiotics) may benefit our bodies in a variety of ways, including the way we absorb calories and therefore our metabolism. Researchers have found, in fact, that when our gut bacteria are imbalanced we are at greater risk of becoming overweight. Scientists are looking toward a time when we may have tailored probiotics to assist individuals in achieving a better bacteria balance.
Researchers have also found that the way we digest certain foods affects how many calories we absorb from that food and thereby ultimately our metabolism. Specifically, it seems that nuts, which are uniquely rich in both fiber and healthful fat, and therefore digest slowly, may not be absorbed the way we thought. With fibrous foods like nuts, digestion has to begin with good chewing, and in our rush to eat most of us don’t chew enough. Ultimately, we don’t break down nuts entirely and therefore don’t actually take in as many calories as are listed on the nutrition facts panel.
Lastly, diet composition may influence calorie absorption and metabolism. Researchers have found that it isn’t always the number of calories we consume, but rather what those calories are composed of in terms of fat, protein, and carbohydrate. So it may not just be how much food you eat, but rather what you eat, as well as the timing of your meals that impacts your metabolism.
It is natural to ask if calories still matter. The answer (at least for now) is yes. While it may not be the perfect currency we wish it was, it is the only currency we have. That said, the science around factors that influence calorie absorption will continue to evolve. Keep an eye on this interesting space and stay tuned for more information and guidance to come.
Allison Stowell is a Consulting Dietitian at Guiding Stars.