There seems to be a huge concern about calories, how many we ingest and how many we (should) burn. But the ultimate questions about calories are:
What do they really measure? Should we count them and how?
What are calories?
Calories measure the energy contained in food and so, they enable us to keep track of the body’s energy budget. This budget is balanced and an adequate energy supply is achieved when we put in about as many calories as we lose. If we consistently supply our body with excess calories, they will be stored in the form of fat, and we will gain weight. On the contrary, if we burn off more energy than we replenish, we will lose weight and might feel a decrease of energy or even fatigue. To that extent, calories can be an interesting tool to make sure that we provide our body with the energy it needs.
What do we use calories for?
Everything we eat stores a certain amount of calories (hence energy) in its chemical bonds. That energy is released during digestion and re-stored in a way that can be utilized whenever the body requires energy. 10% of this energy is used for digestion, 20% fuels physical activity and 70% supports basic functions of our organs and tissues. This last energetic need is called our basal metabolic rate, and refers to the calories needed at rest for survival. But the 3 components together determine how many calories each person should aim to consume each day.
Why should we count calories?
However, counting calories is not as simple and systematic as it sounds! First, a person’s caloric needs depend upon their weight, physical activity and muscle mass. Someone biking the Tour de France would for example burn around 9000 Kcal per day! Likewise, pregnant women have a higher need for energy that increases as the fetus develops, and as they prepare for delivery and lactation. Elderly on another hand tend to have a slower metabolism and thus need less calories. Besides, how much energy the food contains does not equal how much energy we get from it. Fiber-rich ingredients like celery actually require more energy to digest than the energy they provide. Finally, each individual extracts different amounts of energy from the same foods, according to their digestive health, which includes their enzyme production, gut bacteria population, and even intestine length. At this point of our reflection, it is important to understand that calories are a general indicator. As we have mentioned above, they first must be considered at the individual’s level to make sure they match every person’s right energy requirements. In short, calories are a good starting point or framework to reconnect with our bodies’ primary energy needs, as inadequate calorie intake can result in both over and under-eating.
The prevalence of obesity in modern societies raises growing awareness about profound changes in our environment and notably our diet. Agriculture and animal husbandry developed approximately 10000 years ago, introducing crucial alterations of our dietary habits. Current scientific research identifies obesity as a proof of inadaptation, or adaptation failure to these changes. They are thought to have happened too recently on an evolutionary time scale for the human genome to adjust. From an ancestral perspective, the physiological storage of fat is temporary, seasonal and adaptive and has helped humans survive periods of scarcity and famine. To that extent, it is designed to be an advantageous physiological mechanism. Nowadays though, we live in a food-abundant environment where that storage mechanism no longer serves us well, and in which excessive stored energy is often useless, thus superfluous and detrimental.
On the other hand, undereating is too often overlooked. Dietary restrictions, daily life pace and stress, intense physical activity and special phases of life sometimes force our body to cope with calorie deficit. Under-eating may lead to metabolic disorders and changes in our homeostatic balance, affecting our hormones and overall physiology. Chronically calorie-deprived people present with increased stress hormone levels, which can lead to decreased insulin sensitivity and prevent us from losing body weight. So contrary to common belief, calorie deficit does not equal weight loss, which might muddy the waters and prevent people from accurately addressing their dietary habits.
Are calories enough to determine a healthy diet?
Calories should never become an absolute outcome. They are a partial and incomplete tool and can not reflect a healthy diet on their own. When misunderstood and misused, counting calories can also lead to a progressive urge of control and result in eating disorders with devastating effects on the body and mind.
Another limitation to the meaning of calories is that they are no indicator of the nutritional value of foods. A correct calorie intake thereby might hide a lack of proper nutrients. We get calories from 3 different types of macronutrients found in food: 1 gram of carbohydrates or proteins provides us with 4 Kcal, whereas 1 gram of fat contains 9 Kcal. Junk food is typically very high in carbs and fat, which is why it is often referred to as hyper caloric. But beyond the macronutrients we obtain the calories from, we must also be cautious with their micronutrient content and their source. Eating organic grass-fed meat, seasonal fruits and vegetables, wild-caught fish and free-range eggs will provide the body with high quality nutrients together with the calories they provide. On the other hand, Eating fast-food elaborated from grain-fed and hormonally boosted meat, cooked in highly refined and industrial oils, drinking canned juices or sodas, might fulfill your energy requirement for a while, but will not feed you with the complex and delicate mix of nutrients you require to thrive and will actually starve your body of truly nutritive food. This comparison explains how overweight and malnourishment often go hand in hand.
