Acquiring food used to be hard work. Whether it was walking to a water source to obtain water, gathering fruit, or hunting a large animal and dragging it to camp, getting resources required a lot of effort. Therefore, our bodies are imprinted with the expectation that energy expenditure (burning calories) is related to consuming them – as opposed to a sea sponge, for example, that is designed to sit in one spot all day and eat.
What did acquiring food used to look like? Here is a quote from Professor Loren Cordain:
• “Our Paleolithic ancestors exerted themselves daily to secure their food, water, and protection.
• Our remote ancestors participated in various physical activities daily. They walked and ran 5 to 10 miles daily as they foraged and hunted for their food sources.
• They also lifted, carried, climbed, stretched, leaped, and did whatever else was necessary to secure their sustenance and protection.
• Days of heavy exertion were followed by recovery days. In modern terms, these people cross-trained with aerobic, resistance, and flexibility exercises.
• Even in times of caloric excess, hunter-gatherers avoided weight gain in part because they were extremely physically active.
• Although modern technology has made physical exertion optional, it is still important to exercise as though our survival depended on it, and in a different way it still does.
• A sedentary existence predisposes us to obesity, hypertension, the metabolic syndrome, diabetes, and most types of cardiovascular disease, whereas regular exercise decreases the risks of developing all these diseases.
• We are genetically adapted to live an extremely physically active lifestyle.“
-Cordain, Loren, O’Keefe, James H. Cardiovascular Disease Resulting From a Diet and Lifestyle at Odds With Our Paleolithic Genome: How to Become a 21st-Century Hunter-Gatherer. Mayo Clin Proc. 2004;79:101-108
Today there is a much different situation when it comes to acquiring food. Today, food is much more plentiful, energy dense, and easier to obtain. Check out this history of the energy involved in getting food today. Think about it: how many opportunities are there in your town to get your hands on a meal without ever leaving your car?
What is a Calorie Exactly?
A calorie is a unit of energy. Technically, it is the amount of energy required to raise the temperature of one kilogram of water by one degree Celsius. A typical human diet can consist of anywhere from under 2,000 to over 3,000 calories of energy consumed in food per day.
Of course, your body has specific fuel sources it can use for energy. Your body is designed to metabolize, or burn, three categories: fat, carbohydrate and protein. Fat is the most energy-dense energy source. Fat contains 9 calories for every gram of fat. Protein and carbohydrate both contain 4 calories per gram.
When you eat food, it contains a certain amount of calories. However, there are other substances in food that do not contain calories. Water and fiber are two of the most important of these. Other nutrients in food that are present in smaller amounts are vitamins, minerals and phytochemicals.
Some foods are more calorie dense than others. Meaning that for the same volume of food, the calorie content can vary widely. A hundred calories can come in the form of a large head of lettuce, or in the form of a small candy bar. Good fuel sources are typically lower in calorie density than processed foods. Good fuel sources typically have a high fiber and water content. Processed foods tend to be very low in fiber and water, and also tend to have lots of toxic additives as well.
The result of these changes in energy acquisition and energy consumption has led to an energy imbalance. In other words, we are too often consuming more energy, or calories, than we are expending. The occurrence of this energy imbalance problem is at the root of the world-wide obesity epidemic.