If you consistently ate processed meals of 2000 calories comprising burgers, fries and soda pop or whole food meals of 2000 calories comprising brown rice, beans, fruits and vegetables (all other variables remaining the same – in terms of physical activity, amount of sleep, etc.), would you gain (or lose, depending on your daily caloric requirement) the same amount of weight from each? Another way of asking this question is – Is a calorie a calorie? Or, are all calories the same?
In order to answer that question, I’m going to ask another question: what are the different ways in which we use the calories that we eat?
Basal Metabolic Rate (BMR), or the term we refer to as the minimum amount of energy spent to keep us alive when the body is at rest, and physical activity are the two main uses for our calories. Can you think of anything else? Do you need calories to digest and absorb food?
Energy expenditure includes –
- Basal Metabolic Rate (BMR, the term for energy spent to keep us alive at rest) which includes important functions like beating of the heart and breathing
- Physical activity
- Digesting, absorbing, transporting, metabolising, storing and distributing the nutrients in food, collectively known as the Thermic Effect of Food (TEF), Specific Dynamic Action (SDA) or Dietary Induced Thermogenesis (DIT), accounting for roughly 10% of calories spent daily.
Energy intake refers to the calories from our meals, but it can be more complicated when we factor in the energy used from digesting our food to arrive at the ‘net’ calories consumed. Think celery. While celery itself has zero calories, when our body tries to digest the celery, it uses energy to break down the tough walls and absorb the nutrition in the celery. The net energy input from eating a stick of celery is therefore negative.
It is in our best interest to eat the kinds of food that will require more effort for the body to digest and absorb, so that we end up with fewer calories.
The average person uses about 10% of daily energy expenditure in digestion and absorption but the percentage depends on the type of food eaten. Protein requires about 20-30% of its calories for digestion, carbs require 5-10% (depending on the complexity of the carb), and fats require 0-5% of the calories. 100 calories from protein, therefore, would require 20-30 calories for digestion and absorption, and the net calorie gain would be 70-80 calories. Likewise, the net calories from carbs would be in the range of 90-95, and from 95-100 from fats for the same 100 calories. Since the primary function of protein is building and repairing the body, protein is not an efficient source of energy and its conversion to energy involves a complex process and whatever is not converted to glucose is excreted through urine. Would you still say “a calorie is a calorie”? I don’t think so J.
Photo – http://getrefe.tumblr.com/
The level of processing of foods also determines the net calories gained. Processed foods are bad – not just because they are nutritionally bereft and have a myriad of synthetic and usually harmful chemicals that go into them, but also because they are more simply digested. This means that our body doesn’t need to work as hard on digestion, causing less energy loss and consequently more energy absorption, even with products having the same number of calories. There is more ‘net’ calorie assimilation with refined foods. Whole foods and the higher nutrient content in them – namely fibre, vitamins and protein, need more effort to be broken down and digested, resulting in a substantial amount of energy lost and fewer ‘net’ calories whereas processed foods are usually high in simple carbs and low in protein. Fewer calories per calorie, wouldn`t you agree?
Want to increase your energy expenditure? Eat more complex, whole foods so your body needs to work hard digesting and absorbing it and you get fewer calories from them in the bargain.
Here’s a research study to illustrate this fact: In a study funded by the Howard Hughes Medical Institute and Pomona College, seventeen subjects were given on two different days, two bread-and-cheese sandwiches that were the same in terms of caloric content (subjects could choose from 600 or 800 calorie portion sizes for each meal) but one was ″whole food″, comprising of multi-grain bread (containing whole sunflower seeds and whole-grain kernels) and cheddar cheese, while the other was ″processed food″, comprising of white bread and a processed cheese product. Each meal (and portion size) derived the same proportion of energy from both the bread and cheese (60% bread, 40% cheese). The whole food meal was 40% carb, 39% fat, and 20% protein; and the processed meal was 50% carb, 33% fat, and 15% protein. The whole food meal had about thrice the amount of dietary fiber than the processed meal.The researchers measured the extra energy over the BMR that each subject expended for six hours following the consumption of the meal. Without getting into the technicalities, let’s jump to the results. It was found that the subjects got 9.7% less net energy from the whole food meal than from the processed food meal as a result of DIT (TEF) in action. On a 2000 calorie diet, this translates to a net calorie intake of 1806, or a calorie loss of 194!. Of course, this value would vary greatly depending on the type of food and level of processing. The less processed the meal, the greater the energy loss, and vice versa. This calorie loss is without any kind of physical activity. So even if you do not exercise at all (which is not recommended, btw) you will still lose these calories by just eating whole food meals. But guess what, the energy loss from TEF can be increased if you exercise.
Other factors affecting TEF are exercise (studies have found that TEF is enhanced by aerobic endurance exercise and resistance exercise), the level of lean mass in men (a study found that men with more lean mass had significantly higher TEF than men of similar weight but having more body fat), eating at regular intervals and at the same time everyday (a study found that eating at irregular times decreased the thermic effect of food) .
So eat the right foods in the right quantity (at the right times in the day) and get moving. It’s really that simple.