What Exactly is a Calorie, and What Does It Do to the Body?

calorimeterThe word “calorie” is at the very center of any weight loss discussion.  But have you ever stopped to think what a calorie actually is?  Most people will say it is the stuff in food that can make you fat, and that foods containing a lot of sugar or fat are high in calories.  True, but let’s find out more.  Getting a good handle on these topics, I believe, is helpful to staying interested in your health and thus ultimately being healthy.

In science, the calorie (symbol = cal) is the approximate amount of energy needed to raise the temperature of one gram of water by one degree Celsius.

The food and diet-related calorie is actually the kilocalorie (symbol kcal) and is the amount (1 kcal) of energy needed to raise the temperature of one kilogram of water by one degree Celsius.  However, because the kcal is used much more frequently by so many more “non-scientist” people, the kilocalorie has basically overtaken the scientific calorie’s symbol of “cal.”

So if one can of soda has 140 calories (remember, it’s really 140 kilocalories), it contains the energy to raise the temperature of about 140 kg (about 308 lbs) of water one degree Celsius.  That’s a lot of energy to me.  It’s easy to see how drinking just two of these a day can really add to weight gain.  By the way, the image at the beginning of this post shows a basic calorimeter, an instrument used to measure the amount of calories in a particular food.

But where does this energy come from in food?  Recall from grade school that the two basic forms of energy are kinetic energy and potential energy.  Kinetic energy is contained in a moving mass, like a speeding freight train.  Potential energy is stored energy; as in a drawn bow about to shoot an arrow.   Food has potential energy stored in the chemical bonds of the atoms that comprise it; namely carbon, hydrogen and oxygen.    When you eat food, your body digests it and breaks it down into its basic components of carbohydrates, fats and proteins and then further in into their individual units of glucose, fatty acids and amino acids; respectively.  As these nutrients enter your cells, they undergo one of several metabolic pathways that eventually create energy through “oxidation” where bonds are broken and energy is released.  It’s fairly complex, but this energy is what enables your cells to do their thing– divide, attack foreign invaders, make RNA and proteins, excrete waste and maintain their osmotic pressure (which prevents you from shriveling up like a prune) to name a few.

Do Calories Make You Fat?

When it comes to weight loss, it is often stated that “you need to burn more calories than take in in order for your body to lose weight.”   While this is basically true, I must warn you that there is more to healthy weight loss than just calorie counting.  The source of the calories (type of food) influences weight almost as much as the calories themselves because of the different ways the human body reacts to carbohydrates, fats and proteins.  Timing of eating is important as well.  Then, there are the many variables that determine how many calories you burn that are tied to your current state of health, body fat percentage, liver health, gut health, pre-existing medical conditions, lifestyle habits and even climate where you live.

So technically, not all calories are created equal when it comes to dieting and losing weight!  The reason for this is differing insulin response and leptin response to different types of food.  Insulin plays a central role in determining whether energy from food is burned or stored.  It drives glucose into cells for energy; stores some as glycogen in the liver and muscles, and converts excess glucose to fatty acids where they are converted into triglycerides inside adipose tissue (body fat).   Carbohydrates (sugar, fructose, grain-based carbs, starches) trigger a larger insulin surge than the slower-metabolizing fats, vegetable carbs and proteins.  Getting most of your calories from carbs will therefore keep your insulin levels comparatively high, which promotes fat storage and discourages fat burning.

If the majority of your diet for most of your life to date consisted of sugary, starchy and grain-based foods (juices, juice drinks, soda, breads, rice, cereal, pasta, bagged/boxed snacks, potatoes) you are releasing too much insulin into your bloodstream, too often.   High levels of insulin make it very difficult for your body to burn body fat for energy.   Prolonged, high levels lead to insulin insensitivity, where the cells don’t respond to insulin leading to a build up of glucose in the bloodstream; very much like a traffic backup due to an accident on the freeway.  The high levels of sugar in your bloodstream trigger the body to secrete even more insulin to try to drive the sugar into your muscles, but the effects are minimal, due to insulin insensitivity of your cells.  With high insulin levels, body fat metabolism is shut off and instead, the excess sugar is converted to increasing amounts of body fat.

If you consume a lot of fructose (high fructose corn syrup), it desensitizes leptin, the hormone that tells you when you are full, which can cause you to eat more and thus consume more calories from that particular food.  Soda is notorious for having this effect.

In summary, in order to burn excess fat you must not only consume less calories than you expend, you must also eat food that doesn’t trigger large insulin surges but rather provides steady, constant energy so that insulin levels are gradual and low, and muscle tissue is spared (i.e. your body doesn’t break down muscle for energy while you are dieting).  The best foods for this job are proteins, good fats (saturated and unsaturated– from nuts, seeds, eggs, fish, avocado, olives) and vegetable carbs (broccoli, cauliflower, stalky plants) from naturally occurring, unprocessed organic foods.  Don’t think that you can eat all the pasta, bread and desserts you want; starve yourself the next day and expect to lose weight; it won’t work.

Remember, the source of your calories matters; not just the numbers–  a calorie is NOT a calorie is NOT a calorie!

This article was originally posted in my previous blog, WeightLossMavens.

Posted in Nutrition.