Do we really burn calories?

Yes and no.  Calories are taken into the body as food is eaten.  However, the energy content in the food is significantly more potent that what the body needs.  Therefore, the body can take what we consume and break it down into very efficient molecules called adenosine triphosphate, or ATP.

ATP is the body’s energy currency.

An example of why ATP is such a good molecule can be demonstrated by the following analogy:

A student walks into the coffee shop and orders a mocha.  The drink costs $1.00, but the student only has a $100.00 bill in his/her wallet.  This bill can definitely cover the cost of the purchase, but unfortunately not in an expedient or efficient manner.  The student now needs to wait for the cashier to count out the change which takes some time.

Another student, also wanting a mocha, enters the shop and prior to buying the drink, visits an ATM and changes the $100.00 bill to twenty $5.00 bills.  When this student pays for the drink with a $5.00 bill, getting change back is much quicker.

Both students were able to pay for their drinks, but one did so in a much more efficient manner.

This occurs with the intake of calories.  Glucose (as described in the Carbohydrates’ section of this text) is the main source of the body’s energy.  Glucose is a 6-cabon molecule.  It contains enough energy to fuel many, many physiological processes in the body.  However, for a large percentage of the body’s needs, it is overkill.  It would be similar to the student using the $100.00 to pay the tab…it gets the job done but not with efficiency.  To be more efficient, the body takes the glucose and breaks it down into ATP.  In essence, it is taking the glucose to the biological ATM and changing it into $5.00 bills…similar to what the second student did.  This causes the body to have the more readily processed ATP molecules.  Because of its efficiency and effectiveness in fueling the body’s needs, ATP is called the body’s “energy currency.”

Food and Metabolism

The amount of energy that is needed or ingested per day is measured in calories. A calorie is the amount of heat it takes to raise 1 g of water by 1 °C. On average, a person needs 1500 to 2000 calories per day to sustain (or carry out) daily activities. The total number of calories needed by one person is dependent on his/her body mass, age, height, gender, activity level, and the amount of exercise per day. If exercise is a regular part of one’s day, more calories are required. As a rule, people underestimate the number of calories ingested and overestimate the amount they burn through exercise. This can lead to ingestion of too many calories per day. The accumulation of an extra 3500 calories adds one pound of weight. If an excess of 200 calories per day is ingested, one extra pound of body weight will be gained every 18 days. At that rate, an extra 20 pounds can be gained over the course of a year. Of course, this increase in calories could be offset by increased exercise. Running or jogging one mile burns almost 100 calories.

The type of food ingested also affects the body’s metabolic rate. Processing of carbohydrates requires less energy than processing of proteins. In fact, the breakdown of carbohydrates requires the least amount of energy; whereas, the processing of proteins demands the most energy. In general, the amount of calories ingested and the amount of calories burned determines the overall weight. To lose weight, the number of calories burned per day must exceed the number ingested. Calories are in almost everything one ingests, so when considering calorie intake, beverages must also be considered.

To help provide guidelines regarding the types and quantities of food that should be eaten every day, the USDA has updated its food guidelines from MyPyramid to MyPlate. It has put the recommended elements of a healthy meal into the context of a place setting of food. MyPlate categorizes food into the standard six food groups: fruits, vegetables, grains, protein foods, dairy, and oils. The accompanying website gives clear recommendations regarding quantity and type of each food that one should consume each day as well as identifying which foods belong in each category. The accompanying graphic gives a clear visual with general recommendations for a healthy and balanced meal. The guidelines recommend to “Make half your plate fruits and vegetables.” The other half is grains and protein with a slightly higher quantity of grains than protein. Dairy products are represented by a drink, but the quantity can be applied to other dairy products as well.

MyPlate
The U.S. Department of Agriculture developed food guidelines called MyPlate to help demonstrate how to maintain a healthy lifestyle.

ChooseMyPlate.gov provides extensive online resources for planning a healthy diet and lifestyle including offering weight management tips and recommendations for physical activity. It also includes the SuperTracker, a web-based application to help analyze one’s diet and physical activity.