Too Many, or Too Few Calories? Help

By — McGraw-Hill Professional
Updated on Aug 30, 2011

Introduction to Too Many, or Too Few Calories?

We talked about the Chemical Balance of Life, and its relationship to cellular respiration or metabolism. Recall that in the catabolism (breakdown) of chemical foodstuffs (such as glucose molecules), free or kinetic energy is released and tied to the production of more cell ATP. Obviously, these topics are closely related to our current discussion, since digestion is, in fact, defined as the chemical and physical breakdown of food. Similarly, nutrition is the process of nourishing or feeding the body cells.

The Concept Of Calories

The nutrients that humans eat, say, in a candy bar, are all associated with a certain number of calories ( KAL -or- ees ). A calorie is technically a unit for describing the amount of “heat” (calor) that is released during the break-down of food. In nutrition, we generally use the “large calorie” or kilocalorie ( KILL -uh- kal -ur-ee) – the amount of heat energy released measured in “thousands” (kilo-) of calories. A candy bar, for instance, may contain 670 kilocalories of heat energy, when it is consumed.

The Concept Of Caloric Balance

An important principle of Biological Order in humans and other animals is the notion of caloric (kuh- LOR -ik) balance. Caloric balance is a condition where the number of kilocalories consumed in food per day exactly equals the number of kilocalories burned in exercise per day. Summarizing, we have:

CALORIC BALANCE : Number of kilocalories consumed/day = Number of kilocalories burned/day

Caloric balance is desirable, therefore, whenever we wish to maintain our current body weight. It logically follows that whenever one wishes to either gain or lose weight, then some degree of Biological Disorder must be inserted into the scheme, such that the caloric balance is disrupted.

When the number of kilocalories consumed per day significantly exceeds the number burned during exercise, there is a net excess of kilocalories. Some of these excess kilocalories are stored as extra glycogen deposits in liver and muscle cells, and some of it is stored as extra lipid within our adipose tissue cells. The net result, of course, is that we (gulp!) gain weight and often get fatter!

Conversely, to lose weight, the number of kilocalories burned during daily exercise must exceed the number consumed in foodstuffs (no matter what the current fad diet books tell you!).

Practice problems for these concepts can be found at:  Nutrition And The Digestive System Test

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