If you've ever experienced the "plateau" stage of a weight loss program, you understand how discouraging this can be. A plateau is a phase during a weight loss program where weight refuses to budge in spite of a negative energy balance - or more energy being expended through exercise than taken in via calories.

Researchers suggest that this common phenomenon is due to the way our bodies are programmed. The human body is well equipped to conserve energy during periods of famine; that is, if food is not plentiful, our bodies are able to maintain weight and energy by slowing the metabolism. This mechanism of food conservation worked for ancient civilizations, when people were hunter-gatherers and food was not always available.

But in today's environment of excess food consumption and inactivity, the human body is not equipped to speed up metabolism to work off the extra pounds.

While there is no perfect answer for moving past a plateau phase, experts recommend increasing the intensity or duration of exercise or adding different types of exercise to your current exercise program.