Weight is, in reality, a rather straightforward result of the Calories taken in versus the Calories expended. It follows the dictum "Input equals output plus accumulation." If weight is constant (i.e., accumulation = 0), the Calories being consumed must equal the calories being expended. The Calories expended depend on a person's activity level (greater activity requires more Calories), the current weight (sustaining higher weights requires more Calories), whether male or female (females require about 10% fewer calories to maintain a given body weight at the same activity level), and your genetic heritage.

If fewer Calories are consistently consumed than are required to maintain a person's current weight, weight will steadily decrease until the Calories required to sustain the lower weight again equal the Calories being consumed. Since one pound of body fat (indeed, all fat) contains 3,500 Calories, each accumulated 3,500 Calorie deficit (or increase) in Calorie consumption versus that required for weight maintenance will translate directly into a weight change of one pound.

The implications of this scientific fact are simple to calculate. For example, one slice of regular white bread contains about 80 calories. If weight has been constant, indicating a balance between calories consumed and expended, and the daily food intake is increased by one slice of bread while maintaining the same activity level, a gain of one pound will occur in about 3500/80=43.75 days. Since there are a little over eight 44 day periods in one year, one might conclude that an extra single slice of bread daily would cause a weight gain of eight pounds in one year. This is not the case, however, since as weight increases some of the 80 calories from the extra slice of bread will be needed to sustain the higher weight rather than be stored as extra body fat. Weight2Weight provides a more accurate estimate of the weight change at any point in time for a given calorie per day change.

Example 8: Select [English] Units, [Male] Sex, [HarBenMcArd] Cal/day/lb and [Sedentary] Activity level. Enter "175.0" for [Current weight], "70" for Height and "37" for Age. Select the [Current weight] checkbox.and click the [Calories/day] button to display 2156 Calories/day.

Tab to [New Cal/day] and enter 2236 (the 80 Calories/day increase), select the [New Cal/day] check box and click the [New weight] button to show 185.7 lbs (+ 10.7 lbs), the weight sustained by 2236 Calories/day.

This is the weight that will ultimately be reached due to increasing the daily Calories by 80. Open the Projection panel, select # Days, enter 365 for [# Days] and click [Calculate] to show the weight of 180.8 lb and a BMI of 25.9 after one year, or a gain of about 5.6 lbs of the eventual 10.7 lbs the extra 80 Calories/day will eventually add.

Figure 7. Results from Example 8

Activity Level (Exercise)

Exercise is good. Experiment with the different activity levels to see what exercise can do for a weight loss program. For many people it is more efficient to concentrate on caloric intake to manage weight, and take the benefits of exercise in health and well-being.

Another Comment

The other two main sources of dietary calories besides fat are carbohydrates (breads, potatoes, etc.) and protein (meat, cheese, etc.). While one pound of fat contains 3500 Calories, one pound of either carbohydrates or protein contains about 1555 Calories. Fat is also already in the form the body uses to store excess Calories, while carobhydrates and protein Calories must be converted to fat for storage. Thus, a focus on fat consumption can generally be more efficient in managing body weight. Mom was right - eat those vegetables!