What effect does an imbalance of Energy IN and OUT typically result in?

An imbalance of Energy IN (caloric intake) and Energy OUT (caloric expenditure) typically leads to weight fluctuation. When an individual's caloric intake consistently exceeds their energy expenditure, this can result in weight gain, as the excess calories are stored as fat. Conversely, if energy expenditure surpasses caloric intake over time, it can lead to weight loss. This ongoing fluctuation is a direct result of changes in diet and physical activity levels, which affect how much energy is consumed versus how much is burned.

Stable body weight occurs when caloric intake matches energy expenditure, leading to no significant weight gain or loss. In contrast, increased fitness levels typically require balanced nutrition combined with appropriate exercise, leading to improved body composition rather than simple weight change. Similarly, increased overall energy would suggest effective energy balance or a surplus in energy, rather than an imbalance that results in fluctuation. Therefore, weight fluctuation effectively captures the consequence of an energy imbalance.