How does metabolic adaptation occur during weight loss?

During weight loss, metabolic adaptation typically occurs as the body adjusts its energy expenditure in response to reduced calorie intake and body mass. As individuals lose weight, the body shifts into a more energy-efficient state. This results in a decrease in the basal metabolic rate (BMR) as the body conserves energy due to the lower energy availability.

This reduction in energy expenditure is a survival mechanism developed over evolutionary time, allowing the body to function with less energy to cope with periods of food scarcity. Therefore, as weight decreases, the metabolic rate adapts accordingly, leading to a lower energy expenditure than would be expected for an individual with a higher body weight.

In contrast, the other choices do not accurately represent the physiological responses that accompany weight loss. For instance, stating that the body increases energy expenditure during weight loss contradicts the principles of metabolic adaptation. Similarly, saying that metabolism remains unchanged or that weight loss has no effect on metabolic rate ignores the significant research that shows how metabolic variables can shift in response to weight changes.