Final answer:
True, a calorie-restricted diet can reduce basal metabolic rate (BMR), making it harder to lose weight over time. This adaptation helps conserve energy during reduced intake, but it also means that after significant dieting, additional weight loss efforts may be less effective.
Step-by-step explanation:
True, weight loss that results from a calorie-restricted diet can indeed lead to a decrease in metabolic rate. When an individual consistently consumes fewer calories than their body needs, the body adjusts by decreasing its basal metabolic rate (BMR), an adaptive mechanism to conserve energy. As a result, the body becomes more efficient in utilizing energy from the restricted intake, leading to a reduced rate of weight loss over time. The impact on BMR is more pronounced when the calorie restriction is severe or combined with a decrease in physical activity. Moreover, the body’s efficiency in converting internal energy to work during exercise is low, meaning that more internal energy is lost than the work accomplished, which also contributes to weight loss. However, once the body adjusts to the lower calorie intake, the metabolic rate decreases, making further weight loss challenging.
It has been observed that after significant dieting, subsequent attempts to lose weight become less effective since the body alters its response to lower energy levels by reducing the BMR. Furthermore, prolonged fasting or serious calorie reduction can lead to a significant drop in BMR, sometimes as much as 30%, as seen in cases of starvation or very restrictive diets.