BMR is decreased in:
**Core Concept**
The basal metabolic rate (BMR) is the amount of energy expended by the body at rest, representing the body's metabolic activity. It is influenced by factors such as age, sex, weight, and thyroid function.
**Why the Correct Answer is Right**
A decrease in BMR is often associated with hypothyroidism, a condition characterized by underactive thyroid gland. In hypothyroidism, the thyroid gland does not produce enough thyroid hormones, which are essential for regulating metabolism. Thyroid hormones stimulate the breakdown of nutrients to produce energy, and a decrease in their production leads to a decrease in BMR. This is because thyroid hormones increase the activity of enzymes involved in cellular respiration and enhance the transport of oxygen and glucose into cells.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because aging is associated with a decrease in BMR, but it is not the correct answer because the question asks for a specific condition that causes a decrease in BMR.
**Option B:** This option is incorrect because starvation is associated with an increase in BMR due to the body's attempt to break down stored fat for energy.
**Option C:** This option is incorrect because obesity is associated with an increase in BMR due to the body's increased energy expenditure to maintain its larger size.
**Clinical Pearl / High-Yield Fact**
A classic exam trap is to remember that a decrease in BMR is associated with hypothyroidism, and an increase in BMR is associated with hyperthyroidism, starvation, and obesity.
**Correct Answer:** D. Hypothyroidism.