During febrile disorder like typhoid BMR .......... by .......... %.

Question

Accepted Answer

The correct option is 1:
The correct answer is **increases, 7**. The physiological response of the human body to a fever, such as the one experienced during a febrile disorder like typhoid, is a marked rise in the Basal Metabolic Rate (BMR). The BMR represents the minimum amount of energy (calories) required to maintain vital functions when the body is at rest. When an infection triggers a fever, the body’s thermoregulatory center in the hypothalamus resets its temperature 'set-point' to a higher level. To reach this new, higher temperature, the body must generate more heat, which requires an increase in metabolic activity, or catabolism. This surge in heat production is the body’s natural defense mechanism to inhibit microbial growth and enhance the immune response. A well-established clinical and physiological rule of thumb indicates that for approximately every $0.5^\circ \text{C}$ rise in body temperature, or approximately $1^\circ \text{F}$, the BMR increases by roughly 7%. Therefore, during a febrile state, the metabolic demands on the body increase significantly, consuming more calories and oxygen just to sustain the elevated core temperature.

The incorrect option is 2:
The option "decreases, 7" is incorrect because a febrile disorder fundamentally **increases** the body's metabolic activity, it does not decrease it. The body is actively expending more energy to generate heat and raise its core temperature to fight the infection. A decrease in BMR would be associated with conditions like hypothyroidism or severe starvation, where the body attempts to conserve energy, which is the opposite of the energy-intensive process required to maintain a fever. Furthermore, the concept of metabolic depression in illness is typically observed in states of hypothermia, not the hyperthermia associated with fever.

The incorrect option is 3:
The option "decreases, 15" is incorrect for the same reason as option 2: fever causes the BMR to **increase**, not decrease. The body's immediate and persistent requirement during an infection is to mobilize energy and heat, which necessitates a higher metabolic rate. A 15% decrease would represent a substantial drop in resting energy expenditure, which would severely compromise the body's ability to maintain core functions and mount an effective immune response against a systemic infection like typhoid.

The incorrect option is 4:
The option "increases, 15" is factually plausible for a high fever, as a rise of approximately $1^\circ \text{C}$ (or $1.8^\circ \text{F}$) can increase the BMR by 10% to 13%. Therefore, a $1.5^\circ \text{C}$ rise could easily result in a 15% increase. However, in the context of a general scientific rule or a typical increment used in foundational exams, the figure of 7% for a standard fever increment is the most precise and commonly referenced value (representing approximately a $0.5^\circ \text{C}$ increase). Since the question is a multiple-choice single-correct answer, the option pairing the known process (increase) with the standard incremental percentage (7%) is the better fit.