Adult basal metabolic rate decreases with an increase in?

Appeared in: AIIMS BBSR SNO - 2019

Explanation

The question asks which factor, upon increasing, causes a decrease in the basal metabolic rate (BMR).
Body fat (adipose tissue) is metabolically less active compared to lean muscle mass.
Therefore, as the proportion of body fat increases relative to muscle mass, the overall energy expenditure at rest (BMR) decreases.
An individual with a higher percentage of body fat will have a lower BMR than a person of the same weight with more muscle.

Option A: An increase in muscle mass increases BMR. Muscle tissue is metabolically active and requires more energy to maintain, even at rest.
Option B: Fever significantly increases BMR. The body's metabolic processes speed up to fight infection, raising the core temperature and energy expenditure.
Option D: An increase in body surface area increases BMR. A larger body has more surface area from which to lose heat, so the body must expend more energy to maintain its core temperature.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Factors affecting Basal Metabolic Rate (BMR) as background academic context rather than a clinical decision trigger.
Understanding BMR is crucial for nurses when planning diets and calculating caloric needs for patients, especially for weight management, nutritional support, and managing metabolic disorders.
A patient's body composition (fat vs. muscle) is a more accurate predictor of their metabolic needs than weight alone. This is why athletes can consume more calories without gaining weight compared to sedentary individuals.
What if? If a patient develops a high fever (e.g., 102°F), their BMR and caloric needs will increase significantly. The nurse must ensure adequate hydration and nutrition to meet this increased metabolic demand and prevent catabolism (breakdown of body tissues).

How to Approach the Question

First, understand the definition of Basal Metabolic Rate (BMR): the energy used for basic life-sustaining functions at rest.
Analyze the question's core relationship: it asks what factor decreases BMR when that factor increases.
Evaluate each option's effect on metabolic activity:
Muscle: Is it active or inactive tissue? (Active -> increases BMR)
Fever: Does it represent a state of higher or lower bodily activity? (Higher -> increases BMR)
Body fat: Is it as active as muscle? (Less active -> decreases BMR)

Concept Tested & Keywords

QgxVA_pHP3V58LPm-2n1NB

E6 Nutrition Monika Sharma 3e p. 74-76

E6 textbook of Applied Biochemistry and Nutrition & DieteticsHarbans Lal (pp 26-464 of 479) p. 263-265

E6 Biochemistry U Satyanarayana— Part 2 (pp 421-820 of 840) p. 128-130

Practise the full AIIMS BBSR SNO - 2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.