Question

Basal Metabolic Rate depends most closely on:

• A. Lean body mass
• B. Body mass index
• C. Obesity
• D. Body surface area

Hint:

Fat is metabolically lazy; resting energy is set by metabolically active lean tissue.

Answer 1

The Correct Option is A

Step 1: Basal metabolic rate (BMR) is the energy the body uses at complete rest, in the post-absorptive state, to keep basic functions going.
Step 2: Most of this resting energy is spent by metabolically active tissue: skeletal muscle, liver, brain, heart and kidney. These tissues make up the lean (fat-free) body mass. Fat tissue is relatively inactive metabolically and contributes little.
Step 3: Because the active tissues are concentrated in lean mass, BMR correlates more closely with lean body mass than with total body weight. A muscular person has a higher BMR than a fatter person of the same weight.
Step 4: BMR has traditionally been expressed per unit body surface area, and surface area is a useful and convenient way to standardise and report BMR. But the actual physiological determinant, the tissue doing the work, is the lean body mass. The question asks what BMR depends on most closely, so lean body mass is the best answer over surface area, BMI or obesity.
Answer: Option A (Lean body mass).