ACE Health Coach Certification Practice Test

What is the primary reason for variability in basal metabolic rate between individuals?

1. nonexercise activity thermogenesis

2. passive overeating

3. differences in lean body mass

4. active overeating

The correct answer is: differences in lean body mass

The primary reason for variability in basal metabolic rate (BMR) between individuals is differences in lean body mass. BMR is the amount of energy expended while at rest, and it largely depends on the body's composition. Lean body mass, which includes muscles, organs, bones, and other non-fat tissues, is metabolically active and requires more energy to maintain than fat mass. Individuals with a higher percentage of lean body mass will have a higher BMR because their bodies require more calories for the maintenance and function of muscle tissue compared to fat tissue. This is why bodybuilders, for example, tend to have higher metabolic rates compared to individuals with more body fat. Factors like age, sex, genetics, and hormonal levels can also influence the amount of lean body mass a person has, subsequently affecting their BMR. Although nonexercise activity thermogenesis, passive overeating, and active overeating can influence overall energy expenditure and weight gain, they do not directly account for the baseline metabolically active tissue that primarily dictates BMR variability among individuals.