Examining variations of resting metabolic rate of adults: a public health perspective

Abstract

Purpose: There has not been a recent comprehensive effort to examine existing studies on the resting metabolic rate (RMR) of adults to identify the effect of common population demographic and anthropometric characteristics. Thus, we reviewed the literature on RMR (kcal·kg(-1)·h(-1)) to determine the relationship of age, sex, and obesity status to RMR as compared with the commonly accepted value for the metabolic equivalent (MET; e.g., 1.0 kcal·kg(-1)·h(-1)).

Methods: Using several databases, scientific articles published from 1980 to 2011 were identified that measured RMR, and from those, others dating back to 1920 were identified. One hundred and ninety-seven studies were identified, resulting in 397 publication estimates of RMR that could represent a population subgroup. Inverse variance weighting technique was applied to compute means and 95% confidence intervals (CI).

Results: The mean value for RMR was 0.863 kcal·kg(-1)·h(-1) (95% CI = 0.852-0.874), higher for men than women, decreasing with increasing age, and less in overweight than normal weight adults. Regardless of sex, adults with BMI ≥ 30 kg·m(-2) had the lowest RMR (<0.741 kcal·kg(-1)·h(-1)).

Conclusions: No single value for RMR is appropriate for all adults. Adhering to the nearly universally accepted MET convention may lead to the overestimation of the RMR of approximately 10% for men and almost 15% for women and be as high as 20%-30% for some demographic and anthropometric combinations. These large errors raise questions about the longstanding adherence to the conventional MET value for RMR. Failure to recognize this discrepancy may result in important miscalculations of energy expended from interventions using physical activity for diabetes and other chronic disease prevention efforts.

FIGURE 1

Adjusted mean with 95% CI for the RMR (kcal·kg⁻¹·h⁻¹) for adults from 351 publication estimates presented by nine age groupings and sex. The number of publication estimates in each category is included on the x-axis for men (M) and women (W). Solid line = 1.0 kcal·kg⁻¹·h⁻¹.

FIGURE 2

Adjusted mean with 95% CI for the RMR (kcal·kg⁻¹·h⁻¹) for adults from 278 publication estimates, based on BMI (kg·m⁻²) categories of normal (< 25), overweight (25–29.9), and obese (≥ 30) adults presented by sex. The number of publication estimates in each category is included on the x-axis for men (M) and women (W). Solid line = 1.0 kcal·kg⁻¹·h⁻¹.

FIGURE 3

Adjusted mean with 95% CI for the RMR (kcal·kg⁻¹·h⁻¹) for adults from 266 publication estimates, presented by sex, three age groupings, and BMI. The number of publication estimates for BMI groups is included on the x-axis for normal weight (Nm), overweight (Ov), and obese (Ob). Solid line = 1.0 kcal·kg⁻¹·h⁻¹.