Erratum: Estimating energy expenditure in mice using an energy balance technique

Correction to: International Journal of Obesity (2013) 37, 399–403; doi:10.1038/ijo.2012.105; published online 3 July 2012

Since the online publication of this article it has been brought to our attention that two items in the manuscript need clarification or correction. These amendments do not change the inferences reached. We thank KD Hall (NIH) for bringing these points to our attention.

The error has now been rectified and the corrected article appears in this issue. The html and online pdf versions have also been rectified and now carry the corrections.

The authors would like to apologise for this error.

1. Clarification

Equation 2 posits:

Assuming that changes (Δ) in somatic chemical energy content are calculated as initial minus final during the period of TEE_bal (as we did), this equation is correct.

However, as Equation 2 is actually a restatement of Equation 1:

for consistency and clarity, Equation 2 should read MEI minus changes in somatic energy content:

with changes in body composition calculated as final −initial (FM or FFM) of the period of TEE_bal. Both formulations of course give the same result, but the Equation 2 revised is more intuitive and is consistent with the form of Equation 1 (also see¹).

2. Correction

In the paragraph entitled ‘Estimates of TEE using energy balance (TEE_bal)’, before Equation 2, we state that ‘The energy cost of depositing dietary calories as somatic tissue is greater than that released by their oxidation. We assigned 13.2 kcal for each gram of fat mass (FM) gained, and 9.0 kcal for each gram of FM lost; 2.2 kcal for each gram of fat-free mass (FFM) gained and 1.0 kcal for each gram lost.’ This differential assignment of energy costs of tissue anabolism/catabolism—and the adjustments in TEE_bal deriving from their application— are not necessary for the calculation of TEE_bal. As TEE_bal is calculated directly from MEI and changes in somatic mass and composition, energy costs related to tissue deposition or mobilization are inherently accounted for by these independent variables. Thus, in the present case, fixed, equal caloric equivalents of FM and FFM can be assigned to gains or losses of somatic mass.²

Assigning caloric equivalents for FM=9.4 kcal g⁻¹ and FFM=1.0 kcal g⁻¹ gained or lost,^{3, 4} we recalculated TEE_bal using Equation 2 revised. As expected, this simplified estimate of TEE_bal has minimal effects in the current study owing to the relatively small change in body mass among the different groups: for example, mean differences (between TEE_bal and TEE_IC) for the two techniques (revised Figure 1d) were only 2.3% higher in DIO-AL, 1.1% higher in DIO-WR, 1.0% higher in CON-AL and 0.9% higher in CON-WR for the recalculated versus original values (see revised Figure 1d). Likewise, the correlations of TEE by balance and calorimetry were essentially unaffected: R²=0.8754 in original calculation (Figure 1b) and R²=0.8686 in the revised calculation (revised Figure 1b).