Background

The high rates of under-reporting of energy intake (EI) in pregnancy increase the need to estimate EI with a validated mathematical equation as a function of weight and energy expenditure (physical activity, resting metabolic rate [RMR]). Physical activity can be measured with activity monitors, but RMR is almost exclusively estimated from a validated equation. A novel mobile metabolism device, Breezing, allows for feasible RMR assessments, and may improve accuracy of back-calculated EI. This study compared how back-calculated EI estimates varied when using the mobile Breezing device vs. equations to estimate RMR.

Methods

Pregnant women with overweight/obesity (N=16; pre-pregnancy BMI M= 32.1) participating in an intervention to manage prenatal weight gain completed daily (Aria Wi-Fi weight, Jawbone physical activity) and weekly (Breezing RMR) measures from ~9-36 weeks gestation. Daily EI (kcal) was back-calculated using estimated RMR vs. Breezing RMR; weekly data were averaged by pregnancy Trimester 1, 2, and 3. Paired t-tests, equivalency tests, and correlations were used to analyze means and associations.

Results

Means for back-calculated EI (kcal) with estimated vs. Breezing RMR were Trimester 1: 2390 vs. 2456, Trimester 2: 2651 vs. 2770, and Trimester 3: 2715 vs. 2699; estimated EI’s were equivalent (p’s>0.05). Back-calculated EI using estimated vs. Breezing RMR were significantly correlated at Trimester 1, 2, and 3 (r=0.71-0.86, p<0.05).

Conclusions

The calculation of EI between estimated RMR vs. Breezing RMR were equivalent, suggesting estimated and Breezing RMR are both sufficient in estimating EI. However, more research is needed to replicate these findings among women with wider variability in weight status (e.g., normal weight, severe obesity) to confirm our findings.