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Energy balance, physical activity, and thermogenic effect of feeding in premature infants
Insights
This study found that the thermogenic effect of feeding in premature infants is approximately 3.1%, but higher when physical activity is included. Accurately measuring energy expenditure is crucial for infant growth assessment.
Area of Science:
- Neonatology
- Pediatric Nutrition
- Human Physiology
Background:
- Accurate assessment of energy expenditure is vital for understanding infant growth and development.
- The thermogenic effect of feeding (TEF) and muscular activity contribute significantly to total energy expenditure (TEE).
- Differentiating TEF from activity-related energy expenditure in premature infants is methodologically challenging.
Purpose of the Study:
- To quantify the thermogenic effect of feeding in premature infants.
- To assess the contribution of muscular activity to energy expenditure.
- To establish a reliable method for measuring TEF independent of physical activity.
Main Methods:
- Indirect calorimetry was used to measure energy expenditure in nine premature infants over two days.
- A visual activity score based on body movement was recorded concurrently.
- Energy and nitrogen balances were calculated to estimate body composition changes.
Main Results:
- Energy expenditure was significantly correlated with activity score (r=0.75 premeal, r=0.74 postmeal).
- The thermogenic effect of feeding, when isolated from activity, was estimated at 3.1% of metabolizable energy intake.
- The classical method, including postprandial activity, overestimated TEF at 9.5% of metabolizable energy.
Conclusions:
- A refined method allows for accurate estimation of the thermogenic effect of feeding in premature infants.
- Physical activity significantly influences postprandial energy expenditure, complicating direct TEF measurement.
- Understanding these components of energy expenditure is critical for optimizing nutritional support in premature infants.
Abstract:
In order to assess the contribution of the thermogenic effect of feeding and muscular activity to total energy expenditure, nine premature infants were studied for 2 consecutive days during which time repeated measurements of energy expenditure by indirect calorimetry were performed throughout the day, combined with a visual activity score based on body movement. The infants were growing at 16.6 +/- 4.0 g/kg/day (mean +/- SD) and received 110 +/- 8 kcal/kg/day metabolizable energy (milk formula) and 522 +/- 40 mgN/kg/day. Their total energy expenditure was 68 +/- 4 kcal/kg/day indicating that 41 +/- 7 kcal/kg/day was retained for growth. Based on the combination of energy + N balances it was estimated that 80% of the weight gain was fat-free tissue and 20% was fat tissue. The rate of energy expenditure measured minute-by-minute was significantly and linearly correlated with the activity score in both the premeal (r = 0.75;p less than 0.001) and the postmeal periods (r = 0.74; p less than 0.001) with no difference in the regression slope, but with a significant difference in intercept. In preset feeding schedules the latter allowed an estimation of the thermogenic effect without the confounding effect of activity. This was found to be 3.1 +/- 1.8% when expressed as a percentage of metabolizable energy intake. However when the "classical" approach was used as a comparison (integration of extra energy expenditure induced by the meal), the thermogenic effect was found to be greater, i.e. 9.5 +/- 3.8% of the meal's metabolizable energy, due to the superimposed effect of physical activity in the postprandial state.(ABSTRACT TRUNCATED AT 250 WORDS)