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Estimation of the energy cost of physical activity in infancy
1Dunn Nutrition Unit, Cambridge.
Insights
Physical activity energy expenditure (AEE) significantly increases in infants during their first year. Energy is increasingly diverted from growth to activity, impacting energy requirements for infants.
Area of Science:
- Pediatric Nutrition
- Infant Metabolism
- Energy Balance
Background:
- Accurate estimation of energy expenditure is crucial for understanding infant growth and nutritional needs.
- Physical activity energy expenditure (AEE) is a significant component of total energy expenditure in infants.
- Limited data exists on AEE in free-living infants throughout the first year of life.
Purpose of the Study:
- To quantify physical activity energy expenditure (AEE) in healthy, free-living infants.
- To analyze the changes in AEE as a proportion of energy intake during the first year of life.
- To provide data aiding in the factorial estimation of infant energy requirements.
Main Methods:
- A mixed longitudinal study involving 124 healthy infants.
- 232 estimations of AEE were conducted between 1.5 and 12 months of age.
- Total energy expenditure and body composition were measured using the doubly labeled water technique; sleeping metabolic rate was predicted from weight.
Main Results:
- Physical activity energy expenditure (AEE) increased from 5% of energy intake at 1.5 months to 34% at 12 months.
- Growth costs decreased by 90% over the study period.
- Metabolisable energy intake decreased by only 20% from 1.5 to 12 months.
Conclusions:
- Infants progressively divert more energy towards physical activity as they grow.
- These findings on AEE can inform the estimation of energy requirements in infant populations.
- Further research is needed to understand individual variability in AEE and the impact of various health conditions.
Objective:
To estimate physical activity energy expenditure (AEE) in groups of free living infants in the first year of life.
Design:
Mixed longitudinal study of 124 healthy infants, using 232 estimations of AEE made between 1.5 and 12 months. Infants studied at more than one time point were treated as new cross sectional data points. Total energy expenditure and body composition were estimated using doubly labelled water. Sleeping metabolic rate was predicted from weight.
Results:
AEE increased from 5% of energy intake at 1.5 months to 34% at 12 months. Growth costs declined by 90%, but metabolisable intake by only 20%, over the same period.
Conclusions:
Energy is increasingly diverted from growth to activity during infancy. Values for AEE may aid in estimating energy requirements of groups factorially. Further work is required, however, on individual variability in AEE, and on the effects of disease, hospitalisation, surgery, and malnutrition.