VANCOUVER, British Columbia — Two-month-old infants who are bottle-fed exclusively with super-sized bottles consume, on average, an extra 4 ounces of formula per day, new research shows.

That equates to about a gallon of extra formula of month, and an excess caloric burden of 5% to 20%. Given that studies increasingly show a link between early childhood obesity and later obesity, this could have ramifications for bottle-fed infants.

"It was a cross-sectional study, so all we could find was an association, but it does seem like bottle size is related to the amount of formula that's given to an infant, and that could have implications for the future. But we do need to look at this longitudinally" to confirm the results, said lead investigator Charles Wood, MD, a primary care research fellow and clinical instructor at the University of North Carolina at Chapel Hill.

He presented the findings here at the Pediatric Academic Societies and Asian Society for Pediatric Research Joint Meeting.

Encouraging the use of smaller bottles for formula-fed infants "is a very practical approach to help families not overfeed their babies," said Sheila Gahagan, MD, MPH, professor of pediatrics at the University of California at San Diego, who attended the presentation.

While conducting the GreenLight study — a cluster randomized trial aimed at preventing childhood obesity conducted at 4 pediatric resident clinics — the researchers noted that some parents fed infants from bottles that were larger than recommended.

"We couldn't find any evidence that bottle size had been looked at as a predictor of obesity. A lot of research compares breast-feeding with bottle-feeding, but there's not a lot of information on infants who are exclusively formula-fed," said Dr. Wood.

The team conducted a cross-sectional analysis of baseline data for infants involved in the GreenLight study who were exclusively formula-fed. They collected reports from caregivers on volume consumed per feed, the number of feeds per day, and bottle size.

The researchers used log-transformed ordinary least-squares regression to determine the association between bottle size and total volume of feed, after adjustment for caregiver race/ethnicity, income, infant birth weight, age in weeks, sex, and enrollment in the US Department of Agriculture Women, Infants, and Children (WIC) program. Concerns arose about confounders, so the researchers used secondary logit models to identify determinants of bottle size used.

In the GreenLight study cohort, 44% of the 2-month-old infants were exclusively bottle-fed. Of those 378 infants, 18% were white, 27% were black, and 51% were Hispanic.

In addition, 69% of the infants were fed with bottles smaller than 8 ounces and 31% were fed with bottles larger than 8 ounces.

The number of feeds per day was lower with the large bottle than with the small bottle (6.8 vs 7.5). However, more formula was consumed by infants fed with the large bottles (33.5 vs 29.4 oz; P < .01).

After adjustments, infants fed with large bottles were found to consume 14% more formula per day than infants fed with small bottles (P = .03).

I like the practicality of recommending the smaller bottle.

On secondary analysis, there was no association between bottle size and sex, birth weight, income, race/ethnicity, age in weeks, or WIC enrollment.

"What was surprising was the amount of additional formula consumed. If you look at a month, that's a gallon of extra formula. That's a lot of extra calories," said Dr. Wood.

In fact, the excess could amount to a 5% to 20% overage, said session moderator Larry Yin, MD, associate professor of clinical pediatrics at the Keck School of Medicine at the University of Southern California and a researcher at Children's Hospital of Los Angeles.

"From the WIC data, we're seeing that weight even at very young ages is starting to impact weight in the future," Dr. Yin told Medscape Medical News. And these infant data "may follow that."

But bottle size might not be the only factor to consider, according to Dr. Gahagan. "It would be great to do more coaching about how to watch babies' cues indicating they're satisfied, although that's a little harder to do," she said.

"I like the practicality of recommending the smaller bottle. For newborns in the hospital, we use 2 ounce bottles." Maybe there could be a graduated system, she said. "When they come for the 6-week checkup, we can tell caregivers whether they're ready for the 6-ounce bottle."

In the future, the researchers plan to determine whether larger bottle size predicts rapid infant weight gain or obesity longitudinally, and whether encouraging caregivers to use smaller bottles is a useful intervention.

Dr. Wood, Dr. Gahagan, and Dr. Yin have disclosed no relevant financial relationships.

Pediatric Academic Societies (PAS) and Asian Society for Pediatric Research (ASPR) Joint Meeting: Abstract 1155.6. Presented May 3, 2014.


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