Tuesday February 7 2012
A small study found spoon-fed babies more likely to be obese
“Spoon feeding makes babies fatter,” the BBC reported today. According to the broadcaster, babies weaned on pureed food tend to end up fatter than infants whose first tastes are finger foods.
This high-profile news is sure to be of interest to parents. However, the research behind the coverage is not strong enough to support such claims. The study compared information gathered on the diet and BMI of 92 child weaned on finger foods (“baby-led” weaning) and 63 children weaned using spoon-feeding. In total, 10 spoon-fed children were above a healthy weight compared to nine in the baby-led weaning group. However, the reliability of the research is undermined by a number of shortcomings, such as the small number of children studied (just 155), the fact that most children in each group had a normal weight and because the study looked at eating habits at a single point in time, rather than recording them over time.
Overall, the study does not support the various claims in the media that spoon-feeding makes babies fatter or encourages a sweet tooth, or that baby-led weaning makes children healthier. It is possible, for example, that a child’s food preferences might influence how they end up being weaned, or even that the results are due to chance. Examining the issue will require larger studies which look at children’s eating and weight over time.
Where did the story come from?
The study was carried out by researchers from the University of Nottingham, which also funded the research. The study was published in the peer-reviewed medical journal BMJ Open.
The study was reported uncritically in most papers, with quotes from independent experts who reportedly supported its findings.
What kind of research was this?
This small cross-sectional study examined the association between weaning method, food preferences and frequency of food consumption. The researchers were also interested in how heavy the children were for their height (body mass index or BMI) and whether they were “picky eaters”. The researchers say that at present, little evidence is available on the possible impact of different weaning methods on food preferences and health, but that baby-led weaning is associated with “reduced maternal anxiety” about feeding and “a maternal feeding style that is low in control”.
This study compared two groups of parents who used different weaning methods for their children and looked at their children’s food preferences and BMI. However, it cannot prove cause and effect, nor can it show that baby-led weaning results in healthier food choices and healthier weight. A more reliable method of assessing this question would be a randomised controlled trial in which parents were randomly allocated one of the two weaning methods to use, and their babies followed over a period of time to see whether weaning method led to differences in dietary preference or BMI. However, such as trial may have ethical and feasibility issues.
Alternatively, a prospective study that followed children weaned by the two methods over a period of time would also be preferable to a cross-sectional study, which only looks at weaning methods, children’s food preferences and other factors at one point in time.
What did the research involve?
The researchers recruited the parents of 155 children aged 20-78 months between June 2006 and January 2009. The group that used baby-led weaning were recruited by advertising on the internet while those who used spoon-feeding were recruited from the researchers’ own laboratory database.
All the parents completed a standard questionnaire which asked about:
- their infants’ feeding and weaning style
- their infants’ preferences for 151 foods (with ratings from 1 “loves it” to 5 “hates it”) – the preferences were then analysed by standard food categories, such as carbohydrates, proteins and dairy, and there was also a category for whole meals, such as lasagne
- their frequency of consuming particular foods (with ratings from 1 “more than once a day” to 7 “less than once a month”)
- whether they would classify their children as picky eaters
- the children’s height and weight
The parents’ socioeconomic status was also assessed using validated measures.
The researchers pointed out that because no formal definition of weaning exists, they used the parents’ own reports of weaning styles to divide parents into two groups. To try to verify these self-reported methods, they also questioned some parents in more detail about weaning.
As the baby-led weaning group tended to be younger than the spoon-fed group, the researchers carried out their analyses on food preferences and weaning method using a sub-sample of 74 infants – 37 from the spoon-fed group matched by age to 37 from the baby-led weaning group. They used the whole sample for all other analyses.
What were the basic results?
The general trend in results was as follows:
- Carbohydrates were the most popular food category for the baby-led weaning group, who liked carbohydrates more than the spoon-fed group.
- Sweet foods were most liked by the spoon-fed group.
- Preference and frequency of consumption were not influenced by socioeconomic status, although an increased liking for vegetables was associated with a higher social class.
- Using NHS BMI guidelines, eight children in the spoon-fed group were obese (12.7%) compared to none in the baby-led group. However, nine children in the baby-led weaning group (14.3%) were overweight compared to two in the spoon-fed group (3.2%).
- Three children in the baby-led weaning group were classed as underweight (4.7%) compared to none in the spoon-fed group.
- No difference in picky eating was found between the two groups.
How did the researchers interpret the results?
The researchers concluded that “weaning style impacts on food preferences and health in early childhood.” They say their results suggest that the baby-led approach to weaning helps infants learn to regulate their food intake in a way that leads to healthier weight and a preference for healthy foods, such as carbohydrates.
While it was widely reported, this small cross-sectional study proves very little about the possible impact of different weaning methods on children’s food preferences, BMI or other health outcomes. Instead, because of its cross-sectional design, it can provide only a snapshot of all these factors (as reported by parents) at one point in time. It cannot show, for example, that babies who prefer carbohydrates do so because they were weaned on finger foods, as some news sources have reported.
Many factors can affect a child’s food preferences and BMI, including genetic factors, exercise and social and demographic background (which was indicated to a degree by the fact that higher socioeconomic status was associated with higher vegetable intake). Though the study found differences in the BMI status of the children, the small sample size makes it difficult to draw reliable comparisons between the groups. For example, though eight children were obese in the spoon-fed group and none in the baby-led group, this finding could be due to chance. Also, when overweight and obese children were combined, ten children in the spoon-fed and nine in the baby-led groups were overweight or obese. This raises the strong possibility that there would be no real difference in BMI if a much larger group of children were looked at.
With rising rates of childhood obesity, the issue of how best to wean and how this might affect children’s attitudes to food and their long-term health is of concern to parents. However, a large-scale prospective study that follows babies for several years would be a much better way to shed light on the issue.