Tuesday July 1 2014
KFC was one fast food brand not assessed in these studies
“Children who recognise fast food brands are more likely to be obese,” the Mail Online reports.
The headlines are based on a US study that included two separate samples of children aged three to five years; the first contained 69 children and the second contained 75.
In both studies, the parents were questioned about their child’s TV viewing and physical activity levels.
The children themselves were asked to complete a picture collage designed to assess “brand recognition” of four major brands: McDonalds, Burger King, Coca-Cola and Pepsi.
In the first study, they also had to assess two crisp brands (Fritos and Doritos) and two breakfast cereals (Lucky Charms and Trix). In the second study, they had to assess two sweet brands (M&Ms and Jelly Belly) and two different breakfast cereals (Froot Loops and Fruity Pebbles).
The researchers then looked at how these responses were associated with child body mass index (BMI).
In both groups, increased brand knowledge was significantly associated with increased BMI.
However, this study has many limitations, such as its small sample size and reliance on self-reporting.
Despite this, the study still makes for interesting reading. Better understanding about the influences on child consumption patterns may help towards developing effective measures to target the growing obesity epidemic.
Where did the story come from?
The study was carried out by researchers from the University of Oregon, Michigan State University and Ann Arbor Public Schools Preschool and Family Center, in the US. No sources of financial support are reported. The study was published in the peer-reviewed medical journal Appetite.
The Mail Online’s reporting of the study is accurate, but does not consider the wider limitations of this very small study and limited analysis.
The news website also mentions Kentucky Fried Chicken (KFC), despite this brand not being assessed during the two studies.
What kind of research was this?
This was a cross-sectional analysis, using data from two small studies of young children, assessing their knowledge of brands high in fat, sugar and salt. Researchers also asked parents about their children’s TV viewing habits and physical activity levels. They then looked at how these were associated with the children’s BMI.
The researchers say how previous research has shown that older children/teenagers who are obese were usually overweight or obese in nursery school.
They discuss how understanding the way in which a child’s palate develops with exposure to calorie-dense, nutrient-poor foods may contribute to an understanding of how food consumption patterns in early childhood influence weight. The researchers also discuss the role of influences such as brand logo recognition, activity patterns and television viewing patterns (e.g. “mindless” eating in front of the TV).
The present research aimed to address three research questions:
- Does exposure to commercial television significantly influence pre-school children’s BMI scores?
- Does knowledge of packaged food and beverage brands significantly influence pre-school children’s BMI scores?
- Does the amount of daily physical activity counteract the effect of brand knowledge or commercial television exposure on pre-school children’s BMI scores?
Understanding these influences and patterns may help develop measures to tackle obesity.
What did the research involve?
The researchers’ questions were addressed in two separate studies.
The first study involved 69 children (34 boys and 35 girls) aged three to five years, as well as one parent of each child. The sample contained people of a diverse ethnic mix. Parents were asked how many hours a week their child spend watching commercial TV and non-commercial TV (e.g. DVDs), and how many days a week their child engages in 30 minutes or more of physical activity.
The brand knowledge task then involved asking children to sort picture cards to create collages that showed their knowledge of different food and drink brands, and which brands were competitors of each other. The task included four groups: fast food (McDonald’s “versus” Burger King), soft drinks (Coca-Cola “versus” Pepsi), crisps (Fritos “versus” Doritos) and breakfast cereal (Lucky Charms “versus” Trix).
Their results for each of the four food groups were scored on a scale from 0 to 18, with higher scores indicating more brand knowledge.
They used a statistical model to see how age and gender-specific BMI correlated with their responses.
This study included 75 children (40 boys and 35 girls), also aged three to five, as well as one parent of each child. Again, the sample contained people of a diverse ethnic mix. Parents were asked the same questions on TV viewing and physical activity. Children were asked the same brand knowledge questions for fast food and soft drinks, but two different trials were added – two types of sweets (M&Ms and Jelly Belly) and two cereals (Froot Loops and Fruity Pebbles).
They again looked at the associations with age and gender-specific BMI.
What were the basic results?
In study one, most participants (60%) were of a normal weight. The average child brand knowledge score across the four food groups was 13.
Brand knowledge was significantly associated with BMI. As brand knowledge increased, so did BMI. Brand knowledge was said to account for 8.4% of the variance in BMI scores. There was no link between TV viewing and BMI; however, there was a significant link between physical activity and BMI. As physical activity increased, BMI decreased. Physical activity was said to account for an even greater proportion of variation in BMI scores than brand knowledge – 63.2%.
In fact, when the model took brand knowledge, TV viewing and physical activity into account, the association between brand knowledge and BMI was no longer statistically significant.
When looking at associations with being overweight/obese, increased physical activity significantly decreased the risk (by 58%) that the child would be. TV viewing and brand knowledge were not significantly associated with being overweight/obese.
The average brand knowledge score for this sample was also 13, and most of the sample (68%) were of a normal weight. Replicating the findings of study one, TV viewing was not significantly associated with BMI, but brand knowledge was – this time accounting for a 16.5% of the variance in BMI scores.
However, this time, there was no significant association with physical activity. This study replicated the findings for brand knowledge, but not for physical activity. In this study, increased brand knowledge significantly increased the risk of a person being overweight or obese (by about a third).
How did the researchers interpret the results?
The researchers conclude that across the two studies, a child’s brand knowledge significantly predicted their BMI, even when adjusting for age, gender and extent of TV viewing.
They comment on “the success of physical activity to counter the influence of brand knowledge on BMI in the first study". However, they then say that "the failure to replicate this finding in the second study suggested that exercise was not a robust predictor of child BMI”.
This research includes two small studies of young children, with the aim of assessing their knowledge of brands high in fat, salt and sugar, as well as their TV viewing and physical activity levels. They then looked at how these factors were linked to their BMI.
In both samples, increased brand knowledge was significantly associated with increased BMI, though the second study found a stronger association with brand knowledge.
Interestingly though, the first study found that physical activity had a much greater effect on BMI, and mitigated all of the effects of brand knowledge.
In short, brand knowledge was predicative of BMI, but this effect was removed if the child engaged in frequent physical activity.
The second study did not find a link with physical activity; the researchers have said this supports previous study findings that physical activity may not be sufficient to reduce BMI in children.
However, concluding on the limited role of physical activity in reducing BMI seems a fairly strong conclusion to make based on this very small study, which has numerous limitations:
- It is plausible that a child’s increased knowledge of foods and drinks that contain high levels of fat, salt and sugar may be associated with their higher consumption, as well as increased BMI. However, this study is only cross-sectional, so can only demonstrate associations. It cannot prove that the child’s brand knowledge is directly linked to their current BMI.
- The study includes only two separate groups of children. The majority of children in each group were of a normal weight. Therefore, examining associations between the responses in the small proportion of children overweight or obese BMIs decreases the reliability of any associations found.
- All measures on child physical activity and TV viewing were through parental self-reporting, which opens up the possibility of inaccurate estimations.
- The child was only asked to perform a task assessing their knowledge of different and competing fast food, soft drink, cereal, sweet and crisp brands. It gives no indication how often and in what quantity they may or may not eat these particular foods. We also don't know anything about the children’s food and drink intake.
- As said, these are only two very small groups of US children, aged three to five years. The samples did benefit from a broad ethnic mix; nevertheless, larger samples of children of different ages and from different geographical regions could provide different results.
Understanding the influences and patterns on child consumption patterns may help develop measures to target the growing obesity epidemic, and its associated health problems. However, this single small study answers few questions on its own. The study will contribute to the wider literature on overweight and obese children, and its influences, which considered as a whole may help to find new angles for intervention.
It is most likely that a child’s BMI is going to be influenced by a combination of both their diet and their physical activity levels.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.