A heartier appetite is linked to more rapid infant growth and to genetic predisposition to obesity, according to two studies recently published by our researchers in the journal JAMA Pediatrics.
Although it is clear that some people seem to struggle much more than others to keep a healthy weight, so far it has been less obvious why this is the case. Researchers from our department have now shown that differences in appetite, and especially lower satiety sensitivity (a reduced urge to eat in response to internal ‘fullness’ signals) and higher food responsiveness (an increased urge to eat in response to the sight or smell of nice food) may hold the key to unhealthy weight gain.
In the first study, the researchers showed that infants with a heartier appetite grew more rapidly up to age 15 months, potentially putting them at increased risk of obesity.
Our researchers used data from non-identical, same-sex twins born in the UK in 2007. As we have previously discussed, twins are a good model to study differences between people because they are born at the same time, and usually grow up in a very similar environment.
Twin pairs were selected that differed in measures of satiety responsiveness (172 pairs) and food responsiveness (121 pairs) at 3 months, and their growth up to age 15 months was compared. Within pairs, the infant who was more food responsive or less satiety responsive grew faster than their co-twin.
The more food responsive twin was 654g heavier (1.4lbs) than their co-twin at six months and 991g heavier (2.1lbs) at 15 months. The less satiety responsive twin was 637g heavier (1.4lbs) than their co-twin at six months and 918g heavier (2lbs) at 15 months.
This is a considerable weight difference for children of this age, and represents a 10% weight difference. Over time as weight differences increase, these children are at a higher risk of obesity. Therefore, it might be beneficial to watch out if a child seems to have difficulties filling up, or seems to be somewhat responsive to food cues in the environment.
However, this first study could not tell whether children with low satiety responsiveness or high food responsiveness would continue to be heavier; nor did it tell about possible underlying genetics.
Therefore, the second study was set up to shed more light on how appetite, and especially low satiety responsiveness, acts as one of the mechanisms underlying genetic predisposition to obesity. For this study, our researchers collaborated with a team from King’s College, London.
The researchers accessed data from over 2,000 unrelated 10-year-old children born in the UK between 1994 and 1996. First, the team created a combined genetic risk score (polygenic risk score) for each child. To do this, they added up the number of higher risk versions of 28 obesity-related genes (each gene has 2 versions, as we all get one version from Mum and one version from Dad). A higher polygenic risk score meant that the child was at higher genetic risk of obesity.
The researchers then looked at how the children’s genetic risk scores related not only to their satiety responsiveness, but also to their body fatness (measured using body mass index and waist circumference).
As expected, they found that children at a higher genetic risk of obesity had higher BMIs (which is a measure of weight status) and a larger waist circumference. This finding was in line with what we already know about the genetic basis of obesity (see our other blogpost). But key to our study was showing that they were also less sensitive to satiety.
This finding suggests that satiety responsiveness is one of the mechanisms through which ‘obesity genes’ influence body weight. Therefore, it might indeed be beneficial to teach children with lower satiety sensitivity techniques that might improve their fullness signals when eating. Advice to parents on encouraging children to eat more slowly, having a ‘no second helpings’ policy, and keeping tempting treats out of sight between meals could help. Knowing that there are genetic influences on appetite might help parents understand and accept that children differ, and that some need more support in learning the boundaries of appropriate eating.
Likewise, for adults who feel they have difficulty controlling their weight, it might be beneficial to understand that differences in appetite might be one contributing reason. Techniques that help adults to ‘feel’ the fullness, such as ‘mindful eating’ and portion control may be useful aides in ‘outsmarting’ any biological tendencies to eat too much.
Article references: JAMA Pediatrics
van Jaarsveld CM, Boniface D, Llewellyn CH, Wardle J. Appetite and Growth: A Longitudinal Sibling Analysis. JAMA Pediatr. 2014;():. doi:10.1001/jamapediatrics.2013.4951.