Published August 3, 2021 at 11:32 AM
Domestic. A gene variant that was previously linked to an increased risk of overweight and obesity may, according to a new study from Uppsala University, instead reduce the risk of obesity in adolescence if the carrier is breastfed for a long time.
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The results of the study, published in Obesity Science & amp; Practice suggests that “risk genes” can be beneficial if the individual is given the right conditions.
– We have looked at both a specific gene and obesity in young people and investigated whether there are environmental factors that affect the connection. What distinguishes our study from many previous studies is that we not only looked at risks but also at a positive factor, in this case breastfeeding, says Sofia Kanders, doctoral student at the Department of Neuroscience at Uppsala University and the study's first author.
Genes are made up of nucleotides that exist in four different variants: A, T, C and G. How and where the nucleotides are located in the gene is determined by our heritage. In this case, the researchers have investigated variants of the FTO gene where the combinations AA, AT or TT are possible at a certain place in the gene.
Previous research has found that the more A's found on this specific position in the gene the greater the risk of developing obesity. But what role do environmental factors play? To test this, the researchers chose to look at breastfeeding that has a known positive effect on the baby's early growth.
A thousand young people had to fill in a questionnaire on three different occasions: 2012 when they were on average 14 years old, 2015 when the average age was 17 years and 2018 when they were on average 20 years old. Saliva samples determined which of the three FTO variants they had. At the same time, their mothers had to answer questions about how long the children were breastfed: from no breastfeeding at all to more than two years.
As other studies have previously shown, a clear connection was also seen here between a short breastfeeding period and an increased incidence of higher BMI (body mass index) in adolescents with the FTO variant AA compared with AT or TT.
But a completely different patterns emerged at the second question point when the researchers looked at the young people who had been breastfed for a long time: 19.9 months or more. The group with the AA variant then showed a significantly lower incidence of obesity. Even when the degree of physical activity was taken into account, the connection remained. At the last question, when the young people got older, however, that pattern could no longer be seen, which is considered to be due to the fact that many other environmental factors then affect body weight.
The researchers believe that the results support the theory that certain people are genetic sensitive to obesity and that external factors can therefore have a greater impact in both a positive and negative way.
– The most important conclusion is that the results suggest that AA may be a plasticity variant, ie a sensitivity variant, which is not only a risk variant but can also give a positive outcome depending on what the environment looks like, but more research is needed here, says Sofia Kanders in a mailing.