Snacking, as well as unhealthy and emotional eating, share a common genetic risk with measures of obesity, namely body mass index (BMI) and waist circumference, a study of twins suggests.
The findings indicate that genetic susceptibility to obesity may be influenced by frequent snacking.
The study, “The genetic architecture of the association between eating behaviors and obesity: combining genetic twin modeling and polygenic risk scores,” the study was published in The American Journal of Clinical Nutrition.
The factors that influence obesity risk are complex, involving an interplay of environmental factors, lifestyle, and genetics. As such, eating habits and the type of diet can influence the genetic susceptibility for obesity.
Previous studies in twins have shown that genetics explain roughly 57–90% of the variability in BMI in adults and 40–60% of the variance in eating habits. Some studies suggest that genetic factors also could guide the association between BMI and eating behavior traits, including uncontrolled eating, and emotional eating.
Genes linked to the susceptibility for obesity are highly active in the central nervous system (brain and spinal cord), with their activity likely to influence appetite and satiety (feeling “full”).
In this study, researchers at the University of Helsinki, in Finland, set out to better understand whether genetic risk for obesity is linked to specific eating behaviors.
In a nationwide approach, they studied 3,977 individual twins (33% identical twins, 56% women), ages 31 to 37) from the FinnTwin16 (FT16) group, which includes data on Finnish twins born from 1975 to 1979.
Participants had an average BMI of 24.8 and a mean waist circumference (WC) of 86.1 centimeters (cm), two standard measures for assessing obesity. Diet was evaluated using the Diet quality score (DQS) that ranges from 0 to 12, with higher scores indicating a better diet. In this group, the mean DQS was 7.
Women had lower BMI and WC than men, but had abdominal obesity more often. Women also had a higher quality diet.
Eating behaviors were evaluated via a questionnaire on eating styles and DQS. Researchers identified four patterns: snacking; infrequent or unhealthy eating; avoidant eating; and emotional and external eating. Overall, that explained about 56% of eating styles and diet quality variance.
Notably, avoidant, or health-conscious eating included avoiding greasy meals and calories. External eating refers to eating in response to external cues, such as sight or smell of food.
The researchers then assessed the heritability of eating behaviors and obesity. Their approach assumed that identical twins share virtually the same genetic sequences, while fraternal twins and other siblings share 50%.
Results indicated that eating behaviors had a moderate heritability, ranging from 36% to 48%. As the team expected, the heritability for BMI (76%) and waist circumference (62%) were high.
Both BMI and waist measures correlated with snacking and emotional/external eating.
For these two eating traits, genetic correlations with obesity were stronger than environmental links. Genetics explained 71–75% of the correlation between snacking and the two obesity measures, and 64–75% of the link between emotional/external eating and both BMI and waist circumference.
The team then used data from 1,055 twins to create a polygenic risk score for BMI (PRS-BMI), which incorporated information from almost 1 million single nucleotide polymorphisms — mutations in a single building block of DNA.
The findings showed that only snacking and infrequent/unhealthy eating influenced the association between PRS and the two obesity measures in a significant manner. In contrast, emotional and external eating only influenced the link between PRS and BMI.
Also, PRS-BMI was positively associated with snacking, meaning that participants with a higher score were more prone to snacking. Also, greater likelihood to snacking correlated with higher BMI and larger WC.
Overall, the results suggest that “genetic susceptibility to obesity can be partly mediated by an eating pattern characterized by frequent snacking” the researchers wrote.
“Obesity prevention efforts might therefore benefit from focusing on eating behavior change, particularly in genetically susceptible individuals,” they concluded.
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