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Dietary Restraint Could Offset Effects of Obesity Risk Genes

Practising dietary restraint could significantly reduce the effects of obesity risk genes, according to new research led by the University of Exeter. 

The authors said their study was the first to show that cognitive restriction of eating could reduce the association between genetic risk of obesity and increased body mass index (BMI) as indirectly mediated by eating behaviours.

They explained that the rising prevalence of obesity has been attributed both to an obesogenic environment and to individual genetic variation. Genetic variation is believed to explain 40% to 70% of differences in BMI, and genome-wide association studies have identified over 900 single nucleotide variants associated with individual weight. Whilst individually these account for a small proportion of interindividual BMI variance, in aggregate they can be used to formulate a single score to assess a person's susceptibility to obesity.

Up to a quarter of the effect of obesity risk genes in increasing BMI may be explained by increases in hunger and loss of control towards food, including emotional eating, the team said. 

Lead author Shahina Begum, a psychology doctoral candidate at the University of Exeter, said, "At a time when high calorie foods are aggressively marketed to us, it's more important than ever to understand how genes influence BMI."

Single Score to Assess Genetic Risk of Obesity

For their study, published online July 6 in the International Journal of Epidemiology, the researchers assessed nearly 4000 individuals enrolled in two existing UK cohort studies, 2101 people in the EXETER 10,000 Genetics of Appetite sub-study (GATE) and 1679 adult offspring from the Avon Longitudinal Study of Parents and Children (ALSPAC).

The study participants, aged between 22 and 92, had their weight and height measured and provided blood sample for a DNA analysis, from which the team calculated an overall score for their genetic risk of obesity. Participants also completed questionnaires to measure 13 different eating behaviours, including disinhibition (a tendency to engage in binge or emotional eating) and over-eating due to hunger.

As expected, the researchers found that a higher genetic risk score was associated with a higher BMI, and that this was partly due to uncontrolled eating dependent on various eating behaviours, specifically:

  • Increased disinhibition in response to habitual and situational cues
  • Emotional disinhibition
  • Emotional over- and under-eating
  • Hunger in response to internal and external triggers

'Daily Overeating Opportunities' in Western Obesogenic Environment 

The stongest mediation of the influence of genetic risk score on BMI was habitual disinhibition, at 18%. The researchers said: "This may be the most frequent pathway in which BMI-genetic mechanisms are realised, because it measures tendency to overeat in response to daily life circumstances, and there is a high level of daily overeating opportunities within the Western obesogenic environment."

Their results also sbowed that participants who had high levels of dietary restraint reduced those effects by almost half for disinhibition and by a third for hunger – "suggesting that restraint may counteract some of the effects of genetic risk", they said. 

Both flexible restraint strategies, such as being conscious about what is eaten and deliberately taking small servings, and rigid strategies, like calorie counting, moderated the genetic predisposition to increased BMI. However this was not directly, but via their indirect effects on the pathway mediated by disinhibited eating and external hunger.

Restraint Strategies Could Counteract Uncontrolled Eating

Obesity risk genes make people feel hungrier and lose control over their eating, but practicing dietary restraint could counteract this and potentially improve BMI in people genetically at risk, the team concluded.

"We already know that these genes impact traits and behaviours such as hunger and emotional eating, but what makes this study different is that we tested the influence of two types of dietary restraint — rigid and flexible — on the effect of these behaviours", Begum said. 

"What we discovered for the first time was that increasing both types of restraint could potentially improve BMI in people genetically at risk; meaning that restraint-based interventions could be useful to target the problem."

The team suggested that interventions to facilitate dietary restraint could include changing the food environment, such as reducing the calorie content or portion size of food, or supporting individuals to develop strategies to make healthier food choices. 

To the latter end, members of the research team have developed a food trainer app, FoodT, a brain training game that retrains the brain's automatic responses to high calorie foods, making it easier for people to resist temptation and meet their own dietary goals. Research suggested this training may be particularly beneficial for those with a higher BMI, they said. The app is available for Android and iPhone, or the game can be played online.

The work was supported in part by a grant from the Great Western 4 Biomed Medical Research Council (MRC) Doctoral Training Partnership, awarded to the Universities of Bath, Bristol, Cardiff and Exeter from the MRC/UK Research and Innovation. The authors have disclosed no relevant financial relationships.

Intl J Epidemiol. Published online July 6, 2023. Full text