Understanding The Role Of Appetite In The Development Of Eating Disorders

Principal investigator: Dr Clare Llewellyn

Location: UK

Funding Period: 2018-2022

How does appetite and a parents’ approach to feeding impact the development of eating disorders?

The project

Eating disorders like anorexia nervosa, bulimia nervosa and binge-eating disorder are serious mental illnesses with life-limiting impacts. Anorexia has the highest mortality rate of any mental illness. And these conditions are a huge public health problem costing the UK around £15 billion a year.

Eating disorders often arise before age 18 and around a quarter of young people report having some symptoms. However, we have limited understanding about how they emerge, so prevention is impossible and treatments often take years to have impact.

Research into these conditions has previously focused on psychological risk factors, like image and self-esteem, while behavioural and biological factors have been largely ignored. Potential advances in how we protect and treat those at risk could be being missed.

Dr Clare Llewellyn and her team at UCL are looking at two factors in childhood that may be crucial in understanding the development of eating disorders – appetite and parental feeding strategies.

The process

Clare’s previous work has focused on obesity. Eating disorders and obesity are both problems related to food intake and are heritable, suggesting some similarities.

Her studies showed that a child’s appetite is influenced by both their genetics and their parents’ approach to feeding them, impacting weight gain and a child’s risk of obesity.

This research set out to investigate how appetite traits in early childhood and parental feeding practices influence the risk of developing eating disorder (ED) symptoms in adolescence. The project was motivated by the need for better prevention and early intervention strategies for different eating disorders, which are difficult to treat once established.

To find out, Clare analysed data from twins, where mental health, genetic and parental factors have been tracked from birth through to teenage years. This will allow her to see how appetite and parents’ feeding practices impact on eating habits in adolescence. This could allow us to predict who may be at risk of developing behaviours associated with eating disorders.

The outcome

Key findings include:

Children who were more ‘food responsive’—those with a strong urge to eat when tasty food was available—had a higher risk of a broad range of eating disorder symptoms in adolescence, especially binge eating. This trait was identified as a neurobehavioural risk factor for both obesity and eating disorders;
Children who were more sensitive to fullness and ate more slowly were at lower risk of some ED symptoms;
Parental feeding practices had a small and inconsistent effect on later ED symptoms, with responsive feeding practices showing a slight protective effect;
Genetic analyses revealed that appetite and ED symptoms share some genetic architecture, and that environmental influences unique to each child play a significant role;
Food fussiness was found to be a stable trait from toddlerhood to adolescence, with strong genetic influence;
Emotional overeating was shaped mainly by shared environmental factors in early life, with genetic effects emerging in adolescence;
The transition to university was identified as a vulnerable period for increases in ED symptoms;

Papers published:

Llewelyn et al, 2023 : Behavioural susceptibility theory: the role of appetite in genetic susceptibility to obesity in early life. The Royal Society.
Nas, Llewelyn, Herle et al, 2024: Nature and nurture in fussy eating from toddlerhood to early adolescence: findings from the Gemini twin cohort. PsyArXiv PrePrints.
Treasure, Nas, Llewelyn et al, 2024: Early childhood appetitive traits and eating disorder symptoms in adolescence: a 10-year longitudinal follow-up study in the Netherlands and the UK. The Lancet.

The impact

Scientific and societal impact:

The research has highlighted appetite traits in early childhood as a potential marker for vulnerability to both obesity and eating disorders, opening new possibilities for early identification and intervention;
It suggests that behavioural and pharmacological interventions targeting appetite (such as GLP-1 receptor agonists) could support treatment for eating disorders, especially binge eating;
The findings support current advice for responsive feeding and may help alleviate parental guilt regarding children’s eating difficulties, as parental feeding practices were not found to be a major risk factor;
The project has led to further funding, new collaborations, and ongoing research, with the potential to influence public health policy and clinical guidelines;
Patient and public involvement was integral, ensuring that research outputs were framed appropriately and sensitively for those affected by eating disorders;
The work has contributed to the development of new interventions and public health strategies, and has been recognised through awards, grants, and public engagement activities.

Dr Clare Llewellyn

Dr Clare Llewellyn is a lecturer in the Department of Behavioural Science and Health at UCL. Clare’s research interest is to understand how genes and the environment impact eating habits.

Supported by the MQ Rosetrees Fellowship. The MQ Rosetrees Fellowship has been fully funded thanks to the generosity of The Rosetrees Trust. MQ would like to express our appreciation to them for their critical support.