Paediatric obesity is a disease with multisystem complications, which drives referrals to subspecialist clinics in all areas of paediatrics
International data from the World Health Organisation (WHO) highlights the frightening trend in obesity in children over the last few decades – with 8 per cent of children and adolescents aged five to 19 years old now living with obesity (equating to 160 million young people), compared to just 2 per cent of children and adolescents worldwide with obesity in 1990 (31 million young people). This is in addition to the 20 per cent of children who are classified as overweight worldwide in 2022 compared with 8 per cent of children in 1990.1
Defining obesity as a disease
Obesity is generally defined as abnormal or excessive fat accumulations which presents a risk to health. It was first included in the International Classification of Diseases as far back as 1948, and yet adolescents with the disease of obesity can still face stigma today when attending healthcare appointments, mainly due to a misconception that it is a cosmetic issue caused by over-eating and lack of impulse control.
Following a steady trend of increasing incidence of obesity internationally, many health authorities have further emphasised obesity as a disease. In 2013, the American Medical Association classified obesity as a “chronic, relapsing, multifactorial, neurobehavioral disease wherein an increase in body fat promotes adipose tissue dysfunction…. Resulting in adverse metabolic, biomechanical and psychosocial health consequences”.2 The European Commission equally identified obesity as a chronic disease in 2021, describing it as a “chronic relapsing disease, which in turn acts as a gateway to a range of other non-communicable diseases, such as diabetes, cardiovascular disease, and cancer”.2 Recognition of obesity as a disease is crucial as it allows strategies to be put in place for prevention, identification, early intervention, and treatment to improve patient health, quality-of-life and overall mortality, whilst reducing healthcare costs.
Childhood obesity in Ireland
Obesity among Irish children mirrors this international trend. The Irish Childhood Obesity Surveillance Initiative (COSI) is an ongoing, systematic process of data collection, analysis, and reporting on childhood obesity in primary school children in collaboration with WHO Europe. The most recent report from 2022–2023 estimates that in primary school, 17.7 per cent of children are living with overweight or obesity.3 Children attending schools classified as more disadvantaged have significantly higher rates of obesity compared to their more affluent counterparts.
Similar adolescent data from the ‘Growing up in Ireland study’ confirms this trend, with 24 per cent of adolescents living with overweight/obesity in 2020, compared with 18 per cent in 2006, and 13 per cent in 1990.4 Within this adolescent cohort, there was a substantial increase in both the amount and the severity of obesity. In 2020, 8 per cent of adolescents had obesity, compared with 3 per cent in 2006, and 0.5 per cent in 1990 (p<0.001).4
Paediatric obesity is a disease with multisystem complications which drives referrals to subspecialist clinics in all areas of paediatrics. For example, a child with obesity may require respiratory consultation for obstructive sleep apnoea, endocrinology input for insulin resistance or type 2 diabetes, nephrology for hypertension, neurology for intracranial hypertension, orthopaedics for slipped upper femoral epiphysis or Blount’s disease, gastrointestinal input for hepatic steatosis, and dermatology input for hidradenitis suppurativa, to name but a few. The psychological burden of the disease of obesity is significant, with adolescents reporting low self-esteem, bullying, marginalisation, and high rates of school absenteeism. Paediatric obesity is a strong predictor of lifelong adverse health outcomes, with increased rates of cardiovascular disease, hypertension, and type 2 diabetes leading to decreased life expectancy.5
Many parents and health practitioners alike have preconceptions that childhood obesity is transient and that most children grow out of this as they progress through adulthood, with statements such as ‘puppy fat’ or ‘waiting for a growth spurt’ frequently heard. Research suggests that this is not the case for children and adolescents living with obesity. Half of all children over six years old with obesity will have obesity in adulthood. This figure increases further for adolescents with obesity to 80 per cent, and with it, all the secondary non-communicable complications of obesity.6
Aetiology
Obesity is a chronic disease, which is caused by a complex interplay of genetic, psycho-social, and lifestyle factors, impacted hugely today by the obesogenic environment in which we live. ‘Set-point theory’ suggests that humans have a predetermined weight range, which is regulated by neuroendocrine physiological mechanisms. Once this ‘range’ is upregulated by biopsychosocial events, including stressful life events and living in an obesogenic environment, it becomes hugely challenging to downregulate this set point again.7 Upon successful weight loss, the body triggers adaptive responses such as modulation of satiety hormones, altered food preferences through behavioural change, and reduction in metabolism. New pharmacological therapies aim to target some of the hormonal receptors which influence satiety and fullness.
Management in the Irish context
The Irish framework for management of child and adolescent obesity is guided by the HSE Model of Care for the Management of Overweight and Obesity.8 Effective obesity treatment involves a multidisciplinary team (MDT) approach with a focus on parental education and familial behavioural change. First-line treatment is lifestyle intervention with nutritional support, physical activity, and behavioural therapy.
An audit of the MDT-guided ‘W82GO’ programme at Children’s Health Ireland (CHI) showed a reduction in body mass index standard deviation scores (BMI-SDS) in almost two-thirds of children attending the lifestyle advice programme over a 12-year period. This shows that most children living with overweight or obesity can be managed at primary and secondary level, although an increase in health and social care professions (HSCP) support at local community level is crucially required to meet the national demand. Children with ‘complex obesity’ (BMI >99.6th centile with two or more obesity-related complications) meet criteria for referral to CHI’s tertiary complex obesity service, established in 2023.
Pharmacological therapies are relatively novel in paediatric obesity, but are being used with increasing frequency worldwide. Glucagon-like peptide-1 (GLP-1) agonists have shifted the paradigm for obesity treatment as they permit the opportunity to treat the disease of obesity itself, rather than reactively treating its complications. GLP-1 receptor agonists – liraglutide (max 3mg) daily subcutaneous injection and semaglutide (max 2.4mg) weekly injection were licenced and approved by the European Medicines Agency for use in adolescents 12 years and older in 2018 and 2023, respectively. These medications are commenced at low doses and titrated gradually to full doses as tolerated. They act by regulating hunger via central nervous system effects and delayed gastric emptying, and improve metabolic parameters by increasing insulin secretion and reducing insulin resistance.9 In addition to this, there is some evidence that GLP-1 agonists regulate reward pathways involved in eating behaviours, and may reduce impulsivity and binge eating patterns.10
Evidence for GLP-1 receptor agonist efficacy in the paediatric population is scarce compared to the adult population. For liraglutide, the SCALE Teen randomised-controlled trial (RCT) demonstrated a statistically-significant reduction in BMI in adolescents on liraglutide over a 56-week treatment period compared with placebo – a BMI reduction of 10 per cent or more occurred in 26.1 per cent of participants when combined with intensive lifestyle intervention alone.11 However, once liraglutide was stopped, adolescents in the trial rebounded back to their original BMI.
Semaglutide has shown a higher level of weight reduction compared to liraglutide, whilst its administration as a weekly injection compared to a daily injection makes it more tolerable to adolescents, thus promoting compliance. The STEP TEENS clinical trial at week 68 showed average body weight loss of 14.7 per cent among adolescents on the medication, with >10 per cent body weight loss in 61.8 per cent of users, and >15 per cent body weight loss in 53.4 per cent of users.12 This medication was generally well tolerated in both RCTs, with transient gastrointestinal disturbance the most commonly reported side-effect. There is an increased risk of pancreatitis and gallstones compared to placebo, whilst this medication is contraindicated if there is a family history of medullary thyroid hyperplasia and in pregnancy.
When extrapolating the data from these trials for use in a clinical context, it is important to note that the patient group selected in both trials had a stabilised weight trajectory for three months prior to starting medication. Each patient also underwent intensive lifestyle advice focusing on nutrition and activity for a 12-week run-in period prior to starting anti-obesity injectable medication. This emphasises the importance of using GLP-1s as an adjunct to HSCP supports, rather than using medication as an alternative in isolation.
Further questions remain to be answered when using GLP-1 agonists for obesity management. There is limited evidence for efficacy of GLP-1s in children under 12 years at present, but small safety studies show promising weight stabilisation effects.13 No long-term data is available yet for young people on GLP-1 agonists, and as mentioned, weight gain tends to rebound upon cessation. This raises the question, will a paediatric patient commenced on GLP-1 agonists require them for life? Could micro-dosing of GLP-1s be effective in maintaining BMI control, once weight-loss has been achieved? When will GLP-1 agents be available orally (studies ongoing), and will they have the same weight-loss benefit as their injectable counterparts?
Looking to the future for Irish young people
In Ireland, GLP-1 receptor agonists are not reimbursed for treatment of obesity in children and adolescents. This places the responsibility on parents to self-fund this medication, which costs around €150–€200 per month. Given the higher prevalence of the disease of obesity in socially disadvantaged areas, this expense is prohibitive to most families. This has the potential to further widen the gap in obesity distribution between social classes.
Even for those families that can afford medication in the short-term, GLP-1 agonists are not a short-term therapy option. Petition to Government agencies for funding for these agents as part of a wider national weight management strategy is ongoing. Irish adults have access to liraglutide through the HSE managed access protocol if they meet criteria: ≥35kg/m2 with prediabetes and high risk of cardiovascular disease, and have an effective response to medication after 12 weeks.14 Through this managed access protocol, the medication is funded and can be accessed outside of specialised tertiary obesity services. There is a need for Irish adolescents to be included in all future programme planning, including access to anti-obesity medication, to provide early intervention in order to reduce the risk of future complications, which will inevitably occur when obesity follows most of these young people into adulthood.
In line with international standards, there are plans for paediatric bariatric surgery as part of the HSE Model of Care for the Management of Overweight and Obesity 2025.8 This will be one national centre for a select group of young people, located within the new National Children’s Hospital, consisting of a consultant-led MDT for complex case management, assessment, and approval for bariatric surgery and comprehensive pre-, peri-, and post-operative education and support. Internationally, paediatric bariatric surgical options focus on laparoscopic sleeve gastrectomy and Roux-en-Y gastric bypass surgery.15,16 Exact criteria will be further outlined in national guidelines upon their completion and publication.
Resources for practitioners
For Irish healthcare professionals wanting to access educational resources or resources to provide families under their care, there is a wealth of information available on www.childhoodobesity.ie – the national paediatric obesity management website developed by Sláintecare and the RCSI. This includes a series of e-learning modules with continuing professional development accreditation for healthcare professionals on childhood obesity, leaflets for parents, and links to international guidelines. Additional resources available include the ‘Making every contact count’ e-learning module for paediatric and adult practitioners on HSELand, and the Healthy living with CHI booklet, available on the CHI website, www.childrenshealthireland.ie
References
1. World Health Organisation. Obesity and overweight [Internet]. Geneva: WHO; 2025. Available at: www.who.int/news-room/fact-sheets/detail/obesity-and-overweight [cited 2025 Oct 14]
2. Burki T. European Commission classifies obesity as a chronic disease. Lancet Diabetes Endocrinol. 2021;9(7):418
3. Kilduff O, Slattery J, Lee C, O’Brien S, et al. The Childhood Obesity Surveillance Initiative (COSI) in the Republic of Ireland – Findings from 2022 and 2023. Dublin; 2024
4. Layte R, McCrory C. Growing Up in Ireland: Key findings from the longitudinal study of children. Dublin; 2018. Available at: www.growingup.gov.ie/growing-up-in-ireland-publications/
5. Rubino F, Cummings DE, Eckel RH, Cohen R V, et al. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes Endocrinol. 2025;13(3):221-262
6. Simmonds M, Llewellyn A, Owen CG, Woolacott N. Predicting adult obesity from childhood obesity: A systematic review and meta-analysis. Obes Rev. 2016;17(2):95-107
7. Ganipisetti VM, Bollimunta P. Obesity and Set-Point Theory. [Updated 2023 Apr 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan. Available at: www.ncbi.nlm.nih.gov/books/NBK592402/
8. Health Service Executive. National Clinical Programme for Obesity [Internet]. Model of Care for the Management of Overweight and Obesity. 2020. Available at: www.hse.ie/eng/about/who/cspd/ncps/obesity/model-of-care/
9. Agosta M, Sofia M, Pezzino S, D’Amato S, et al. Efficacy of liraglutide in paediatric obesity: A review of clinical trial data. Obes Med. 2024;48:100545
10. Bartkoski M, Poweleit EA, Stancil SL. GLP-1 Agonists for paediatric psychopharmacology: Opportunities and cautions. Clin Transl Sci. 2025;18(6):e70262
11. Kelly AS, Auerbach P, Barrientos-Perez M, Gies I, et al. A randomised controlled trial of liraglutide for adolescents with obesity. N Engl J Med. 2020;382(22):2117-2128
12. Weghuber D, Barrett T, Barrientos-Pérez M, Gies I, et al. Once-weekly semaglutide in adolescents with obesity. N Engl J Med. 2022;387(24):2245-2257
13. Mastrandrea LD, Witten L, Carlsson Petri KC, et al. Liraglutide effects in a paediatric (7–11 years) population with obesity: A randomised, double-blind, placebo-controlled, short-term trial to assess safety, tolerability, pharmacokinetics, and pharmacodynamics. Paediatr Obes. 2019;14(5):e12495
14. Health Service Executive. Liraglutide (Saxenda) [Internet]. Available at: www.hse.ie/eng/about/who/cspd/medicines-management/managed-access-protocols/liraglutide-saxenda-/ [cited 2025 Oct 16]
15. Hampl SE, Hassink SG, Skinner AC, et al. Clinical practice guideline for the evaluation and treatment of children and adolescents with obesity. Paediatrics. 2023;151(2):e2022060640
16. National Institute for Health and Care Excellence. Overview | Overweight and obesity management | Guidance | NICE. 2025 Jan 14 [cited 2025 Oct 14]; Available at: https://www.nice.org.uk/guidance/ng246
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