Children with acute lymphoblastic leukaemia (ALL) are at risk of metabolic and cardiovascular complications. We evaluated the development of overweight and obesity for 5 years after diagnosis in children and adolescents treated for ALL.

The medical records of children diagnosed with ALL at one centre during 2000–2018 were assessed. Weight and height measurements were retrieved from medical records and were used to calculate age- and sex-adjusted International Obesity Task Force-Body Mass Index (ISO-BMI). ISO-BMI was determined at selected time points during treatment and up to 5 years after diagnosis, and the change in mean ISO-BMI was assessed.

We studied 115 patients diagnosed with ALL, 54 (47%) of whom were male. Mean age at diagnosis was 6.6 ± 4.6 (range 0–17.99) years. ISO-BMI increased significantly during treatment (p < 0.0001) and remained elevated at 5 years after diagnosis (p < 0.0001). The number of overweight and obese patients increased from 17% and 4% at diagnosis to 26% and 16% at the five-year follow-up.

Patients treated for ALL are at significant risk of weight gain and obesity, with the prevalence of overweight and obesity doubling from diagnosis to 5 years post-treatment. ISO-BMI remained persistently elevated across all treatment risk groups.

• Children and adolescents with acute lymphoblastic leukaemia (ALL) are at risk of metabolic and cardiovascular late effects.
• The number of overweight and obese subjects doubled from ALL diagnosis to five-year follow-up, with over 40% of children and adolescents being overweight or obese at 5 years after diagnosis.
• Excess weight gain during ALL treatment affected all the treatment risk groups, so effective ways to intervene are needed.