This is nonsense. Children aren’t tiny adults their bodies repair and heal better BUT they are enormously affected by diet because their physiological stage is entirely different from adulthood - it’s a stage of enormous energy requirement as well as maturation of immune systems, organs, lean mass, growth, brain development etc.
The most common form of malnutrition in the UK is micronutrient deficiencies - you can have obesity and be malnourished at the same time (double burden) by eating an unhealthy diet too high in calories, fats, sugar and salt and not high in Mns. Micronutrient deficiencies can lead to long and short term issues .
In the short term, it often shows up as tiredness, irritability, trouble concentrating, digestive issues, and more frequent infections because their immune systems rely heavily on steady nutrient intake.
Children have small stomachs and high nutritional needs, so even a few days of low‑quality food can noticeably affect their energy and behaviour.
Over months and years, consistently poor nutrition can lead to more serious conditions. These include obesity, type 2 diabetes, high blood pressure, iron‑deficiency anaemia, vitamin D deficiency, and weakened bones. Growth can slow or falter, and learning can be affected because the developing brain is extremely sensitive to nutrient shortages. Emotional wellbeing can also suffer, with links to low mood and anxiety.
The risk is higher in childhood not lower - because this is a period of rapid growth, brain development, and immune maturation.