According to paediatric dietitian Kath Megaw, the key clinical question is not simply what does this child eat?, but what has changed? A child may start preschool, experience repeated infections, enter a growth spurt, become more active, develop food allergies or sensory challenges, or begin restricting their diet. Each can alter the balance between nutritional intake and physiological demand.

Look beyond the snapshot

A 24-hour dietary recall can provide useful information, but it should not be interpreted in isolation. McGaw recommends considering five elements together: Growth, dietary intake, appetite and feeding, health, and life context.

Growth should be assessed through serial measurements of weight, height or length, body mass index or weight-for-length, with particular attention to the trajectory. A child does not necessarily need to be underweight before concern is warranted. A change in growth velocity or downward movement away from an established trajectory may be an earlier warning sign.

Dietary assessment should go beyond the foods consumed to consider quantity, frequency, variety, drinks and supplements. Appetite, meal duration, food refusal and sensory issues may reveal why intake is inadequate. Recurrent illness, gastrointestinal symptoms, medication and chronic disease can alter nutritional requirements, while school, sport, family routines, stress and access to food can all influence what a child is realistically able to eat.

When illness changes the nutritional equation

Illness can create a double nutritional burden. Intake may fall because of poor appetite, sore throat, nausea, vomiting, diarrhoea or altered taste and smell, while fever, inflammation, gastrointestinal losses and tissue repair during recovery can increase nutritional stress.

For a well-nourished child, a single short illness may have little lasting effect. Repeated illnesses, however, can create cumulative nutritional deficits, particularly when appetite and weight have not fully recovered before the next infection occurs.

Importantly, recovery from illness does not necessarily mean nutritional recovery. Kath described three phases: Acute illness, early recovery and nutritional rebuilding. During recovery, clinicians and families should consider whether appetite and portion sizes have returned to baseline, whether milk or other fluids are displacing food, and whether lost weight has been regained.

With gastroenteritis, the emphasis should move from rehydration to feeding according to tolerance rather than prolonged restriction. Once rehydration is underway and feeding is tolerated, age-appropriate foods can progressively be resumed.

Small appetite, big nutritional needs

Low appetite is an important clinical clue, but it is not a diagnosis. The next question should be why the child is not hungry. Possible contributors include recent illness, constipation, reflux, nausea, medication effects, excessive milk or juice, grazing, fatigue, anxiety and sensory difficulties.

For children who cannot manage larger portions, increasing nutrient density may be more practical than simply asking them to eat more. Foods can be fortified with energy-dense ingredients, while attention should be given to reliable sources of protein, iron, calcium, fibre and essential fatty acids. The principle is simple: A small appetite does not mean small nutritional requirements.

Selective eating is common, but nutritional compromise is not inevitable. The clinical concern increases when restricted variety, low volume and prolonged mealtimes occur together, particularly when entire food groups disappear from the diet, growth begins to decelerate or mealtimes become distressing.

Constipation is another potentially overlooked contributor. Abdominal fullness and discomfort can suppress appetite, creating a cycle in which reduced food and fluid intake worsens constipation. Assessing stool consistency, painful defecation, withholding behaviour, bloating and soiling can therefore be an important part of assessing poor appetite.

Growth, puberty and activity

Childhood and adolescence are periods when nutrition must simultaneously support basic function, growth and physical activity. Increased sporting activity can create a nutritional gap when training increases but food intake does not.

Puberty represents a particularly important nutritional season because energy requirements rise alongside growth and activity. Protein supports new tissue and recovery, while iron becomes particularly important as blood volume and lean tissue expand. Calcium and vitamin D are central to skeletal development.

Fatigue, reduced endurance, poor recovery, recurrent illness, declining training tolerance or changes in growth should therefore prompt consideration of whether nutritional intake is keeping pace with demand.

For young athletes, the priority is to fuel the child first and the athlete second. Training should be supported by appropriate nutrition before and after activity, while growth remains a nutritional priority.

When food first is not enough

Food-first strategies remain an important starting point when a child is clinically stable and can safely meet their requirements orally. Meals and snacks can be fortified, accepted foods optimised, eating opportunities structured and barriers such as constipation or feeding difficulties addressed.

However, food first should not become food only at all costs. Persistent low intake, weight loss, growth faltering, increased requirements, chronic disease, feeding difficulties or poor tolerance of food volume may require escalation to oral nutritional supplementation or, when necessary, enteral support.

Crucially, supplementation should address an identified gap rather than simply add more nutrients. McGaw recommends considering whether a deficiency is documented or clinically likely, defining the purpose of supplementation, selecting an appropriate dose and duration, and establishing a review point. Clinicians should also ask about all other supplements a child is receiving to avoid unnecessary duplication or ‘nutrition stacking’.

Ultimately, nutritional intervention should be a cycle of assessment, intervention and review. Identify what has changed, plot the growth trajectory, identify the nutritional gap, intervene at the appropriate level and review the response. Recognising nutritional vulnerability before the gap becomes too large may provide a valuable opportunity to protect a child’s growth, development and function.

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