Experimental: Standardized nutrition management（+ short peptide ONS) Group

The children in this group will be given standardized nutrition management after admission. They will follow the five-step treatment principle of malnutrition. Diet + nutrition education is the basic way, which is successively promoted to diet + oral nutrition supplement, enteral nutrition, partial enteral nutrition + supplementary parenteral nutrition, and total parenteral nutrition. When a nutritional treatment does not meet 60% of the target energy requirements for 3 to 5 days, the upper step of the treatment can be selected. For infants or newborns, when 75-80% of the target amount cannot be reached for 3-5 days, the upper step of the treatment can be selected.~During the study period, an additional 3 months of short peptide oral nutritional supplements (ONS) is expected to be performed in children enrolled from December 1, 2024 to February 28, 2025 to explore the improvement of the nutritional status of the children.

No_intervention: Control group

Clinical variables, biochemical markers, dietary data, and physical activity data will be collected at baseline and at each visit (admission to hospital, 1, 2, 3, 6, 12, 18, and 24 months after diagnosis).