Babyhood is the period which baby grows and develops very quickly, baby needs to absorb the sufficient energy to ensure the normal growing development. If total calories cannot be supplied adequately for a long-term that will lead to stunt, reduce resistivity and suffer from diseases easily; however, excessive absorption may lead to obesity. Therefore, appropriate energy intake of every day will benefit baby's growing development.
The energy needs of baby include the following five aspects:
（1）Basal metabolism: higher than adult, calculate according to per kilogram of avoirdupois per day, baby within one-year-old needs about 230.2KJ (55KCal), twelve-year-old baby needs 184.2KJ (44KCal), and baby after 7-year-old needs 104.6~125.6KJ (25~30KCal) which is similar to adult's.
（2）The activity needs: the newborn baby can only cry and suckle, this requires less energy, baby needs about 62.8~83.7KJ(15～20KCal/kg•d), the requisite amount will be increased by the growing of the ages, 12-year-old baby needs about 125.6KJ/kg•d（30KCal/kg•d）.
（3）The growth needs: this part of thermal energy consumption is especially for baby. The quantity of heat which required by baby and the growth speed are proportional, if the quantity of heat provided by diet is insufficient, the growing development will be halted or delayed. This quantity of heat approximately composes 25～30%. Newborn baby needs 167.4～209.3KJ（40～50KCal/kg•d), 1-year-old baby needs 62.8KJ（15KCal). Every 1kg of weight increasing needs to intake 18410～23849KJ of energy.
（4）Food specific dynamic action: although the proportion of protein in baby's diet is higher than adults, the food specific dynamic action in baby's diet is low, with an average of 6% of total calories, which is similar to adults.
（5）Excretion consumption: the food which everyday takes cannot be absorbed completely. Part of food is excreted without digestion and absorption, the loss of this quantity of heat does not exceed 10%, but when baby has diarrhea, the loss of heat will increase.
In summary, the heat which baby needs to maintain the resting state (including basal metabolism and food specific dynamic action), is accounting for about 50%, calories needed for growing development accounts for 25%, as well as the calories needed for activity. Calculate according to unit surface area, the energy needed of baby is the highest one. If the supplement of total heat is insufficient, which will lead to emaciation, stunt, no increase of weight, the resistance lowered and will suffer from diseases easily. But the long-term excessive supplements of total heat will cause obesity.
In practical application, we estimate the needs of total calorie mainly according to baby's age and weight. The calorie everyday needed for each kilogram of weight: newborn baby needs 60KCal on the first week, 100KCal is needed on the second to the third week, when baby in the second to sixth month, he needs approximately 110～120KCal. The simple calculation method is: 110KCal/kg•d in 1-year-old, and after that every 3 year deduct 10KCal, about 60KCal in 15-year-old and 30KCal for adults.