The fastest growing age period is infancy; in addition, a second growth spurt occurs during puberty, which can often be reflected in the level of growth and development by increases in height and weight.
Infancy is the period from birth to 1 year of age, and puberty is the period from about 10 to 18 years of age.
In the first year of life, weight gain is 6 kg; in the second year of life, weight gain is 3 kg; thereafter, weight gain is about 2 kg per year until puberty; weight can increase rapidly again during puberty, and the degree of increase varies from person to person.
In the first year of life, the height increases by 25cm; in the second year of life, the height increases by 12cm; thereafter, the height increases by about 6-7cm per year until puberty; the height can increase rapidly during puberty.
Therefore, the fastest growth is before the age of 1 year, i.e. infancy; the second fastest growth is during puberty.