Complex sentence: In a newborn infant, this may be as high as 79 percent of the body weight, but it progressively decreases from birth to old age, most of the decrease occurring during the first 10 years of life.
Split into simpler sentences: In a newborn infant, this may be as high as 79 percent of the body weight, but it progressively decreases from birth to old age. Most of the decrease occurring during the first 10 years of life.