Adequate nutrition is essential for normal growth at all ages. Malnutrition delays growth. The period when the child is most at risk from the combination of malnutrition and infection is from birth to 5 years. Many populations in developing countries have mean birth weights at the same level as those in developed countries but it is only after 6 months that the weight gains diminish as a result of the interaction of undernutrition and infection. The slowing down in weight growth in some areas coincides with age of weaning and the substitution of high starch, low protein foods. It is also the age at which the mother’s lactating ability declines so that satisfactory growth cannot be achieved by breast milk alone.
Researchers have discussed the question of whether under nutrition in the first or second year of life necessarily leads to an adult deficit on body size. It has been seen that children with severe protein-calorie malnutrition in early infancy due to malformations or malfunction of the gut make a complete recovery in height after surgical correction when brought in well off homes in a developed country.
Evidently much depends on the circumstances when the severe episode of malnutrition is over. Children less than five years admitted to hospital in tropical countries with severe protein-calorie malnutrition (Kwashiorkor or Marasmus) were followed after discharge. In most of such children complete equality of height and weight with sibling controls was attained before puberty. In other long term deficits were reported and their growth was not equal to their siblings but was more close to the general population, a less appropriate control. Long periods of under nutrition, often combined with chronic infections; certainly have lasting effects on body size.
Body shape is made more resistant to nutritional stress or even disease than is body size. Malnutrition in man does not alter significantly the shape of the body; a malnourished European child by no means acquires the short legs of the Asiatic. These days along with malnutrition, overweight is also causing an increasing problem of obesity not only in developed countries but also in developing countries. Recent evidence suggests that overfeeding in first year or 18 months after birth may have much to do with the tendency to become obese later.
During the period of 5 years to adolescence the child is growing less rapidly and presumably because of this few populations show height and weight means decreasing further. A second period when the child may be especially sensitiveto influence of under nutrition is at adolescence. The calorie requirement increases at this time in level with the increased growth of the adolescent spurt. Lack of sufficient calories may result either in a smaller spurt or a delay in the age of the spurt. The latter reflects chiefly on accumulating deficit in the years preceding adolescence. Tempo seems usually to be first thing affected. In data from well off families in all populations, age at menarche is earlier than children from underprivileged section. Girls from larger families also had consistently late maturation than those from smaller ones. Poor nutrition during childhood slows up skeletal maturation and also affects width of cortical bone. Thus, level of nutrition of children in a population has to be studied in relation to their ecological aspects and most importantly its implications on human growth and maturation.