6. Conclusions

Low or restricted energy intakes reduce the physical activity of infants and children, even at a very early age. When this is transient, it will be reversed rapidly with nutritional improvement, and it may have no important morphologic, functional, or behavioral consequences. However, a prolonged reduction in physical activity due to sustained low energy intake, may limit or reduce the child's social interactions and exploration of its environment. This is more evident under circumstances where children are encouraged or forced to participate in very energy-demanding activities. These include games, sport competitions and the need to work in rural areas.

Such limitations may contribute to a slower cognitive development, suboptimal social performance, smaller body size and reduced productivity in physical work. All this, in turn, will hinder the child's development to its full biological potential, reduce its quality of life in a broad sense, and limit its contributions to family welfare, either in childhood and adolescence, or in later adult life. Therefore, interventions to improve nutrition and function at an early age, and maintaining them through childhood, will have important biological, social and economic implications.

It is thus inappropriate to refer to the reduction of physical activity as an adaptation to low or restricted energy intake, as this term has the connotation of a desirable, positive adjustment. Under the best circumstances, it should only be considered as an adequate but short-term compensatory response.