programming,social patterning effects have to be considered.Adolescence may be a particularly relevant time for social patterning influences At least in certain population groups,another long-term benefit of improved nutrition in adolescence, particularly in girls,is the reduced risk of osteoporosis in older age.Calcium intake and bone deposition in adolescence are key factors of bone mineral mass later on in life,along with other determinants(see Chapter 3). Influencing nutrition-related behaviours of adolescents implies that they have some choice and,therefore, that they have access to the required food resources.This may not be so as adolescents generally have less resources than adults,while being more on their own than younger children.This is why interventions to enhance economic and food security of adolescents and more generally of households may be required in order for nutrition intervention to have sustainable impact.Conversely,improved health and nutrition may positively affect productivity and,therefore,long-term economic and food security(Delisle 1998a). 2.3 There is potential for correcting nutritional inadequacies and perhaps even for catch-up growth Adolescence is commonly regarded as a relatively healthy period of the life cycle.Indeed,adolescents are possibly less vulnerable to infection than they were at a younger age.This may contribute to their being somewhat neglected,but also it may mean that there is at adolescence less interference with adequate physiological utilization of food nutrients. Once final height is attained,stunting becomes a permanent consequence of past malnutrition rather than being a sign of present malnutrition.Growth retardation is common in poorer countries,and it occurs primarily during the first three years of life.The growth spurt of adolescence has been seen as a period of potential interest for catching up growth deficit of childhood.If there is indeed catch-up growth in height,adolescence can provide a final chance for intervention to promote additional growth, with potential benefit in terms of physical work capacity and for girls,of diminished obstetric risk(see also Chapter 3).However,evidence confirming catch-up growth during adolescence is still limited,and mostly indirect.Prolongation of the growth period due to delayed maturation associated with malnutrition can make up for some of the earlier growth retardation,in other words,there is some degree of spontaneous catch-up(Golden 1994).It is suggested,however,that total reversal to affluent societies'levels of final height would probably require cross-generational catch-up.A review of adopted children's studies suggests that catch-up growth through accelerated growth rates can be quite pronounced,but that it is not complete,and that it would be minimal in populations which continue to reside in the same place (Martorell,Kettel Khan and Schroeder,1994).It is possible that nutritional interventions induce an earlier and accelerated growth spurt,but it is not sure,based on available evidence, that it will affect final attained adult height,since it may then accelerate maturation,with a shortened growth period as a result.Remedial action in adolescence would be considered as coming late compared to that undertaken in infancy,but it may still be relevant,if shown to be effective in increasing lean body mass.However,catch-up growth intervention in adolescence will likely not improve other consequences of early growth retardation,in particular learning impairment(Martorell,Kettel Khan and Schroeder, ibid.).Furthermore,in adolescents who were born small because of intrauterine growth retardation, nutritional intervention for catch-up growth may result in gain in fat rather than in height(Leger and Czernichow,1999),as such individuals appear more prone to becoming obese. Studies undertaken as part of the adolescent research programme of the International Center for Research in Women(ICRW)contributed to knowledge about the extent of catch-up growth in height during adolescence,in the absence of or with food supplementation(Kurz and Johnson-Welch,1994).In the Philippines,it was found that over an eight-year period,adolescents aged 11-20 years from lower income households had completely caught up with those in the higher group,without supplementation.Findings from the Mexico study suggest partial spontaneous catch-up growth during adolescence.Children who were supplemented from the age of three months up to 10 years were still taller at age 18 than the non-8/ programming, social patterning effects have to be considered. Adolescence may be a particularly relevant time for social patterning influences. At least in certain population groups, another long-term benefit of improved nutrition in adolescence, particularly in girls, is the reduced risk of osteoporosis in older age. Calcium intake and bone deposition in adolescence are key factors of bone mineral mass later on in life, along with other determinants (see Chapter 3). Influencing nutrition-related behaviours of adolescents implies that they have some choice and, therefore, that they have access to the required food resources. This may not be so as adolescents generally have less resources than adults, while being more on their own than younger children. This is why interventions to enhance economic and food security of adolescents and more generally of households may be required in order for nutrition intervention to have sustainable impact. Conversely, improved health and nutrition may positively affect productivity and, therefore, long-term economic and food security (Delisle 1998a). 2.3 There is potential for correcting nutritional inadequacies and perhaps even for catch-up growth Adolescence is commonly regarded as a relatively healthy period of the life cycle. Indeed, adolescents are possibly less vulnerable to infection than they were at a younger age. This may contribute to their being somewhat neglected, but also it may mean that there is at adolescence less interference with adequate physiological utilization of food nutrients. Once final height is attained, stunting becomes a permanent consequence of past malnutrition rather than being a sign of present malnutrition. Growth retardation is common in poorer countries, and it occurs primarily during the first three years of life. The growth spurt of adolescence has been seen as a period of potential interest for catching up growth deficit of childhood. If there is indeed catch-up growth in height, adolescence can provide a final chance for intervention to promote additional growth, with potential benefit in terms of physical work capacity and for girls, of diminished obstetric risk (see also Chapter 3). However, evidence confirming catch-up growth during adolescence is still limited, and mostly indirect. Prolongation of the growth period due to delayed maturation associated with malnutrition can make up for some of the earlier growth retardation, in other words, there is some degree of spontaneous catch-up (Golden 1994). It is suggested, however, that total reversal to affluent societies’ levels of final height would probably require cross-generational catch-up. A review of adopted children’s studies suggests that catch-up growth through accelerated growth rates can be quite pronounced, but that it is not complete, and that it would be minimal in populations which continue to reside in the same place (Martorell, Kettel Khan and Schroeder, 1994). It is possible that nutritional interventions induce an earlier and accelerated growth spurt, but it is not sure, based on available evidence, that it will affect final attained adult height, since it may then accelerate maturation, with a shortened growth period as a result. Remedial action in adolescence would be considered as coming late compared to that undertaken in infancy, but it may still be relevant, if shown to be effective in increasing lean body mass. However, catch-up growth intervention in adolescence will likely not improve other consequences of early growth retardation, in particular learning impairment (Martorell, Kettel Khan and Schroeder, ibid.). Furthermore, in adolescents who were born small because of intrauterine growth retardation, nutritional intervention for catch-up growth may result in gain in fat rather than in height (Léger and Czernichow, 1999), as such individuals appear more prone to becoming obese. Studies undertaken as part of the adolescent research programme of the International Center for Research in Women (ICRW) contributed to knowledge about the extent of catch-up growth in height during adolescence, in the absence of or with food supplementation (Kurz and Johnson-Welch, 1994). In the Philippines, it was found that over an eight-year period, adolescents aged 11-20 years from lower income households had completely caught up with those in the higher group, without supplementation. Findings from the Mexico study suggest partial spontaneous catch-up growth during adolescence. Children who were supplemented from the age of three months up to 10 years were still taller at age 18 than the non-