Components of Weight at Menarche

Individual girls have menarche at varied weights and heights. To make the notion of a critical weight meaningful for an individual girl, the components of body weight at menarche were analyzed. We investigated body composition at menarche because total body water (TW) and lean body weight (LBW; TW/0.72) are more closely correlated with metabolic rate than is body weight since they represent the metabolic mass as a first approximation. Metabolic rate was considered to be an important clue since Kennedy hypothesized a food intake-lipostat-metabolic signal to explain his elegant findings on weight and puberty in the rat.

The greatest change in estimated body composition of both early and late-maturing girls during the adolescent growth spurt was a large increase in body fat from approximately 5 to 11 kg (a 120% increase) compared to a 44% increase in lean body weight. There was thus a change in the ratio of lean body weight to fat from 5:1 at initiation of the spurt to 3:1 at menarche. The shortest, lightest girls at menarche had a smaller absolute amount of fat (8.9 ± 0.4 kg) compared to the tallest, heaviest girls (12.3 ± 0.6 kg) (the mean of all subjects was 11.5 ± 0.3 kg). However, both extreme groups had approximately 22% of their body weight as fat at menarche, as did all subjects, and the ratio of lean body weight to fat of both groups was in the range of 3:1, as it was for all subjects.

Since adipose tissue can convert androgens to estrogens, the relative degree of fatness can be

18.5

18.5

1800 1820 1840 1860 1880 1900 1920 1940 1960 1980

Calendar year

Figure 2 Mean or median age of menarche as a function of calendar year from 1790 to 1980. The symbols refer to England 0; France •; Germany Holland □; Scandinavia (Denmark, Finland, Norway, and Sweden) X; Belgium, Czechoslovakia, Hungary, Italy, Poland (rural), Romania (urban and rural), Russia (15.2years at an altitude of 2500m and 14.4years at 700m), Spain, and Switzerland, all labeled O; and the United States 0 (data not included in the regression line). Twenty-seven points were identical and do not appear on the graph. The regression line cannot be extended indefinitely. The age of menarche has already leveled off in some European countries, as it has in the United States. (From Wyshak and Frisch (1982) Evidence for a secular trend in age of menarche. New England Journal of Medicine 306: 1033-1035, with permission from the New England Journal of Medicine.)

1800 1820 1840 1860 1880 1900 1920 1940 1960 1980

Calendar year

Figure 2 Mean or median age of menarche as a function of calendar year from 1790 to 1980. The symbols refer to England 0; France •; Germany Holland □; Scandinavia (Denmark, Finland, Norway, and Sweden) X; Belgium, Czechoslovakia, Hungary, Italy, Poland (rural), Romania (urban and rural), Russia (15.2years at an altitude of 2500m and 14.4years at 700m), Spain, and Switzerland, all labeled O; and the United States 0 (data not included in the regression line). Twenty-seven points were identical and do not appear on the graph. The regression line cannot be extended indefinitely. The age of menarche has already leveled off in some European countries, as it has in the United States. (From Wyshak and Frisch (1982) Evidence for a secular trend in age of menarche. New England Journal of Medicine 306: 1033-1035, with permission from the New England Journal of Medicine.)

directly related to the quantity of circulating estrogen. The biological effectiveness of the estrogen is also related to body weight. Rate of fat gain, therefore, is a neat mechanism for relating rate of growth, nutrition, and physical work to the energy requirements for reproduction.

Your Metabolism - What You Need To Know

Your Metabolism - What You Need To Know

If you have heard about metabolism, chances are it is in relation to weight loss. Metabolism is bigger than weight loss, though, as you will learn later on. It is about a healthier, better you. If you want to fire up your metabolism and do not have any idea how to do it, you have come to the right place. If you have tried to speed up your metabolism before but do not see visible results, you have also come to the right place.

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