Body fat, puberty and fertility

An epidemiological study of anorectic and bulimic symptoms in adolescent girls: implications for pediatricians

Our findings suggest that most cases of anorexia nervosa among high school girls are eventually recognized and treated. However, it is worrisome that a large number of girls suffering from early anorexia nervosa and an even greater number suffering from bulimia do not seek treatment for their disorder. In addition, it is clear that girls who do not meet criteria for the full syndromes may nonetheless be engaging in the cardinal behaviors associated with these disorders. Therefore, the pediatrician must actively inquire about weight control practices and binge-purge behavior during the course of routine examinations. These behaviors are sufficiently common that such inquiry should be incorporated into the routine evaluation of every girl, even when there is no obvious reason to be concerned. The vast majority of girls will express dissatisfaction with their weight and report that they have attempted to control their weight in some manner, most often with dieting, in the past year. Normative data from a cross-sectional study such as the one described provide some guidelines as to when such behavior is likely to be associated with other types of problems, such as depressive symptoms or amenorrhea. For example, our data suggest that weight loss of 10 lbs or more in the past year and fasting are more likely to be associated with depressive symptoms and menstrual irregularity than less severe forms of caloric restriction. Our findings also suggest that purging behavior (self-induced vomiting and laxative use), particularly in combination with binge eating, is associated with very high rates of both depressive symptoms and menstrual irregularity.(ABSTRACT TRUNCATED AT 250 WORDS)

Managing the lactating sow for optimal weaning and rebreeding performance

Management of the lactating sow influences milk production and subsequent reproduction through changes in nutrient intake. The management goal during lactation is to maximize feed intake. Decreasing the effective environmental temperature, increasing the nutrient density of the lactation diet, maintaining fresh adequate supplies of feed and water, and preventing excess weight gain during the prior gestation period will increase nutrient intake during lactation. Effective environmental temperature of the lactating sow can be maintained in the thermoneutral zone by using drip cooling, increased ventilation rates and flooring materials with superior conductive properties. Sow parity, genetics, litter size, and disease level will also influence feed intake. Management practices must account for these factors and, thus, should be tailored to individual farm situations to ensure adequate nutrient intake and prevent aberrations in subsequent reproductive performance.

Metabolic fuels and reproduction in female mammals

A complete reproductive cycle of ovulation, conception, pregnancy, and lactation is one of the most energetically expensive activities that a female mammal can undertake. A reproductive attempt at a time when calories are not sufficiently available can result in a reduced return on the maternal energetic investment or even in the death of the mother and her offspring. Numerous physiological and behavioral mechanisms link reproduction and energy metabolism. Reproductive attempts may be interrupted or deferred when food is scarce or when other physiological processes, such as thermoregulation or fattening, make extraordinary energetic demands. Food deprivation suppresses both ovulation and estrous behavior. The neural mechanisms controlling pulsatile release of gonadotropin-releasing hormone (GnRH) and, consequently, luteinizing hormone secretion and ovarian function appear to respond to minute-to-minute changes in the availability of metabolic fuels. It is not clear whether GnRH-secreting neurons are able to detect the availability of metabolic fuels directly or whether this information is relayed from detectors elsewhere in the brain. Although pregnancy is less affected by fuel availability, both lactational performance and maternal behaviors are highly responsive to the energy supply. When a reproductive attempt is made, changes in hormone secretion have dramatic effects on the partitioning and utilization of metabolic fuels. During ovulatory cycles and pregnancy, the ovarian steroids, estradiol and progesterone, induce coordinated changes in the procurement, ingestion, metabolism, storage, and expenditure of metabolic fuels. Estradiol can act in the brain to alter regulatory behaviors, such as food intake and voluntary exercise, as well as adenohypophyseal and autonomic outputs. At the same time, ovarian hormones act on peripheral tissues such as adipose tissue, muscle, and liver to influence the metabolism, partitioning and storage of metabolic fuels. During lactation, the peptide hormones, prolactin and growth hormone, rather than estradiol and progesterone, are the principal hormones controlling partitioning and utilization of metabolic fuels. The interactions between metabolic fuels and reproduction are reciprocal, redundant, and ubiquitous; both behaviors and physiological processes play vital roles. Although there are species differences in the particular physiological and behavioral mechanisms mediating nutrition-reproduction interactions, two findings are consistent across species: 1) Reproductive physiology and behaviors are sensitive to the availability of oxidizable metabolic fuels. 2) When reproductive attempts are made, ovarian hormones play a major role in the changes in ingestion, partitioning, and utilization of metabolic fuels.

Adolescent smoking, weight changes, and binge-purge behavior: associations with secondary amenorrhea

BACKGROUND

The association of secondary amenorrhea with extreme forms of substance use, weight control, and exercise in nonrepresentative samples raises questions as to whether adolescents in the general population who engage in these behaviors are at increased risk for secondary amenorrhea. We examined the prevalence and behavioral correlates of secondary amenorrhea in a county-wide high school population of 2544 girls aged 13 to 18.

METHODS

A survey questionnaire, which elicited menstrual history as well as weight history, weight control practices, level of exercise, and use of cigarettes, wine, and beer, was administered during school hours; absentees were also surveyed. The completion rate was 91%.

RESULTS

The 1-year prevalence of secondary amenorrhea was 8.5%. Secondary amenorrhea was associated with smoking one or more packs of cigarettes per day (adjusted relative risk [RRa] = 1.96, 1.21-3.10), with multiple binge-eating behaviors in combination with laxative use or self-induced vomiting (RRa = 4.17, 2.54-6.32), and with weight fluctuation due to weight control (RRa = 2.59, 1.33-4.79). There was no association between amenorrhea and alcohol consumption or exercise level.

CONCLUSIONS

Estimates of attributable risk are provided and indicate that bulimic behaviors and cigarette smoking may result in a considerable excess of cases of secondary amenorrhea in an adolescent population.

Body-fat measurements and athletic menstrual irregularity

The purpose of this study was to compare four measurements used as estimates of body fat that have been used in previous studies to determine whether the association between body fat and athletic menstrual irregularity (AMI) is measurement dependent. In a sample of 112 marathon runners, 94 responded to questions regarding their menstrual cycle. Of these, 30 (32%) reported irregular or absent menses, and 64 (68%) reported regular menses. Of the 30 subjects reporting menstrual irregularities or amenorrhea, 13 (43%) reported having had menstrual irregularity or amenorrhea prior to taking up running. Estimates of body fat were based on Mellits and Cheek's (1970) equation for estimating percentage of body water, Lutter and Cushman's (1982) height and weight categories, actual gross body weight, and weight loss of 10 lb (4.5 kg) or more since taking up the sport. In this sample of marathon runners, none of the four methods used to estimate body fat supported a relationship between menstrual irregularity and low body fat. A significant (p less than .001) relationship was found between prior menstrual irregularity and the development of AMI after starting to run.

Lability of fat stores in peripubertal wild house mice

Traditionally, the adaptive value of mammalian white fat stores is considered in relation to long-term needs such as providing protection against the vagaries of winter or signalling the reproductive system when energy reserves are sufficient to risk pregnancy. As shown here, the fat stores of young house mice could not serve such needs. Despite prolonged acclimation and excess nesting material, food deprivation at 10 degrees C significantly lowered the fat stores of peripubertal female house mice in only 12 h, and would exhaust them in 30 h. Even close to thermoneutrality (24 degrees C) the calculated time to exhaustion was only 70 h. The fat stores of a young house mouse are obviously too meager to offer any meaningful protection over a winter of several months duration, or even over a 5-6-week cycle of pregnancy and lactation. Furthermore, in a wild habitat where food availability and ambient temperature can vary rapidly and greatly, such fat stores would be too labile to effectively coordinate puberty with somatic development.

Menstrual patterns in Danish elite swimmers

Questionnaires were given to 140 female elite swimmers from the highest ranking division in the Danish Swimming Association inquiring about their menstrual history. Eighty-nine percent completed the questionnaires. We found a very low incidence of menstrual dysfunction (16%) compared to other groups of endurance trained females. Hard physical endurance training did not seem to delay the onset of menarche among swimmers. Furthermore, no difference in adjusted body mass between a group with oligomenorrhoea and a normal menstruating group could be demonstrated. The study indicated that the influence of body mass or body fat content was a more important factor in menstrual function than the amount of training or psychological stress.

The right weight: body fat, menarche and ovulation

Women with moderate weight loss (10-15% of ideal weight), as well as women with the severe weight loss of anorexia nervosa (30% of ideal weight), have secondary or primary amenorrhoea. A high proportion of well-trained dancers and athletes also have amenorrhoea, though weight may be in the normal range, since muscles are heavy (80% water, compared to 5-10% water in adipose tissue). The amenorrhoea is usually reversible with weight gain, decreased exercise or both. The amenorrhoea is due to hypothalamic dysfunction; the pituitary-ovary axis is intact, suggesting that this type of amenorrhoea is adaptive, preventing an unsuccessful pregnancy outcome. Evidence is presented that the high percentage of body fat (26-28%) in mature women is necessary for regular ovulatory cycles. Target weights for height are given for the evaluation and treatment of primary and secondary amenorrhoea due to weight loss. The high percentage of body fat in women may influence reproductive ability directly: (1) as an extragonadal source of oestrogen by aromatization of androgen to oestrogen; (2) by influencing the direction of oestrogen metabolism to more potent or less potent forms; or (3) by changes in the binding properties of sex-hormone-binding globulin. Indirect signals may be of abnormal control of temperature and changes in energy metabolism, which accompany excessive leanness.

Effects of interactions between photostimulation, dietary restriction and dietary maize oil dilution on plasma LH and ovarian and oviduct weights in broiler breeder females during rearing

1. The response of the reproductive system to photostimulation was investigated during the rearing period in dwarf broiler breeder females maintained from hatch on 8 h light/d. The effect of increased body fat on this response was investigated. Body fat was increased by diluting the diet with maize oil. 2. A significant increase in plasma luteinising hormone (LH) was observed 4 d after photostimulation with 20 h light/d at 3 and 15 weeks of age in birds fed the restricted diet alone and at 3, 7, 11, 15 and 19 weeks of age in birds fed the restricted diet diluted with maize oil. 3. Increases in ovarian weight were observed two weeks after photostimulation at 15 weeks of age in birds fed the restricted diet alone and at 7, 11 and 15 weeks of age in birds fed the restricted diet diluted with maize oil. Increases in oviduct weight were seen after photostimulation at 11, 15 and 19 weeks of age in both dietary treatment groups; however, a larger increase in oviduct weight was seen at 15 and 19 weeks of age in birds fed the restricted diet diluted with maize oil. 4. In a second experiment, the dilution of a diet fed ad libitum with maize oil significantly increased body fat content and the baseline concentration of LH but did not enhance the response of the reproductive system to photostimulation. 5. Baseline plasma LH concentrations were lower in birds fed ad libitum than in those fed a restricted diet. 6. It is concluded that the neuroendocrine pathways involved in the transmission of photoperiodic information are functional at 3 weeks of age. The function of the components of the hypothalamo-pituitary complex which control reproductive activity is enhanced when a restricted diet diluted with maize oil is fed.

Anorexia nervosa, athletics, and amenorrhea

Menstrual dysfunction is common in adolescents who are involved in intensive athletic activity or who are limiting their nutritional intake excessively. The mechanism for hypothalamic amenorrhea in athletes and dieters is not yet fully understood. Other causes of menstrual dysfunction due to pregnancy, central lesions, hormone imbalance, or ovarian failure should be excluded in the athlete with amenorrhea. Amenorrheic patients who have sufficient estrogen effect on their endometrium to have withdrawal bleeding following exposure to progestins should be cycled with progestins on a regular basis to prevent endometrial hyperplasia. Estrogen replacement with cyclic progestin should be considered in the hypoestrogenic adolescent with prolonged amenorrhea. The long-term consequences of hypothalamic amenorrhea in adolescents remain to be determined.

Effects of dietary trans-fatty acids on reproductive performance of Wistar rats

1. Wistar rats were fed for three successive generations on a semi-purified diet, in which the fat was provided by butter, sunflower oil, rapeseed oil or hydrogenated vegetable fat, differing in the content of cis,cis-18:2 and trans-18:1 fatty acids. Effects of these fats on the composition of adipose tissue and reproductive performance were studied. Fatty acids were analysed using high-performance liquid chromatography. 2. The fatty acid pattern of adipose tissue was closely related to dietary fat composition and, established in the first generation, did not change significantly in successive generations of rats. 3. Hydrogenated fat adversely affected litter size, sperm morphology and regularity of oestrous cycle, and prolonged the period of gestation in experimental animals. Differences observed between the generations were not significant. 4. Hydrogenated fat decreased the level of serum testosterone in males, but the differences observed in levels of serum progesterone in females were not apparently related to the dietary trans-fatty acids.

Body composition and other physical parameters as determinants of age at sexual maturity and performance efficiency in dwarf hens divergently selected for body weight

Hens in this study were produced from random breeding within lines (high, low, and control) of dwarf White Leghorns that had been divergently selected for four generations for 20-week body weight. Birds were weighed at 10 weeks of age and placed in individual cages at 18 weeks of age. Body weights, shank lengths, and egg weights were obtained at sexual maturity (day of first egg) and at 4, 8, 12, and 16 weeks after sexual maturity. Egg production was recorded during 28-day periods. Thirty hens/line were sampled at sexual maturity and at the above times after sexual maturity for body composition (percent fat, protein, moisture, and ash). High line hens showed increased percent body fat and reduced percent protein and moisture compared to low and control hens. Coefficients of determination (R2) for age at sexual maturity and body weight were small (R2 less than or equal to .20) for high and control hens. There were no meaningful relationships between body weight or other physical measurements and sexual maturity in low hens. There were no significant relationships between body composition and age at sexual maturity in high and control hens. There was a strong cubic association (R2 = .73; P less than .001) between percent ash and age at sexual maturity in low hens, although the biological importance of this relationship was uncertain. Coefficients of determination between body weight and performance efficiency (egg mass per body weight) were small to moderate (R2 = .04 to .46) for high and control hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Recalled age of menarche in Britain

The purpose of this study was to determine recalled age at menarche from the National Child Development Survey of all children born in Britain in one week of 1958. All subjects were questioned at the same age (16 years); mean age at menarche was estimated as 13.3 +/- 0.02 years. The data deviate significantly from normality. Marked regional variation occurred but very little social class differentiation was apparent.

Metabolic changes during maturation of male monkeys: possible signals for onset of puberty

There is a close relationship between the metabolic status of a maturing animal and the timing of puberty onset. However, the signals linking metabolic status to the maturation of the reproductive axis remain unknown. We looked for metabolic differences before and after puberty by comparing plasma profiles of insulin, glucose, amino acids, beta-hydroxybutyrate, and glycerol between juvenile and adult monkeys in fed and fasted states. Thirteen juvenile and 13 adult male crab-eating macaques (Macaca fascicularis) were fed a mixed meal, and blood samples were collected at intervals between 1.5 and 52 h after the meal. Plasma insulin concentrations decreased in a similar manner in both groups during the first 16 h of fasting. By 20 h after a meal, basal insulin levels were significantly lower (P less than 0.025) in juveniles compared with adults and remained so until the end of the fast. Circulating levels of glucose were similar in juveniles and adults immediately after a meal and then decreased significantly (P less than 0.025) in juveniles by 28 h of fasting and in adults by 52 h of fasting. Plasma concentrations of all large neutral amino acids (i.e., tyrosine, tryptophan, phenylalanine, valine, leucine, and isoleucine, LNAA) except tryptophan decreased more precipitously in juveniles than in adults during the first 20 h of fasting. However, the ratios of tyrosine to other LNAA and tryptophan to other LNAA were similar in juveniles and adults at all times. beta-Hydroxybutyrate concentrations were low in both groups until 24 h after a meal, at which time plasma levels increased more rapidly and attained higher values in juveniles compared with adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Patterns of mortality and age at first reproduction in natural populations of mammals

There is great variation in the age at which females of different mammalian species first breed. Recent comparative analyses have focused on the relationship between age at first reproduction and body size, but differences in patterns of mortality experienced by natural populations are expected to have major effects on selection for age at first reproduction. Here we show that the age at which females first reproduce is strongly correlated with expectation of life at birth, after the effects of body size have been removed, within and among species of mammals living in natural populations.

The investigation of female gonadal dysfunction

An approach to the investigation of ovarian dysfunction has been presented here with a particular emphasis on the importance of effective imaging of the ovary and uterus by ultrasonography. Essential endocrine investigations in the various clinical manifestations of altered ovarian function have been placed in the context of recent research on the control of female reproduction.