REVIEW Impact of the Menstrual Cycle on Determinants of Energy Balance: a Putative Role in Weight Loss Attempts

Home , Follicular phase, Luteal phase

International Journal of Obesity (2007) 31, 1777–1785 & 2007 Nature Publishing Group All rights reserved 0307-0565/07 $30.00 www.nature.com/ijo REVIEW Impact of the menstrual cycle on determinants of energy balance: a putative role in weight loss attempts

L Davidsen, B Vistisen and A Astrup

Department of Human Nutrition, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark

Women’s weight and body composition is significantly influenced by the female sex-steroid hormones. Levels of these hormones fluctuate in a defined manner throughout the menstrual cycle and interact to modulate energy homeostasis. This paper reviews the scientific literature on the relationship between hormonal changes across the menstrual cycle and components of energy balance, with the aim of clarifying whether this influences weight loss in women. In the luteal phase of the menstrual cycle it appears that women’s energy intake and energy expenditure are increased and they experience more frequent cravings for foods, particularly those high in carbohydrate and fat, than during the follicular phase. This suggests that the potential of the underlying physiology related to each phase of the menstrual cycle may be worth considering as an element in strategies to optimize weight loss. Studies are needed to assess the weight loss outcome of tailoring dietary recommendations and the degree of energy restriction to each menstrual phase throughout a weight management program, taking these preliminary findings into account. International Journal of Obesity (2007) 31, 1777–1785; doi:10.1038/sj.ijo.0803699; published online 7 August 2007

Keywords: menstrual cycle; weight loss attempts; energy intake; energy expenditure; food cravings; mood

Introduction Weight loss strategies include eating fewer calories, eating less fat or carbohydrate, exercising more, skipping meals, Around the world obesity is becoming an increasing problem attending weight loss programs, taking diet pills or diuretics and it is accompanied by major health consequences for the and even fasting for more than 24 h.1 Americans spend more individual and society. This has prompted more people to than $33 billion on weight loss products and services every attempt to prevent weight gain, or to lose weight, by altering year.1 However, despite the numerous strategies used, the dietary habits, eating behavior and physical activity. The prevalence of obesity is still increasing. More than 30% of National Health Interview Survey conducted in 1998, which Americans are now obese,3 and increasing prevalences are included 32 440 Americans, showed that 24% of the male reported from most other parts of the world.4–7 For those and 38% of the female population were trying to lose who achieve weight loss, scientific evidence indicates that weight.1 The percentage of the population attempting to lose only 23% of the initial weight loss is sustained 5 years after weight rose as body mass index (BMI) increased. In men the completing a structured weight loss program.8 number trying to lose weight climbed from 6% in the normal When commencing with a diet, cosmetic factors are weight population (BMIo25) to 50% in the obese popula- clearly important motivational factors especially for women, tion (BMIX30). For women the comparable estimates were who appear more motivated to diet because of dissatisfaction 24 and 58%, respectively. In a Danish study interviews with with their body appearance than men.1 Nevertheless, 1200 men and women revealed that approximately half of women may have more difficulty in losing weight, and this population had attempted to lose weight.2 Also here the generally lose less weight than men during weight manage- prevalence of trying to lose weight increased with BMI. ment programs.9,10 This may partly be due to gender differences in energy metabolism and in appetite control brought about by secretion of reproductive hormones. In Correspondence: L Davidsen, Department of Human Nutrition, Faculty of Life women these hormones control the menstrual cycle and Sciences, University of Copenhagen, Rolighedsvej 30, DK-1958, Frederiks- coordinate changes in energy intake (EI), expenditure and berg, Denmark. storage, while preparing the body for pregnancy every E-mail: [email protected] 11 Received 26 September 2006; revised 29 May 2007; accepted 4 June 2007; month. As reproduction is a primary biological function, published online 7 August 2007 these hormones may be such strong mediators of eating Menstrual cycle and energy balance L Davidsen et al 1778 behavior that they influence the outcome of a weight loss the release of LH and FSH from the anterior pituitary, which attempt. The menstrual cycle should therefore be taken into in turn stimulate release of estrogens and progesterone from consideration as a factor in the physiology of energy balance the ovaries.22 in premenopausal women. This paper reviews the literature In the early follicular phase follicular enlargement begins on appetite, cravings, pattern of food intake, energy and is characterized by high circulating levels of FSH, which metabolism and mood across the menstrual cycle. An in- stimulate follicular growth. Levels of plasma LH, estradiol depth understanding of any mechanisms that change and progesterone are low in this phase. Plasma FSH induces a determinants of energy balance during the course of the rise in the concentration of estradiol, which starts in the mid menstrual cycle could provide helpful tools for the preven- follicular phase and continues until the late follicular phase, tion and treatment of obesity. The potential of the when it finally peaks. This event triggers the mid cycle LH physiology related to each phase of the menstrual cycle to surge, which lasts for 40–48 h and induces ovulation. optimize weight loss outcome is discussed. Consequently, the level of plasma estradiol decreases, though it remains slightly elevated throughout the luteal phase.20 When ovulation has occurred progesterone is secreted and Hormonal changes during the menstrual cycle its concentration increases until it reaches its peak in the mid luteal phase, and LH and FSH return to their previous levels. The menstrual cycle is coordinated by the hypothalamic – If the ovum is not fertilized the plasma concentrations of pituitary – gonadal (HPG) axis and is influenced by estradiol and progesterone drop at the end of the luteal physiological and pathological changes that occur through- phase, which initiates menstruation and thereby a new out life.12 The menarche (the first menstruation) is often menstrual cycle.23 The cyclic changes in hormones and body considered the central event of female puberty, as it signals temperature are illustrated in Figure 1. the commencement of fertility. The average age for menarche is between 12 and 13.5 years.13 It seems to occur most frequently when a young woman reaches around 17% Energy intake body fat.14 However, it may not be the amount of body fat per se that affects the timing of menarche. Height, weight It has been observed in animal studies that EI is reduced at 15 and skinfold thickness all appear to play a role. Race and the time of ovulation, when plasma estrogen levels peak, and socioeconomic status have also been suggested to influence that EI is increased after ovulation, when plasma progester- menarcheal age.15,16 The menstrual cycle continues until the onset of menopause around the age of 5017 when the ovaries stop producing estrogens. The reproductive system then Luteinizing hormone 18 gradually shuts down. Follicle stimulating hormone In the majority of women the menstrual cycle averages 28 days, where the day of onset of menstruation is generally referred to as day 1.19 The cycle can be divided into four phases: menstruation or early follicular phase (days 1–4), late follicular phase (days 5–11), periovulation (days 12–15) and the luteal Oestrogen phase (days 16–28).19 The culmination of the follicular phase occurs when ovulation takes place around day 14 or 15. After ovulation the luteal phase begins and lasts about 14 days until the onset of the next menstruation.20 However, when studying Progesterone energy balance across the menstrual cycle it is often divided into two phases separated by menstruation, with a pre- and 19 37°C postmenstrual phase, which is also the case for several of the Temperature studies included in this review. 36°C

The predominant hormones that regulate the menstrual Ovulation cycle are gonadotropin-releasing hormone (GnRH), follicle- Follicular phase Luteal phase stimulating hormone (FSH), luteinizing hormone (LH), Menses progesterone and estrogen.20 There are three major forms of estrogen: estradiol, estrone and estriol. Estradiol is the day 1 day 14 day 28 most potent of these.21 Hormones are secreted at various sites. GnRH is secreted by Figure 1 The menstrual cycle: changes in hormones and in body temperature. Modified from Wikipedia.org. This Wikipedia and Wikimedia the hypothalamus, the gonadotropins FSH and LH are Commons image is from the user Chris 73 and is freely available at http:// secreted by the anterior pituitary gland and estrogens and commons.wikimedia.org/wiki/Image:MenstrualCycle.png under the creative progesterone are secreted from the ovaries. GnRH stimulates commons cc-by-sa 2.5 license.

International Journal of Obesity Menstrual cycle and energy balance L Davidsen et al 1779 one is elevated.24–30 Consequently, it has been hypothesized luteal phase, where women’s EI is increased, are somewhat that estrogens reduce appetite and EI and are thus reciprocal higher compared to levels in the early follicular phase, in to a possible appetite-stimulating effect of progesterone in which EI appears to be lower. This suggests that it is perhaps animals. In humans, a review has summarized EI in relation not estrogen per se that mediates EI but that it might also be to menstrual cycle phases in 30 studies, which included a affected by progesterone. A certain increase in progesterone, total of 37 groups of women.31 Twenty-seven of the groups as occurs in the luteal phase, may somehow interact with demonstrated significantly higher EI in the luteal phase than estrogen and thus antagonize the metabolic effects of in the follicular phase. In seven groups no effect was seen, estrogen and thus increase EI. Further studies are required although a general tendency toward a higher luteal EI was to examine this hypothesis. Additionally, it would be observed. The remaining four groups had a higher EI in the interesting to investigate whether postmenopausal women, follicular phase than in the luteal phase, but these results and men (who have lower circulating levels of both estrogen were nonsignificant. and progesterone than premenopausal women), exhibit More recent studies support the findings of luteal similar patterns in EI in response to fluctuations in these hyperphagia,32–35 where women’s EI has been reported to hormones. increase with as much as 90–500 kcal/day compared to the Estrogens seem to possess potential for a beneficial effect follicular phase.33,34,36–46 Thus, most of the data from in women attempting to lose weight. However, it has been human studies also indicate that EI changes in response to speculated that women with a greater tendency toward changes in levels of ovarian hormones, and possibly to obesity are more sensitive to luteal hyperphagia and perhaps estrogens in particular.37,41,45,47 This is supported by data on do not respond adequately to this imbalance by lowering EI progesterone-treated ovariectomized rats, where progester- in the follicular phase when estrogen levels are elevated.19 one had no apparent effect on EI.26 This suggests that the Additionally, when progesterone is elevated in the luteal observations listed above may be due to an inverse, phase it has been shown to promote fat storage by decreasing noncausal association between the plasma concentration of lipoprotein lipase activity in the adipose tissue.51 This results estrogens and EI, rather than due to an appetite-stimulating in a decline in plasma triacylglycerols, and potentially in a effect of progesterone.24,30,48 In this context estradiol is concomitant increased desire for fat-rich foods.52 This is thought to be the crucial inhibitory signal linking the HPG inappropriate when trying to lose weight as high-fat foods axis to the neural control of feeding, and thereby inhibiting are associated with higher overall EI53 and may also impede EI by reducing the amount of food consumed at a single weight loss. meal.49 Ovariectomy on rats, which disrupts the normal The changes in appetite regulation that occur during the HPG function by preventing the secretion of estrogens and menstrual cycle have been suggested to be related to glucose nearly eliminating all estradiol from the circulation, has homeostasis, which may be an important determinant of been shown to increase EI, resulting in a 10–30% increase in eating behavior in premenopausal women. So far studies in body fat.50,51 This effect of estrogen in animals may also this area have yielded conflicting results. However, it has occur in humans. However, it is possible that progesterone, been proposed that insulin responsiveness is modified by sex perhaps without an apparent appetite-stimulating effect on hormones54,55 and that insulin sensitivity is lower in the its own, may still increase EI when interacting with estrogen. luteal phase than in the follicular phase.56–58 Table 1 presents reference values for normal ranges of It is well known that sex hormones also influence appetite estrogen and progesterone in premenopausal and postme- peptides such as ghrelin, leptin, glucagon-like-peptide 1, nopausal women and in men. It can be seen from Table 1 cholecystokinin and peptide YY.59 Studies of leptin show and Figure 1 that the ranges of estrogen (estradiol) in the gender difference with respect to levels of this peptide, also after controlling for body fat.60,61 However, within-gender difference is also seen as premenopausal women exhibit Table 1 Normal reference ranges for estrogen (estradiol) and progesterone higher levels than postmenopausal women.61 This suggests Early follicular Late follicular Luteal phase that cyclic changes in estrogen-responsive peptides such as phase phase leptin occur. However, we have been unable to find studies that have investigated whether sex hormones also interact Estrogen, estradiol (pmol/l) with appetite peptides to control changes in appetite over Premenopausal women 75–250 250–1500 250–750 Postmenopausal women o100 FFthe course of one menstrual cycle. Men o250 FF

Progesterone (nmol/l) Premenopausal women o2 o2 5–90 Postmenopausal women o2 FFMacronutrient intake, food cravings and the Men o2 FFpremenstrual syndrome

Endocrinology Reference Ranges, Royal Prince Alfred Hospital. Rodney Shearman Endocrinology Laboratory (www.gw.cs.nsw.gov.au/csls/RPAH/ Reports on macronutrient intake across the menstrual cycle endo/searchres.asp?TEST_GRP ¼ REPRODUCTIVE%20HORMONES). are inconsistent.31 Different studies have shown increases

International Journal of Obesity Menstrual cycle and energy balance L Davidsen et al 1780 during the luteal phase in carbohydrate,32,33,38,42,44,62–66 properties of a fat-rich food are also an element of the fat33,44,45,62,65 and protein consumption.44,62 Although re- experienced craving. ported independently of each other these increases may One study attempted to differentiate between the biologi- partly reflect a general increase in appetite rather than an cal and sensory properties of the satiation of nondrug increase in the intake of a particular macronutrient.31 cravings using chocolate.70 It seems that the urge to smoke Furthermore, methodological issues such as the ability of a cigarette is satisfied by the pharmacological effect of the test population to adequately differentiate between nicotine,76 whereas chocolate cravings do not seem to be carbohydrates and fat can be problematic as there are many satisfied by the pharmacological properties of chocolate, but ‘sweet-fat’-combination foods (for example, donuts). This more by sensory experiences involving aroma, sweetness and challenges the interpretation of data as it is impossible to texture.70 In this context a woman’s ability to correctly determine whether the consumption of something like a perceive sweet taste seems to play a primary role in donut is elicited by a craving for carbohydrate or fat, or determining her hedonic and other perceptual responses to perhaps even the combination of the two. substances such as chocolate.77 This perception of sweetness Nevertheless, the increase in carbohydrate consumption may vary across the menstrual cycle as sensory research has been referred to as carbohydrate craving (craving is suggests that women’s preferences for the sweet tastes and defined as an intense desire for a particular food or type of smells are increased in the luteal phase.46,63 This may be the food67). Retrospective data on food cravings provided by 758 reason for the higher frequency of craving premenstrually. women and 380 men showed that women especially craved Thus the reported changes in macronutrient intake during chocolate, and that they did so more frequently than men, the luteal phase may be elicited by a natural preference for and that they also preferred it to any other type of food.68 pleasant tasting, sweet, high-fat foods,19,78 which may be Other surveys also indicate chocolate as the most frequently enhanced premenstrually, thus possibly impeding adherence craved food among women,68–70 and there seems to be no to a weight management program. substitute that satisfies a chocolate craving.68 Interestingly, in one of the surveys 85% of women reported that they satisfied their cravings on more than 50% of occasions.68 Moreover, chocolate cravings seem to be more frequent in Resting metabolic rate and 24-h energy the luteal phase than at any other time of the cycle.71,72 This expenditure could result in an excessive intake of calories during this phase and consequently affect weight. A number of studies have indicated that daily energy Food cravings have been suggested to be influenced by the expenditure (EE) changes with phases of the menstrual premenstrual syndrome (PMS).73 This can interfere with cycle. Premenstrual increases in sleeping metabolic rate normal activities and/or interpersonal relationships, thus (SMR),79,80 basal metabolic rate (BMR)81–86 and 24-h distinguishing this syndrome from the premenstrual dis- EE79,87,88 have been reported. However, the increments in comfort experienced by most women. The prevalence of PMS EE in the luteal phase vary from one study to another. The is uncertain as various criteria are used to define the mean difference in SMR between the follicular and luteal condition. Prevalences from 5 to 60% have been reported, phase has been reported to be 6.1–7.7%,54,80 while mean with the highest rates seen in adolescent girls.74,75 In a study increases in 24-h EE of 2.5–11.5% have been shown.54,88 The of 313 women screened for PMS by questionnaires, women luteal increase in 24-h EE corresponds to an increase of with PMS exhibited a greater number of ‘episodes of eating’ 89–279 kcal. premenstrually than a control group.32 Furthermore, women Nevertheless, EE tends to vary substantially and mean with PMS experienced more severe cravings than women interindividual variation (CV) in BMR has been estimated to who reported no PMS symptoms.66,73 The etiology of PMS is 8–11.8%.89,90 More interestingly, the daily intraindividual unknown, but it is interesting to note that food can affect variation is wide ranging (1.7–10.4%, mean: 4.6%).89,91 mood, and it is well documented that mood changes are seen Some of the factors known to contribute to intraindividual premenstrually.31,66,73 In a study of 919 women, selected on variation in EE are stress, changes in nutritional status, the basis of their clear patterns of depression during three weight, physical activity and seasonal changes.92 Factors that menstrual cycles, it was observed that depression was influence interindividual variation include body size, age, positively related to food craving.31 gender, nutritional status and activities such as work, leisure It is possible that PMS and food craving share a common pursuits, fidgeting and exercising.92 Interindividual variation biochemical basis, in which giving into cravings actually in 24-h EE, adjusted for gender, is dependent on family traits, works to improve women’s mood. However, this has not yet because fat-free mass and fat mass are correlated within been established. families.93 Furthermore, it seems that both 24-h EE and SMR, Although the food consumed during the periods of independent of body composition and spontaneous physical cravings seems to be high in carbohydrates, it also tends to activity, are determined by plasma concentrations of the 33,40,44,45,62 be high in fat (for example, chocolate). As fat thyroid hormone triiodothyronine (T3) and norepinephr- provides flavor to foods, it is possible that the sensory ine.93 Thus, many factors seem to contribute to variations in

International Journal of Obesity Menstrual cycle and energy balance L Davidsen et al 1781 EE. However, when investigating a woman’s EE across one contain either a combination of synthetically derived menstrual cycle per se, some of the above-mentioned factors components of both estrogen (ethinylestradiol) and proges- such as size, gender, age and family traits remain constant terone (progestins), or progestins alone. The contraceptive and thus do not contribute to intraindividual variation. efficacy of these hormones lies in the suppression of 99 Instead, factors such as T3 and b-adrenergic hormones could ovulation and thickening of the cervical mucus, which more likely explain cyclic variations in EE if, for example, prevents pregnancy by preventing implantation of a ferti- diet and physical activity were to be held constant. One lized egg. These contraceptives interfere with the naturally study showed that the b-adrenergic support of resting energy occurring fluctuations in hormones in the menstrual cycle expenditure (REE) tended to be lower when suppressing sex and it can therefore be anticipated that this may exert an hormones by GnRH antagonist therapy suggesting sympa- effect upon energy balance, which may either benefit or thetic nervous system support of REE as a potential impede weight loss as the natural fluctuations in women’s mechanism mediating the reduction in REE with sex sex hormones are controlled. hormones suppression.94 However, to this date this possible To date only a few studies have investigated the effect of association has not been clarified. oral contraceptives on energy and macronutrient intake, and Nevertheless, it has been proposed that the reported the findings are contradictory. Significant increases in fat premenstrual increase in EE may be a result, at least in part, and EI have been reported in women using oral contra- of an increase in the concentration of progesterone.81,87,88 In ceptives compared to non-pill users.100,101 But there are also studies where increases in EE have been registered, a studies showing no differences in EI between pill users and concomitant increase in progesterone or its metabolic non-pill users.35,102,103 When interpreting the above-men- product in urine, pregnandiol (indicating an elevated level tioned results one should consider the formula of the oral of secreted progesterone), has been measured.87,88 Addition- contraceptives that are investigated in these studies. Com- ally, progesterone has been shown to be hyperthermic both bined and progestin-only pills as well as triphasic contra- in normal and in ovariectomized women,95,96 possibly ceptives are used. It is possible that the different formulas of mediated by a direct influence on the thermoregulatory oral contraceptives may result in diverse effects on EI. center in the hypothalamus.97 This suggests that progester- Moreover, the methods used for registering EI vary from one is a general metabolic stimulator. one study to another. More studies are warranted to clarify It has been suggested that changes in BMR may parallel this issue. changes in EI across the menstrual cycle as the two The effect of oral contraceptives on EE has also been parameters have shown similar patterns independently of studied. It appears that physiological variations in the each other.88 To investigate this, data on EI and EE need to be secretion of estrogens and progesterone affect EE, so obtained from the same group of women. To the authors’ exogenous administration of these hormones is likely to knowledge only one study has provided such data. This have an effect. One study showed that women who used oral study showed no correlation between EI and EE, although contraceptives had a significantly increased BMR (almost the changes in the two parameters across the menstrual cycle 5%) compared to non-pill users, even after adjustment for were of the same magnitude.35 It therefore remains un- differences in body weight and self-reported levels of known whether the changes in EI across the menstrual cycle physical activity.104 However, this was in contrast to a are driving changes in EE or vice versa. number of other studies, which reported no difference,35,100 The difference in methodologies used in the various or even a decrease in daily BMR102 and EE88 with the use of trials assessing these parameters probably contributes to oral contraceptives compared to no use. It is therefore not the divergence in results in this area. One factor that may be possible to draw any conclusions about the effect of oral a major bias is time and confirmation of ovulation as contraceptive agents on EE. the event separating the follicular and luteal phases. In the Body weight in relation to oral contraceptive use has also latter study ovulation was tested repeatedly over numerous been investigated.105–107 A recent review evaluated the cycles in 20 women. Only a few subjects had typical association between contraceptive use and changes in body 28-day cycles in which ovulation occurred close to day 14. weight by including randomized controlled trials that Ovulation ranged otherwise from day 10 to day 20. compared oral contraceptives with placebo or with another Relying on an average 28-day cycle may thus increase error oral contraceptive.106 Weight change comparisons during variance. 3–24 cycles of 47 different contraceptives and/or placebo pairs were represented. Most comparisons showed no substantial difference in body weight, which is supported by other studies.105,107 However, a minority of studies Hormonal contraceptives and energy balance reported a trend toward weight gain with oral contraceptive use compared to placebo. It was not possible to detect In the United States approximately 25% of all women using whether this was due to the dosage of estrogens or progestins contraception rely upon oral contraceptives for birth con- in the respective contraceptives, or due to other factors trol.98 Several types of oral contraceptives exist. These independent of the oral contraceptives.

International Journal of Obesity Menstrual cycle and energy balance L Davidsen et al 1782 Recently, injections of combined hormonal formulations dark chocolate may be associated with reduced risk of and progestins-only contraceptives have been introduced. A vascular diseases as its high content of cocoa contains recent study showed a significantly greater increase in body nutrients which have been shown to exert strong antiox- weight for women who received intramuscular injections of idant effects in vitro and in vivo in humans.112,113 Addition- Depo-Provera, a progestins-only contraceptive, for a period ally, it may be of interest to investigate whether the powerful of 30 months, compared to women using no hormonal taste of dark chocolate compared to light chocolate may contraception.108 Other studies support this finding.108–110 better satisfy a woman’s craving and thus preventing over- This may indicate a potential weight-inducing effect of consumption of chocolate. No data on this subject has yet progestins. However, it is uncertain whether the increase in been published. body weight was caused by the mode of administration It may be relevant to investigate which food items are (injection vs oral ingestion), which may alter the metabolic actually eaten to examine whether it is realistic to expect effects of this hormone; or whether the hormone itself, that craved foods (other than chocolate) can be successfully regardless of how it is administrated, is weight promoting. replaced by foods that contain less sugar and fat, while still Based on the presented data it seems that oral contra- satisfying women’s cravings. Women who suffer from PMS, ceptive use has no impact on body weight. The observed and thus from more severe symptoms of depression and food weight changes in the trials did not exceed those of the cravings and so on, may benefit from some kind of natural fluctuations in body weight which can occur during nutritional supplement/medication, as conscious changes a single day or across a menstrual cycle, for example, where in food intake alone may not be sufficient to relieve the women may experience a minor increase in body weight premenstrual discomfort. It is not the purpose of this review premenstrually and during the first days of the menstruation to evaluate possible treatments for PMS, but any supplement due to water retention.111 However, weight gain may be that can diminish premenstrual depression and thus im- promoted when transdermal contraceptives with specific prove mood would probably improve these women’s ad- progestin-only formulations are used. herence to a diet.114 Generally, our knowledge of the effect of hormonal contraceptives on energy balance is limited. Thus it remains unclear to what extent hormonal contraceptives that inter- Long-term weight management programs fere with hormones of the normal menstrual cycle may When attempting to develop a systematic weight manage- influence weight loss efforts. ment program based on menstrual phases, factors that may affect the chances of success must be considered. Pretreat- ment body weight is an important independent predictor of weight loss and slightly overweight women may not respond Implications for weight management programs as well to a weight management program as women who are obese.115 Nor do all women experience changes in cravings Energy intake and in food intake related to the menstrual cycle. This review It may be worth considering which stage of the menstrual addresses whether hormonal changes affect different com- cycle is appropriate for initiation of a weight loss regimen. It ponents of energy balance, such as food intake, but food appears that the body’s physiological needs for energy are intake can also affect hormones. Women who exhibit increased premenstrually, which gives rise to cravings and an cognitive restrained eating, for the purpose of either losing increased EI. One strategy may be to commence the diet on weight or controlling other factors, may experience irregula- the first day of menses (day 1), or in the late follicular phase rities in the menstrual cycle116 due to insufficient EI.117 They (days 5–11), when food cravings appear to be less intense, therefore cannot rely on a weight management program thereby making it easier to adapt to energy restriction and based on the assumption of a regular menstrual cycle. In establish a good basis for adherence to the diet. Carbo- investigations of the effects of the menstrual cycle on energy hydrate, fat and total EI could be moderately increased 5–8 balance components women have usually been kept on days before menstruation to meet the body’s increased energy balanced diets to prevent weight changes. However, energy demands, rather than rigidly adhering to a subopti- any given cyclic effect found under these circumstances mal caloric level. Cravings for carbohydrate should be (when energy balance is maintained) may change when alleviated mainly by foods such as fruit, which, apart from women adhere to an energy-deficient diet and consequently sugar, contain some vital nutritive elements. As chocolate is lose weight. This may induce an upregulation of appetite- frequently craved, and is seemingly irreplaceable, a small stimulating hormones, for example, ghrelin,118,119 along daily allowance of chocolate may improve adherence to the with an altered ratio between estrogens and progesterone, diet in the premenstrual period, preventing a sudden over- which may constitute a mechanism of counterregulation. It consumption of craved foods, such as chocolate, due to a may therefore be necessary to take into account the longer period of suppressing the craving. Dark chocolate changing metabolic state when dieting continues over a may be preferable as it contains the healthier monounsatu- longer period by readjusting diet composition, calorie rated oleic acid. Furthermore, moderate consumption of consumption and physical activity level.

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