Dincolo de post: beneficiile metabolice ale postului din Ramadan pentru femeile musulmane

Ramadan intermittent fasting: definition, practice and physiological mechanisms

Ramadan intermittent fasting (RIF) involves approximately 12-18 hours of daily complete abstinence from food, water and all oral intake from dawn (Fajr) to sunset (Maghrib), sustained across the 29-30-day month of Ramadan^(6,18). The fasting window varies geographically and seasonally, ranging from approximately 11 hours in equatorial regions to over 18 hours at higher latitudes during summer months. For Muslim women, Islamic jurisprudence provides exemptions during menstruation, pregnancy, breastfeeding and illness, with missed fasting days to be compensated after Ramadan⁽¹⁴⁾. Never­theless, a substantial proportion of healthy pre- and postmenopausal women voluntarily observe RIF, often adapting to a biphasic eating pattern consisting of Suhoor (pre-dawn meal) and Iftar (post-sunset meal), with optional nocturnal snacking⁽³⁾.

Dietary patterns during non-fasting hours are heavily shaped by cultural traditions, with Iftar typically initiated with dates and water, followed by soups, lentils, bread and high-glycemic index carbohydrates^(12,20). Despite ad libitum eating during permitted hours, several studies report a net caloric deficit of approximately 300-900 kJ/day in some populations during Ramadan, primarily attributable to compressed eating windows and reduced meal frequency rather than intentional caloric restriction^(19,23). However, this deficit is not universal; energy intake can remain stable or increase in populations with calorie-dense traditional foods or extended nocturnal eating, complicating cross-study comparisons^(12,21).

Sleep architecture is also substantially disrupted during Ramadan, with delayed sleep onset, reduced total sleep time and fragmented sleep patterns reported across multiple studies⁽³⁾. These sleep shifts interact with circadian rhythm alterations, influencing hormonal regulation, appetite signaling and metabolic outcomes independently of fasting per se⁽³⁾.

Physiological mechanisms of RIF

From a metabolic standpoint, RIF induces a progressive shift from glucose oxidation to fatty acid oxidation and ketone body production after approximately 8-12 hours of fasting^(4,15). Glycogen stores are depleted, and hepatic gluconeogenesis is upregulated to maintain euglycemia, while rising plasma free fatty acids and ketone bodies serve as alternative substrates for peripheral tissues and the brain⁽¹⁵⁾. This metabolic switch is central to many of the proposed health benefits of intermittent fasting more broadly, and RIF appears to recapitulate similar physiological transitions⁽⁴⁾.

Ramadan intermittent fasting also activates autophagy, a cellular housekeeping process involving the degradation and recycling of damaged organelles and proteins through nutrient-sensing pathways, including AMPK activation and mTORC1 inhibition^(13,15). Autophagic flux has been proposed as a mechanism underlying the anti-inflammatory and cardiometabolic benefits observed with fasting, although direct human evidence during RIF remains limited⁽¹³⁾.

Hormonally, Ramadan intermittent fasting produces consistent reductions in fasting insulin levels, reflecting improved pancreatic beta-cell rest and reduced hepatic insulin demand during the fasting window^(18,25). Leptin, an adipokine that signals satiety and regulates long-term energy balance, is significantly reduced during Ramadan in overweight and obese women, potentially reflecting reduced adipose tissue mass or altered nocturnal secretion patterns^(3,5). Conversely, ghrelin, the primary orexigenic hormone, exhibits an initial rise during the early days of Ramadan fasting, consistent with hunger adaptation, although the levels tend to normalize as the month progresses⁽⁵⁾.

Sex-specific considerations: estrogen, menstrual phase and menopause

Women represent a biologically distinct subgroup in RIF research, yet they remain underrepresented in mechanistic studies. Estrogen exerts pleiotropic effects on metabolism, including upregulation of fat oxidation, modulation of insulin sensitivity and protection against visceral fat accumulation⁽¹⁶⁾. Across the menstrual cycle, estrogen and progesterone fluctuations influence substrate utilization, appetite regulation and thermogenesis, suggesting that metabolic responses to RIF may differ between follicular and luteal phases^(10,16).

In premenopausal women, several studies have documented adaptive fat mobilization during the Ramadan intermittent fasting, with preferential loss of subcutaneous adipose tissue, while lean mass is preserved, a pattern attributed in part to estrogen-mediated lipolytic signaling^(12,22). Postmenopausal women, characterized by estrogen deficiency and a shift toward android fat distribution, may exhibit attenuated lipolytic responses but potentially greater improvements in insulin resistance and lipid profiles, given their higher baseline cardiometabolic risk⁽⁹⁾. Direct comparative data between pre- and postmenopausal women during RIF remain scarce, representing a significant gap in the literature.

Body weight, BMI and anthropometric outcomes of RIF

Ramadan intermittent fasting produces consistent and statistically significant reductions in body weight and Body Mass Index (BMI) across diverse populations, representing one of the most robustly documented outcomes in the intermittent fasting literature. A landmark meta-analysis by Correia et al. (2021), with pooling data from 35 studies, reported a mean weight reduction of approximately 1.24 kg (95% CI; -1.60 to -0.88 kg) and a BMI decrease of approximately 0.5-1 kg/m², with findings consistent across geographic regions, though effect sizes varied meaningfully by ethnicity. Asian participants demonstrated greater weight loss (-1.56 kg) compared to African and European counterparts (-0.64 kg), a disparity hypothesized to reflect the differences in baseline dietary patterns, fasting duration, ambient temperature, cultural food practices and pre-Ramadan metabolic status^(6,23). These ethnic differences highlight the importance of contextualizing RIF outcomes within sociocultural and environmental frameworks rather than applying universal estimates.

Sex-stratified analyses further reveal meaningful differences in weight loss magnitude. Women achieve a mean weight reduction of approximately 0.92 kg during Ramadan compared to 1.51 kg in men, a gap attributable in part to the shorter cumulative fasting exposure among women due to menstrual exemptions, which may reduce total fasting by 4-7 days across the month^(6,22). Additionally, hormonal differences – particularly the role of estrogen in preserving fat stores and attenuating lipolysis relative to men – may contribute to the comparatively modest weight reduction observed in women⁽¹⁶⁾. Despite this, even modest weight reductions in the range of 0.9-1 kg are clinically meaningful when sustained, given their downstream effects on blood pressure, insulin sensitivity and lipid profiles⁽¹¹⁾.

Waist circumference and body fat percentage represent complementary anthropometric outcomes that extend beyond weight alone. RIF-induced reductions in waist circumference of approximately 1.5-3 cm have been reported across multiple studies, with visceral fat loss proposed as a primary driver of cardiometabolic benefit^(12,19). These reductions are particularly clinically significant, given that central adiposity is a stronger predictor of cardiovascular and metabolic disease risk than total body weight⁽¹¹⁾.

Menopausal status and anthropometric responses: evidence from a Saudi cohort

Subgroup data stratified by menopausal status remain scarce, but offer important mechanistic insights. A Saudi cohort study (n=62 women), directly comparing premenopausal (PRE-M; n=31) and postmenopausal (POST-M; n=31) women across Ramadan, demonstrated significant anthropometric improvements in both groups (Table 1)⁽²⁾. In PRE-M women, BMI decreased from 25.3±4.7 to 24.6±4.6 kg/m² (p<0.001), waist circumference from 82.5±13.5 to 80.1±13.2 cm, and body fat percentage decreased from 36.9±7.8% to 35.7±7.9%. POST-M women demonstrated comparable reductions, with BMI declining from 27.9±4.2 to 27.1±4.1 kg/m², suggesting that RIF-induced fat mobilization persists despite the estrogen-deficient state characteristic of menopause⁽²⁾.

The parallel magnitude of response across menopausal groups is notable. Postmenopausal women typically exhibit blunted lipolytic responses due to reduced estrogen-mediated adipose tissue sensitivity and a predominance of visceral over subcutaneous fat deposition^(7,16). The observed BMI and waist reductions in this group therefore suggest that the caloric deficit and hormonal shifts induced by RIF, including reduced insulin and leptin, may be sufficient to overcome the lipolytic resistance associated with menopause, at least transiently⁽⁹⁾. Cortisol dynamics during prolonged daily fasting may also contribute, with RIF-associated cortisol elevation potentially amplifying lipolysis in both menopausal subgroups, although this requires further investigation⁽³⁾.

Post-Ramadan weight regain and sustainability

A critical limitation of RIF as a weight management strategy is the tendency toward post-Ramadan weight regain. Pooled data indicate a mean rebound of approximately 0.72 kg within 4-6 weeks following Ramadan cessation, largely attributable to the restoration of habitual ad libitum eating patterns, resumption of regular sleep schedules and the removal of the religious and social structure that enforces fasting adherence^(6,23). This regain pattern mirrors the one observed in other time-restricted and caloric restriction interventions, where the absence of sustained behavioral change or structured follow-up invariably attenuates the initial anthropometric gains⁽²⁶⁾.

From a clinical perspective, the transient nature of RIF-induced weight loss underscores the need for post-Ramadan dietary counseling, physical activity promotion and habit formation strategies to consolidate gains beyond the fasting month^(9,12). Longitudinal studies tracking women across multiple consecutive Ramadan cycles are lacking, but would be valuable in determining whether repeated annual RIF produces cumulative or sustained cardiometabolic benefit beyond a single fasting episode.

Cardiometabolic and lipid effects of RIF

Ramadan intermittent fasting produces clinically meaningful improvements in lipid profiles, with meta-analytic evidence consistently documenting reductions in serum triglycerides of approximately 15-20% (p=0.002) and increases in HDL-cholesterol of 5-10% (p=0.027)⁽¹²⁾. These changes are particularly significant, given that dyslipidemia characterized by elevated triglycerides and low HDL is highly prevalent among postmenopausal women, driven by the loss of estrogen-mediated hepatic lipoprotein regulation and increased visceral adiposity^(7,16). Notably, lipid improvements appear more pronounced in premenopausal women, likely reflecting the synergistic interaction between estrogen-enhanced lipoprotein lipase activity and the metabolic shifts induced by prolonged daily fasting⁽²²⁾. With respect to blood pressure, systolic values remain largely unchanged across studies, while diastolic blood pressure demonstrates a more notable decline in postmenopausal women, with one study reporting a statistically significant menopausal-status interaction effect (p=0.021), suggesting that the vasodilatory benefits of improved insulin sensitivity and reduced sympathetic tone during fasting may be amplified in the estrogen-deficient state^(2,18). Broader meta-analytic comparisons indicate that the overall cardiometabolic gains from RIF are small but statistically significant, and broadly comparable to those achieved through non-Ramadan intermittent fasting protocols, with pooled weight differences of approximately -0.341 kg (p=0.006) between RIF and non-Ramadan IF groups, suggesting that fasting structure and duration rather than religious context alone are the primary determinants of metabolic benefit⁽⁶⁾.

Insulin sensitivity, glucose regulation and PCOS in women

Beyond lipid and anthropometric outcomes, Ramadan intermittent fasting exerts meaningful effects on insulin sensitivity and glycemic regulation, mediated primarily through the reduction of chronic hyperinsulinemia associated with frequent feeding and the extension of overnight fasting duration^(15,18). By compressing caloric intake into a restricted nocturnal window, RIF reduces the total daily insulin secretory burden, enhances hepatic insulin clearance, and promotes GLUT4 upregulation in peripheral tissues, collectively improving insulin sensitivity indices over the fasting month^(4,12). However, glucose dynamics during RIF are not uniformly favorable; transient postprandial hyperglycemia can occur at Iftar due to the rapid ingestion of high-glycemic foods such as dates, white rice and sweetened beverages, while the pre-dawn cortisol surge, a physiological component of the hypothalamic-pituitary-adrenal awakening response, can elevate fasting glucose in the hours before Fajr⁽¹²⁾. The consumption of a balanced Suhoor meal, rich in complex carbohydrates, protein and fiber, has been shown to attenuate this cortisol-mediated glucose rise, blunting the hepatic glucose output that would otherwise occur in the extended pre-dawn fasting period^(12,20). For women with polycystic ovary syndrome (PCOS), a condition characterized by insulin resistance, hyperandrogenemia and menstrual irregularity, RIF may offer particular therapeutic value. A review by Waqar et al. (2022) noted emerging evidence that Ramadan fasting is associated with improvements in menstrual cycle regularity in women with PCOS, plausibly attributable to RIF-induced reductions in fasting insulin, which in turn lower luteinizing hormone (LH) pulse frequency and ovarian androgen synthesis, thereby partially restoring hypothalamic-pituitary-ovarian axis function^(22,27). While these findings are preliminary and derived largely from observational data, they highlight the potential for RIF to serve as an accessible, low-cost adjunct to conventional PCOS management in Muslim women who already observe Ramadan.

Inflammatory, oxidative stress and hormonal effects of RIF in women

Ramadan intermittent fasting exerts significant anti-inflammatory and antioxidant effects that are particularly relevant for women, who carry a higher baseline inflammatory burden due to adipokine dysregulation and, in post-menopausal women, the loss of estrogen’s endogenous anti-inflammatory activity^(9,16). Mechanistically, prolonged daily fasting activates the Nrf2 (nuclear factor erythroid 2-related factor 2) transcriptional pathway, upregulating endogenous antioxidant enzyme systems, including superoxide dismutase (SOD) and glutathione peroxidase (GPx), both of which revealed significant increases (p=0.016-0.05) across pre- and postmenopausal women in cohort data, with levels inversely correlated to fat mass^(2,17). Concurrently, the proinflammatory cytokine TNF-a declined more substantially in premenopausal women (p=0.021), while the anti-inflammatory cytokine IL-10 increased in both groups, reflecting a shift toward an immunologically favorable level during RIF⁽¹⁷⁾. C-reactive protein (CRP) positivity, a clinical marker of systemic low-grade inflammation, was halved in premenopausal participants (declining from 6.45% to 3.23%), consistent with the broader literature demonstrating that caloric restriction and time-restricted eating attenuate hepatic acute-phase protein synthesis^(12,18). These anti-inflammatory gains are of particular clinical relevance in the context of postmenopausal cardiovascular and metabolic disease risk, where chronic low-grade inflammation is a key pathophysiological driver⁽¹¹⁾.

Hormonal rebalancing, menstrual effects and PCOS

Ramadan intermittent fasting produces divergent but potentially complementary hormonal effects across menopausal strata. In premenopausal women, estrogen levels declined modestly during Ramadan (p<0.05), consistent with the negative energy balance and hypothalamic-pituitary-gonadal axis sensitivity to caloric restriction, while in postmenopausal women estrogen exhibited a paradoxical rise (p=0.01 interaction), attributable to increased peripheral aromatization of androgens within the adipose tissue that is mobilized during fasting-induced lipolysis^(8,16). The positive correlation between fat mass reduction and estrogen change in postmenopausal women supports this adipose-estrogen hypothesis, and progesterone levels remained stable across both groups, indicating that RIF does not substantially perturb the luteal phase hormonal environment in healthy women⁽²⁾. Menstrual cycle disruptions most commonly cycle lengthening or delayed ovulation are reported in approximately 20-30% of premenopausal women fasting during Ramadan, with dehydration, sleep fragmentation and circadian rhythm disruption identified as primary contributing mechanisms⁽²⁷⁾. Importantly, these irregularities are transient and resolve within one to two cycles following Ramadan cessation, with no documented long-term effects on fertility or reproductive endocrine function in otherwise healthy women⁽²⁷⁾. Clinical guidance consistently recommends prioritizing hydration at Iftar and Suhoor, consuming electrolyte-rich foods and maintaining adequate micronutrient intake particularly iron, given menstrual blood losses to support cycle stability and minimize fasting-related hormonal perturbation^(20,27). For women with PCOS, as noted in the preceding section, RIF may additionally offer cycle-regularizing benefits via reductions in fasting insulin and downstream suppression of ovarian androgen excess^(22,27).

Sex-specific physiological advantages and comparison with non-Ramadan intermittent fasting

Women’s characteristically higher baseline body fat percentage confers a physiological advantage during RIF by providing a more abundant lipid substrate for beta-oxidation, enabling sustained energy provision throughout the fasting window, without recourse to protein catabolism^(9,16).In postmenopausal women, where estrogen deficiency drives a preferential shift toward visceral adiposity and accelerated loss of skeletal muscle mass (sarcopenic obesity), the muscle-sparing metabolic adaptations of RIF are particularly valuable, such as the amplified improvement in blood pressure and lipid parameters observed in this group relative to pre-menopausal counterparts^(2,7). Comparative meta-analy­ses indicate that non-Ramadan intermittent fasting protocols, particularly time-restricted feeding (TRF), produce modestly larger reductions in fat mass (FM: -0.447 kg; p<0.001) and FFM gains compared to RIF, likely reflecting the greater dietary control, longer intervention durations and the absence of Ramadan-specific confounders such as sleep disruption and high-glycemic Iftar foods in TRF trials^(6,23). Nevertheless, the overall cardiometabolic trajectory of RIF in women is broadly comparable to non-Ramadan IF, supporting its utility as a structured, culturally embedded fasting framework⁽⁶⁾.

Risks, safety considerations and vulnerable subgroups

Despite its benefits, Ramadan intermittent fasting carries several risks that warrant clinical attention, particularly in women. Fluid restriction during daylight hours, often exceeding 14-16 hours during summer months at higher latitudes, creates a significant daily dehydration burden, with women generally more susceptible than men due to lower absolute body water volume and higher rates of insensible perspiration relative to body surface area⁽²⁴⁾. In hot climates, this dehydration risk is compounded by heat-related fluid losses, and may precipitate headaches, fatigue, impaired cognitive performance and, in severe cases, hyponatremia, particularly in women with low dietary sodium intake during Iftar⁽¹²⁾. Hypoglycemia during the extended fasting window is uncommon in non-diabetic women but warrants monitoring in older postmenopausal women with borderline impaired fasting glucose, given the additive effects of cortisol-mediated glucose dysregulation and reduced counter-regulatory hormone efficiency with ageing^(3,18). Post-Ramadan weight regain estimated at approximately 0.72 kg on average remains a consistent limitation, underscoring the need for sustained behavioral strategies beyond the fasting month, as detailed in earlier sections⁽²³⁾. Appropriately, Islamic jurisprudence provides categorical exemptions from fasting for pregnant, breastfeeding and acutely ill women; meta-analyses and clinical guidelines uniformly exclude these subgroups from RIF recommendations, reflecting both ethical considerations and the established evidence of adverse perinatal outcomes associated with fasting-induced maternal nutritional restriction (Table 2)^(23,27).

Comparative evidence from meta-analyses: RIF versus non-Ramadan intermittent fasting

When compared head-to-head with non-Ramadan intermittent fasting protocols, Ramadan intermittent fasting consistently demonstrates somewhat attenuated reductions in fat mass and BMI. Pooled meta-analytic data indicate that non-Ramadan IF produces a standardized mean difference in BMI of approximately -0.699 (p<0.001), exceeding the modest but significant weight reductions of -1.24 kg observed across the 35-study Ramadan meta-analysis reported by Correia et al. (2021), with RIF gains largely subject to post-Ramadan regain, as discussed previously. These differences are attributable to several structural features of non-Ramadan IF protocols: they typically involve greater dietary control, longer intervention periods, explicit caloric targets, and the absence of culturally driven high-glycemic Iftar eating patterns that can blunt the metabolic benefits of the fasting window^(6,23). Non-Ramadan IF also yields larger fat-free mass preservation, with time-restricted feeding studies reporting FFM gains of approximately +0.306 kg (p=0.001) compared to the more variable FFM responses seen in RIF⁽⁶⁾. Nevertheless, a critical distinguishing advantage of RIF is adherence: the religious, communal and spiritual dimensions of Ramadan create a unique powerful motivational infrastructure that sustains fasting behavior across the full 29-30-day period in ways that secular dietary interventions rarely achieve, particularly among Muslim women for whom Ramadan observance carries profound personal and cultural significance^(2,22). Taken together, the evidence suggests that, while non-Ramadan IF may produce superior body composition outcomes under controlled conditions, RIF offers a pragmatic, population-accessible and culturally reinforced pathway to cardiometabolic benefit, particularly when complemented by dietary quality improvements during non-fasting hours.

Long-term health implications and research gaps

Emerging longitudinal evidence suggests that sustained Ramadan fasting observed across multiple consecutive years may confer cumulative cardiovascular and metabolic benefits beyond those detectable within a single fasting cycle. Rouhani and Azadbakht (2014) noted in their comprehensive review that regular long-term participation in Ramadan fasting is associated with more favorable lipid profiles, lower rates of obesity and reduced inflammatory marker burden compared to non-fasting Muslim counterparts, outcomes proposed to reflect the compounding effects of annual autophagy activation, recurrent reductions in visceral adiposity and repeated improvements in insulin sensitivity. These long-term protective signals are particularly meaningful for Muslim women residing in high-obesity regions, including the Gulf Cooperation Council states, South Asia and North Africa, where the prevalence of metabolic syndrome, type 2 diabetes and cardiovascular disease is disproportionately elevated and where RIF represents a culturally embedded, cost-free and annually recurring health intervention^(12,22). However, the evidence base remains constrained by a near-complete absence of well-designed randomized controlled trials with extended follow-up, consistent outcome reporting and adequate representation of women across menopausal strata and ethnically diverse populations^(2,6). Future research priorities should include multi-year longitudinal cohort studies in wo­men, RCTs comparing RIF with matched non-Ramadan IF controls in female-only samples, and mechanistic studies examining autophagy flux, telomere biology and epigenetic ageing markers as potential mediators of RIF’s long-term health effects.

Practical recommendations for optimizing RIF in women

The translation of RIF’s health benefits into clinical practice requires individualized guidance that accounts for the unique physiological demands of fasting Muslim women. To stabilize postprandial glucose and attenuate the Iftar glycemic spike, Suhoor and Iftar meals should be structured around slow-digesting complex carbohydrates, lean protein sources such as eggs, legumes and yogurt, and dietary fiber from vegetables and nuts, a pattern shown to blunt cortisol-mediated hepatic glucose output and extend satiety across the fasting window^(12,20). Adequate hydration is a clinical priority, with a target of 2-3 liters of water and electrolyte-containing fluids consumed between Iftar and Suhoor to offset the dehydration burden of prolonged fluid restriction, particularly in women at risk of menstrual cycle disruption, headaches or reduced cognitive performance⁽²⁷⁾. Moderate-intensity physical activity, such as walking, resistance training or yoga performed in the evening hours following Iftar, represents the optimal window for exercise during Ramadan, enabling fat-free mass preservation and cardiovascular conditioning without the hypoglycemic and dehydration risks associated with daytime activity⁽⁶⁾. Clinical monitoring should prioritize menstrual cycle tracking in premenopausal women, blood pressure surveillance in postmenopausal women and proactive consultation for those managing comorbidities, including type 2 diabetes, hypertension or thyroid disorders, for whom RIF-specific medication adjustment protocols should be discussed with a healthcare provider prior to Ramadan commencement^(2,27). Integrated with these lifestyle strategies, RIF holds genuine potential as a platform for sustained metabolic resilience in Muslim women, one that is most durably effective when its annual recurrence is used as a springboard for year-round dietary and behavioral consolidation rather than treated as an isolated month-long intervention^(12,22).

Conclusions

Ramadan intermittent fasting represents a uniquely positioned health intervention for Muslim women, one grounded in religious obligation, yet carrying measurable and increasingly well-documented cardiometabolic benefits. Across the evidence reviewed, Ramadan intermittent fasting consistently produces significant reductions in body weight, BMI, waist circumference, triglycerides and inflammatory markers, alongside improvements in HDL-cholesterol, insulin sensitivity and antioxidant enzyme activity, with effects observed across both pre- and postmenopausal strata. The hormonal landscape of women, shaped by estrogen fluctuation, menstrual cyclicity and menopausal transition, modulates the magnitude and character of these responses in ways that are physiologically meaningful and clinically instructive, underscoring the inadequacy of applying sex-neutral findings to female populations. While non-Ramadan intermittent fasting protocols achieve modestly superior body composition outcomes under controlled conditions, RIF’s unparalleled adherence rates, driven by spiritual motivation, communal reinforcement and cultural identity, represent a translational advantage that secular dietary interventions rarely replicate. Nevertheless, the evidence base carries important limitations. The predominance of short-term, observational and methodologically heterogeneous studies, the underrepresentation of women in sex-stratified analyses and the near-complete absence of multi-year longitudinal data constrain the strength of conclusions that can currently be drawn. Post-Ramadan weight regain, dehydration risk, transient menstrual disruption and the glycemic challenges of culturally traditional Iftar diets represent practical barriers that require targeted clinical guidance rather than dismissal. Future research must prioritize well-designed RCTs in female-only cohorts, multiethnic longitudinal studies and mechanistic investigations of autophagy, epigenetic ageing and reproductive endocrine function across repeated Ramadan cycles.

Autor corespondent:   Faiz M.M.T. Marikar E-mail: faiz@kdu.ac.lk

CONFLICT OF INTEREST: none declared.

FINANCIAL SUPPORT: none declared.

This work is permanently accessible online free of charge and published under the CC-BY.