Periodic cues, including scheduled exercise, social interactions, sleep habits, and feeding time, have been shown to alter the circadian system. A disruption in circadian rhythms has been shown to have negative effects on health. Frequent skin temperature measures have been shown to be a valid method of assessing circadian rhythm parameters. The purpose of this study was to determine group mean differences in temperature amplitude, stability and lag measures among groups of young men of varying (optimal, fair and poor) adiposities. The strength of the association among the temperatures parameters and measures of body composition, physical fitness and activity, nutritional intake, lipid concentrations, and sleep were also examined. Findings indicated that men with poor adiposity had significantly lower mean amplitude and stability than the optimal or fair groups; with no significant differences in lag among the groups. Factors including physical fitness, physical activity and late night eating contributed to the variance in amplitude; physical activity, time spent in moderate to vigorous activity, late night snacking, and fat mass to stability; and sleep hours and lipid ratios to lag. These findings contribute to the identification of targeted intervention strategies that may improve the circadian synchrony and health of young men.

Type 2 diabetes and cardiovascular disease (CVD), major public health concerns in Canada and worldwide, are the main outcomes of Metabolic Syndrome (MetS). MetS is a clustering of five chronic disease risk factors, including abdominal obesity, dyslipidemia (elevated triglycerides and reduced high-density lipoprotein cholesterol level), hypertension, and elevated fasting plasma glucose. Abdominal obesity and insulin resistance are the main factors contributing to development of MetS and thus CVD and diabetes. Further, dyslipidemia (specifically the total cholesterol/HDL-C ratio) is necessary to be monitored in people with these diseases or risk factors. The Canadian Health Measures Survey (CHMS) has direct health measurements that provide the opportunity to identify risk factors associated with chronic disease. Further, dietary intake has been assessed in CHMS, which can be utilized to evaluate the association with diseases and risk factors controlling for potential covariates. To examine the association between dietary intake with MetS and associated risks and diseases in Canadian adults and adolescents, data from CHMS cycle1, 2007-2009 (n=5604, aged 6-79 y) were used in which dietary intake was assessed using a semi-quantitative food frequency questionnaire. Frequency of food intake (times/day) and the distribution of individuals with and without disease or risk factors by socio-demographic characteristic was determined. Further, the association between dietary intake and each disease or risk factor was evaluated using logistic models. Data manipulation, cleaning, and creation of new variables were done using IBM SPSS statistics for windows, version 20. All statistical analyses were conducted by STATA/SE 11, StataCorp. As per Statistics Canada’s recommendation, data were weighted and bootstrapped using specific commands in STATA in order to be representative of the Canadian population. Physically active Canadians had significantly more milk and dairy product, fresh fruit and vegetable, and fruit and vegetable juice intake compared to inactive Canadians. Low-income households had significantly greater intakes of sugar-sweetened beverages (SSBs) and lower amounts of fresh fruit and vegetables than high-income households. Individuals with the lowest level of education had greatest potato and lowest fruit and vegetable juice intake. The prevalence of abdominal obesity (12-79 y), elevated TC/HDL-C ratio (20-79 y), MetS (12-79 y), and diabetes (20-79 y) was 35.7%, 20.5%, 18.3%, and 7.5%, respectively. The overall estimated percent risk of CVD over 10 years in adults aged 30-74 y was 8.66%. Abdominal obesity had the greatest contribution (~90%) to development of MetS in each age group compared to other components of MetS. Also, abdominal obesity was a strong significant predictor for development of other risk factors and chronic diseases including elevated TC/HDL-C ratio, diabetes, and CVD (OR: 6.12, CI: 2.68-13.96; OR: 2.25, CI: 1.24-4.06, OR: 1.4, CI: 1.06-1.87, respectively). High consumption of diet soft drink was associated with increased risk of abdominal obesity, Mets, diabetes, and elevated TC/HDL-C ratio. High consumption of fruit and vegetables and cereal was associated with decreased risk of CVD over 10 years whereas potato intake increased the risk. Intake of nuts appeared to be associated with reduction in the risk of MetS among Canadians. Dietary fat intake of one to less than 5 times/week was associated with increased risk of abdominal obesity in individuals over 40 years of age compared to 12-19 y individuals. Further, “ever drinking” alcohol compared to “never drinking” alcohol was associated with decreased risk of diabetes and elevated TC/HDL-C ratio. Low level of education contributed to development of abdominal obesity. Thus, abdominally obese individuals with specifically elevated TC/HDL-C ratio are at risk of developing MetS, CVD, and diabetes. They need to be educated with specific focus on physical activity, and greater intake of fruit and vegetables, nuts, and lower intake of dietary fat, diet soft drinks, and potato. Additionally, considering the social determinants which might contribute to increase the risk of chronic diseases or risk factors such as income, housing, accessibility to facilities in neighborhoods, school programs, or community programs is essential.

Despite inconsistent results in the literature, high protein diets are being promoted for the management of metabolic syndrome parameters primarily due to their proposed favorable effects on weight loss. Therefore, lean and fa/fa Zucker rats were given normal and high protein diets with varying protein sources for 12 weeks. A high protein diet with a mixture of animal and plant protein sources was the most effective for improving metabolic syndrome parameters, specifically insulin resistance and hepatic steatosis. A high protein soy diet was the second most effective diet, while a high protein casein diet demonstrated no benefits compared to the other two high protein diets and minimal benefits compared to a normal protein casein diet. Interestingly, high protein diets did not affect body weight regardless of protein source. These findings suggest that the source of protein within a high protein diet is critical for improving metabolic syndrome parameters and that improvements can be observed independent of weight loss.

No description available.

The prevalence of obesity in both the developed and developing world have increased, which leads to diverse health outcomes and is placing a heavy burden on the economy. Abdominal obesity proved to be one of the main features in predicting metabolic and cardiovascular disease (CVD) risk and may be the link that unifies the metabolic syndrome (MS) through pro-inflammatory pathways. While the pathogenesis of the MS and each of its components are complex and not well understood, abdominal obesity remains the mechanism that relates to increased lipolysis causing the liver to increase blood glucose and very low lipoprotein output. This in turns leads to raised blood glucose, triglycerides, low-density lipoprotein cholesterol (LDL-C), blood pressure and inflammatory markers (C-reactive protein, interleukin-6 and tumor necrosis factor-a) and decreased high-density lipoprotein cholesterol (HDL-C). Prevention of the metabolic syndrome and treatment of its main characteristics are now considered of utmost importance in order to combat the increased CVD risk and all-cause mortality. Decreasing sedentary behaviour through regular physical activity is a key element in successful treatment of obesity through an increase in energy expenditure, but the ability to decrease low-grade systemic inflammation may be an even greater outcome. Aims The aims of this study was firstly, to determine by means of a literature review, how obesity could be related to a state of chronic systemic inflammation (increased CRP and IL-6). Secondly to determine whether physical activity could serve as a suitable method to decrease inflammation associated with obesity and related disorders. Thirdly to determine if abdominal obesity is a predictor of the metabolic syndrome and CVD and finally, to determine if measures of obesity can predict risk for the metabolic syndrome and CVD risk. Methods For this review study, a computer-assisted literature search were utilized to identify research published between 1990 and 2005. the following databases were utilized for the search: NEXUS, Science Direct, PubMed and Medline. Keywords related to obesity (abdominal obesity, overweight), metabolic syndrome (insulin resistance syndrome, dysmetabolic syndrome, syndrome X), cardiovascular disease (coronary heart disease, coronary artery disease), cardiovascular risk factors (hypertension, dyslipidemia, diabetes mellitus, physical activity), inflammatory markers (CRP, IL-6, chronic low-grade inflammation) and physical activity (fitness, exercise and training) were included as part of the search, including the references identified by previous reviewers (not identified as part of the computerized literature search). Results and conclusions Several research studies concluded that obesity could be an inflammatory disorder due to low-grade systemic inflammation. Adipose tissue is known to be a sectretory organ producing cytokines, acute phase reactants and other circulating factors. The synthesis of adipose tissue TNF-a could induce the production of IL-6, CRP and other acute phase reactants. CRP is a acute phase reactant, synthesized primarily in hepatocytes and secreted by the liver in response to a variety of inflammatory cytokines of which IL-6 and TNF-a are mainly involved. CRP increases rapidly in response to trauma, inflammation and infection. Thus, enhanced levels of CRP can be used as a marker of inflammation. Several studies of large population cohorts provide evidence for an inverse, independent dose-response relation between plasma CRP concentration and level of physical activity in both men and women. Trends for decreased IL-6, TNF-a and CRP concentrations were linear with increasing amounts of reported exercise in most of the research studies, physical activity proved effective in lowering measures of adiposity (BMI, WHR, WC and percentage body fat) and obesity related inflammatory markers (CRP & IL-6). Thereby indicating a potential anti-inflammatory effect. In the studies reviewed in this article abdominal obesity is identified as a predictor and independent risk factor for CVD in both men and women. High levels of deep abdominal fat have also been correlated with components of the metabolic syndrome, glucose intolerance, hyperinsulinemia, hypertension, diabetes, increases in plasma triglyceride levels and a decrease in HDL-C levels (dyslipidemia) in many of the studies. Prospective epidemiological studies have revealed that abdominal obesity (determined by WC and WHR) conveys an independent prediction of CVD risk and is more relevant compared to general obesity (determined by BMI). Abdominal fat has been linked to metabolic risk factors like high systolic blood pressure, atherogenic dyslipidemia, with increased serum TG and decreased HDL-C, and glucose intolerance. Although magnetic resonance imaging (MRI) and computerized tomography (CT) have been used successfully in many studies to measure adipose compartments of the abdomen (subcutaneous and visceral fat), anthropometrical measures like WHR and WC have been proven to be an effective measure in predicting the metabolic syndrome. WC has also been included in the metabolic syndrome definitions of the WHO, ATP Ill and new IDF. / The prevalence of obesity in both the developed and developing world have increased, which leads to diverse health outcomes and is placing a heavy burden on the economy. Abdominal obesity proved to be one of the main features in predicting metabolic and cardiovascular disease (CVD) risk and may be the link that unifies the metabolic syndrome (MS) through pro-inflammatory pathways. While the pathogenesis of the MS and each of its components are complex and not well understood, abdominal obesity remains the mechanism that relates to increased lipolysis causing the liver to increase blood glucose and very low lipoprotein output. This in turns leads to raised blood glucose, triglycerides, low-density lipoprotein cholesterol (LDL-C), blood pressure and inflammatory markers (C-reactive protein, interleukin-6 and tumor necrosis factor-a) and decreased high-density lipoprotein cholesterol (HDL-C). Prevention of the metabolic syndrome and treatment of its main characteristics are now considered of utmost importance in order to combat the increased CVD risk and all-cause mortality. Decreasing sedentary behaviour through regular physical activity is a key element in successful treatment of obesity through an increase in energy expenditure, but the ability to decrease low-grade systemic inflammation may be an even greater outcome. Aims The aims of this study was firstly, to determine by means of a literature review, how obesity could be related to a state of chronic systemic inflammation (increased CRP and IL-6). Secondly to determine whether physical activity could serve as a suitable method to decrease inflammation associated with obesity and related disorders. Thirdly to determine if abdominal obesity is a predictor of the metabolic syndrome and CVD and finally, to determine if measures of obesity can predict risk for the metabolic syndrome and CVD risk. Methods For this review study, a computer-assisted literature search were utilized to identify research published between 1990 and 2005. the following databases were utilized for the search: NEXUS, Science Direct, PubMed and Medline. Keywords related to obesity (abdominal obesity, overweight), metabolic syndrome (insulin resistance syndrome, dysmetabolic syndrome, syndrome X), cardiovascular disease (coronary heart disease, coronary artery disease), cardiovascular risk factors (hypertension, dyslipidemia, diabetes mellitus, physical activity), inflammatory markers (CRP, IL-6, chronic low-grade inflammation) and physical activity (fitness, exercise and training) were included as part of the search, including the references identified by previous reviewers (not identified as part of the computerized literature search). Results and conclusions Several research studies concluded that obesity could be an inflammatory disorder due to low-grade systemic inflammation. Adipose tissue is known to be a sectretory organ producing cytokines, acute phase reactants and other circulating factors. The synthesis of adipose tissue TNF-a could induce the production of IL-6, CRP and other acute phase reactants. CRP is a acute phase reactant, synthesized primarily in hepatocytes and secreted by the liver in response to a variety of inflammatory cytokines of which IL-6 and TNF-a are mainly involved. CRP increases rapidly in response to trauma, inflammation and infection. Thus, enhanced levels of CRP can be used as a marker of inflammation. Several studies of large population cohorts provide evidence for an inverse, independent dose-response relation between plasma CRP concentration and level of physical activity in both men and women. Trends for decreased IL-6, TNF-a and CRP concentrations were linear with increasing amounts of reported exercise in most of the research studies, physical activity proved effective in lowering measures of adiposity (BMI, WHR, WC and percentage body fat) and obesity related inflammatory markers (CRP & IL-6). Thereby indicating a potential anti-inflammatory effect. In the studies reviewed in this article abdominal obesity is identified as a predictor and independent risk factor for CVD in both men and women. High levels of deep abdominal fat have also been correlated with components of the metabolic syndrome, glucose intolerance, hyperinsulinemia, hypertension, diabetes, increases in plasma triglyceride levels and a decrease in HDL-C levels (dyslipidemia) in many of the studies. Prospective epidemiological studies have revealed that abdominal obesity (determined by WC and WHR) conveys an independent prediction of CVD risk and is more relevant compared to general obesity (determined by BMI). Abdominal fat has been linked to metabolic risk factors like high systolic blood pressure, atherogenic dyslipidemia, with increased serum TG and decreased HDL-C, and glucose intolerance. Although magnetic resonance imaging (MRI) and computerized tomography (CT) have been used successfully in many studies to measure adipose compartments of the abdomen (subcutaneous and visceral fat), anthropometrical measures like WHR and WC have been proven to be an effective measure in predicting the metabolic syndrome. WC has also been included in the metabolic syndrome definitions of the WHO, ATP Ill and new IDF. / Thesis (M.A. (Human Movement Science))--North-West University, Potchefstroom Campus, 2006.

The aim of this study was to explore, from different perspectives, whether obesity related variables are associated with facets of psychological well-being, with a vision to future enhancement of health and the quality of life of people in the African context. This study was undertaken from the perspective of positive psychology and focused on the metabolic syndrome and obesity as biological facets. This research was conducted as part of the multidisciplinary POWIRS (Profiles of Obese Women with Insulin Resistance Syndrome) project. African (n=102) and Caucasian (1 15) women took part in a cross-sectional design. The thesis consists of 3 articles: I) Childhood relationships and bio-psycho-.gocia1 well-being in African women, 2) Psychological well-being and rhe metabolic syndrome in African and Caucasian women, and 3) Psychological wellbeing and (the absence of obesity in African and Caucasian women. In this study psychological well-being was conceptualized and operationalized by means of the General Health Questionnaire (GHQ); Sense of Coherence Scale (SOC-29); Affectometer 2 (AFM) (short form); Fortitude Questionnaire (FORQ); Cognitive Appraisa1 Questionnaire (CAQ); Psychological Well-being Scales (SPWB); Quality of Childhood Relationship Questionnaire (QCR); Satisfaction with Life Scale (SWLS) and the Jarel Spiritual Well-Being Scale (SWS-H). These scales were chosen to include hedonic as well as eudaimonic psychological well-being facets, but also an index of psychological symptoms. As far as possible, scales with acceptable psychometric properties as described in international as well as South African context were selected. The first article focused on whether African women with a recalled higher level of quality of childhood relationships mould differ significantly with regard to biological, psychological and social well-being from women with a recalled lower level of quality of childhood relationships. Body mass index (BMI) was used as objective measure of obesity to operationalize physical health. Findings were that the recalled quality of childhood relationships is linked with obesity and psycho-social well-being in this group of African women. The second article focused on psychological well-being and (the absence of) the metabolic syndrome (MS). It explored the possible association between comprehensive psychological well-being and MS in different cultural contexts, and explored whether African and Caucasian women without MS markers and those with MS differ on specific indices of psychological well-being. The criteria of the NCEP ATPIII mere implemented to determine markers of MS, and the absence of markers of MS was used as measure of physical health. Findings were that an association is found in Caucasian women between comprehensive psychological well-being and the absence of the metabolic syndrome, but not in the case of African women. Caucasian women without metabolic syndrome markers had significantly higher levels of psycho-social wellbeing than uomen with the metabolic syndrome. but a less apparent pattern of differences emerged for African women. MS markers for African women should be further explored. The third article explored facets of psychological well-being as predictors for (the absence of) obesity (measured by BMI and WHR) in African and Caucasian women, and whether similar or different psychological well-being facets will emerge as predictors of obesity in different cultural contexts. Obesity was operationalized in terms of waist-hip-ratio (WHR) and body-mass-index (BMI). The finding was that clusters of psychological well-being facets are practical significant predictors of obesity (measured by BMI and WHR) and that these clusters differ in some respects for African and Caucasian women. It was concluded that, firstly. findings support holistic conceptualizations of health such as proposed by the WHO (1999). Secondly, it may be worthwhile to include facets of psychological well-being in already existing intervention programmes. The development of strengths that focus on life skills and behaviours related to positive interpersonal relationships, optimistic cognitive attributional styles, finding a sense of purpose and meaningfulness in life, may be particularly beneficial. Sensitivity for cultural contexts is indicated. In view of the increase in the occurrence of obesity in childhood and adolescence it is recommended that educational training programmes should be implemented early in life in order to facilitate protective strengths and to promote bio-psycho-social health in individuals and communities. Advocacy for more attention to psycho-social and protective factors in public health is needed. / Thesis (Ph.D. (Psychology))--North-West University, Potchefstroom Campus, 2006.

Obesity is currently the most common and costly nutritional problem in developed countries and ten percent of the world's school-aged children are estimated to be overweight to some extent. Low-grade systemic inflammation is increasingly emerging as a significant component of the metabolic syndrome. Youth in lower income families are particularly vulnerable because of poor diet and limited opportunities for physical activity. In developing countries obesity among youth is rising among the urban poor, possibly due to their exposure to Westernised diets coinciding with a history of under-nutrition. The aim of this study was to assess the association between serum CRP and physical activity and to assess the association between serum CRP and body composition in black high-school children from a township in the North West Province (NWP), South Africa. Methods and results: The study group consisted of 193 school children between the ages 13 to 18 years (78 boys and 115 girls) residing in lkageng, the township outside of Potchefstroom in the North West Province, South Africa. Children were from a black ethnic group, living in a poor socioeconomic setting. Demographic and body composition measurements were taken and fasting blood samples were drawn for serum C-reactive protein (CRP) measurements. The difference between serum CRP of overfat versus girls with a normal fat percentage was non-significant (p = 0.46). Boys with body fat percentage >20% (n=16) had .a mean serum CRP of 1.42 2.16 mg/L and for boys with a normal fat percentage (n=53) mean serum CRP was 0.89 k 1.62 mg/L. The Mann-Whitney U-test for the difference between mean CRP of the two groups of boys was Z=1.39, p=0.16 (no significant difference), but with a trend of higher serum CRP concentration in the boys with higher % body fat. For the boys, the only positive partial correlation was between serum CRP and triceps skinfold (r=0.327, p=0.045). In the girls' group no statistically significant partial correlations were found between CRP and body composition variables. There was no significant difference between serum CRP concentrations of the three physical activity categories of girls. Interestingly, there was an inverse correlation between percentage body fat and fitness in the boys' group (r=-0.509 and p= 0.008). The difference in log CRP between activity groups showed a trend of lower serum CRP with higher physical activity in the girls. Conclusion: This study showed no statistically significant associations between serum CRP and body composition, except for the positive correlation between triceps skin fold and serum CRP in boys, or CRP and physical activity, but clear trends were noted of an inverse association between CRP and physical activity in the girls. / Thesis (M.Sc. (Nutrition))--North-West University, Potchefstroom Campus, 2007

Background: Breast and Gynecological cancers are a major public health problem. Smoking is associated with several chronic diseases including cancer. Other lifestyles of public health predispose many people to dyslipidemia, hypertension and obesity; risk factors for metabolic syndrome, and are associated with cancer. Objectives: The purpose of this study is to find if those who smoke, and have the metabolic syndrome, are more likely to have breast or gynecological cancers, and to find the distribution by education, having health insurance, race/ethnicity and socio-economic status. Methods: A case-control study of females aged 20 years and above who participated in the United States National Health and Nutrition Examination Survey (NHANES) 2001-2010. Results: Females who have smoked more than hundred cigarettes in life and still smoke; a) have a 42 percent less chance of having a breast cancer diagnosis (OR 0.58; 95% CI 0.36 – 0.93, p-value 0.025), and b) are 2.67 times as likely to report a cervical cancer diagnosis as females who have smoked less than hundred cigarettes in life (OR 2.67; 95% CI 1.72 – 4.13, p-value Conclusion: Smoking and metabolic syndrome are very important indicators of reproductive health and needs further study. Smoking cessation interventions should be an integral part of cervical cancer prevention programs especially targeted at younger females and females who live below the federal poverty level.

Emerging evidence suggests that vitamin D may be associated with type 2 diabetes (T2DM), however current data are inconsistent regarding metabolic disorders underlying T2DM. The objectives of this thesis were to investigate the association of vitamin D with the primary pathophysiological disorders of type 2 diabetes: namely insulin resistance (IR) and beta (β)-cell dysfunction, and the metabolic syndrome (MetS). All studies included individuals participating in the PROspective Metabolism and ISlet cell Evaluation (PROMISE) cohort study, comprising 712 subjects 30 years and older, and at risk of T2DM at baseline. Serum 25-hydroxyvitamin D [25(OH)D] was measured to assess vitamin D nutritional status. Validated oral glucose tolerance test derived indices for IR and β-cell function were calculated. In the first cross-sectional study, multivariate linear regression analyses indicated a significant inverse association of serum 25(OH)D with IR (β=-0.003, p=0.007) and a significant positive association of 25(OH)D with β-cell function (β=0.004, p=0.03) at the baseline PROMISE clinic visit (n=712). In another cross-sectional study also conducted using data from the baseline PROMISE clinic visit, higher 25(OH)D was found to be significantly associated with a reduced presence of the MetS after multivariate adjustment (OR=0.76, 95% CI 0.62-0.93). Low serum 25(OH)D was also significantly associated with various MetS components. In light of the findings in the first cross-sectional study, the third study examined prospective associations of baseline 25(OH)D with 3-year follow-up IR and β-cell function (n=489). Although baseline 25(OH)D was not significantly associated with follow-up IR, a significant positive association of baseline 25(OH)D with β-cell function at follow-up was observed (β=0.005, p=0.015). Lastly, in a longitudinal substudy (n=127), seasonal changes in 25(OH)D over 2.5 years did not significantly affect changes in IR and β-cell function. In conclusion, results indicated that baseline serum 25(OH)D was cross-sectionally related to IR, β-cell function and the MetS, and was prospectively related to β-cell function at the 3-year follow-up. In addition, seasonal changes in 25(OH)D do not adversely affect IR and β-cell function over time. These findings suggest a potential role for higher 25(OH)D levels in reducing diabetes risk, although additional longitudinal studies are warranted.

Emerging evidence suggests that vitamin D may be associated with type 2 diabetes (T2DM), however current data are inconsistent regarding metabolic disorders underlying T2DM. The objectives of this thesis were to investigate the association of vitamin D with the primary pathophysiological disorders of type 2 diabetes: namely insulin resistance (IR) and beta (β)-cell dysfunction, and the metabolic syndrome (MetS). All studies included individuals participating in the PROspective Metabolism and ISlet cell Evaluation (PROMISE) cohort study, comprising 712 subjects 30 years and older, and at risk of T2DM at baseline. Serum 25-hydroxyvitamin D [25(OH)D] was measured to assess vitamin D nutritional status. Validated oral glucose tolerance test derived indices for IR and β-cell function were calculated. In the first cross-sectional study, multivariate linear regression analyses indicated a significant inverse association of serum 25(OH)D with IR (β=-0.003, p=0.007) and a significant positive association of 25(OH)D with β-cell function (β=0.004, p=0.03) at the baseline PROMISE clinic visit (n=712). In another cross-sectional study also conducted using data from the baseline PROMISE clinic visit, higher 25(OH)D was found to be significantly associated with a reduced presence of the MetS after multivariate adjustment (OR=0.76, 95% CI 0.62-0.93). Low serum 25(OH)D was also significantly associated with various MetS components. In light of the findings in the first cross-sectional study, the third study examined prospective associations of baseline 25(OH)D with 3-year follow-up IR and β-cell function (n=489). Although baseline 25(OH)D was not significantly associated with follow-up IR, a significant positive association of baseline 25(OH)D with β-cell function at follow-up was observed (β=0.005, p=0.015). Lastly, in a longitudinal substudy (n=127), seasonal changes in 25(OH)D over 2.5 years did not significantly affect changes in IR and β-cell function. In conclusion, results indicated that baseline serum 25(OH)D was cross-sectionally related to IR, β-cell function and the MetS, and was prospectively related to β-cell function at the 3-year follow-up. In addition, seasonal changes in 25(OH)D do not adversely affect IR and β-cell function over time. These findings suggest a potential role for higher 25(OH)D levels in reducing diabetes risk, although additional longitudinal studies are warranted.