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The aim of this study was to assess the relationship between obesity and vitamin D status cross-sectionally, the relationship between obesity and the incidence of hypovitaminosis D prospectively and inversely the relationship between vitamin D status and incidence of obesity in a population-based cohort study in Spain. At baseline (1996-1998), 1226 subjects were evaluated and follow-up assessments were performed in 2002-2004 and 2005-2007, participants undergoing an interview and clinical examination with an oral glucose tolerance test. At the second visit, 25-hydroxyvitamin D and intact parathyroid hormone concentrations were also measured. Prevalence of obesity at the three visits was 28.1, 36.2 and 39.5%, respectively. The prevalence of vitamin D deficiency (25-hydroxyvitamin D ≤ 20 ng/ml (≤ 50 nmol/l)) was 34.7%. Neither obesity at baseline (OR=0.98, 95% CI: 0.69-1.40, P=0.93) nor the development of obesity between baseline and the second evaluation (OR=0.80, 95% CI: 0.48-1.33, P=0.39) were significantly associated with vitamin D status. In subjects who were non-obese (BMI <30 kg/m²) at the second evaluation, 25-hydroxyvitamin D values ≤ 17 ng/ml (≤ 42.5 nmol/l) were significantly associated with an increased risk of developing obesity in the next 4 years (OR=2.35, 95% CI: 1.03-5.4, P=0.040 after diverse adjustments). We conclude that vitamin D deficiency is associated with an increased risk of developing obesity.

We undertook a population-based cohort study in Pizarra (Spain). Anthropometric and nutritional variables were recorded for 613 persons. The type of fat used was determined by measurement of the fatty acids contained in cooking oil. Serum fatty acid was used as a biological marker of the type of fat consumed. Obesity incidence in persons who were not obese at baseline was greater in those who consumed sunflower oil (Group 1: 41.5 (95% CI, 25.4-67.8) cases per 1000 person-years) than in those who consumed olive oil or a mixture of oils (Group 2: 17.3 (95% CI, 11.6-25.8) cases per 1000 person-years). The risk of developing obesity over 6 years, adjusted for age, sex, physical activity, smoking, instruction level, energy intake and baseline BMI, was 2.3 (95% CI, 1.06-5.02) in group 1 compared with that in group 2. The increase in the prevalence of obesity in the free-living population is associated with the type of fatty acids in the diet.

The aim of this study was to test the hypothesis of an association between the -30G>A polymorphism of the promoter of the glucokinase gene and the prevalence and incidence of obesity. We studied the -30G>A polymorphism of the glucokinase gene promoter in 981 persons, of whom 866 were seen again 6 years later. All the persons underwent an oral glucose-tolerance test and the BMI (weight/height(2)) was recorded. The -30G>A polymorphism of the glucokinase gene promoter was studied using RFLP-PCR. At the initial study, the probability of having a BMI > or =25 in carriers of the A allele was significantly lower than expected by chance (odds ratio (OR) = 0.63; 95% confidence interval (CI) = 0.456-0.885). In those persons with a BMI > or =30 at the first study, the probability at 6 years of losing weight (reaching a BMI < 30) was greater in carriers of the A allele (OR = 0.22; 95% CI = 0.087-0.576). The increase in weight over these 6 years, taken as a continuous variable, was significantly less only in those persons who were originally obese (P = 0.018). In conclusion, in a population from southern Spain, carriers of the A allele of the -30G>A polymorphism in the promoter of the glucokinase gene had a lower risk for obesity and the likelihood of losing weight was greater in those obese persons who had the A allele (GA or AA).

Recent studies have confirmed important regional differences in the prevalence of obesity, as well as a tendency for this prevalence to increase. Determination of the social factors involved in obesity may be very useful to design intervention and prevention strategies. This transverse study was undertaken in Pizarra (Malaga, Spain) from a random sample of the population between 18 and 65 years of age (n = 1226). All participants were interviewed and given a physical examination. Standardized anthropometrical measurements were made, and a baseline blood sample was taken after an oral glucose tolerance test. The overall prevalence of obesity (BMI > 30 kg/m2) was 28.8%. This figure increased continuously from 10% in the group aged 18-25 years to above 50% in the groups aged over 55 years. This prevalence is higher than that reported in most other studies in Spain. The obese persons ate differently, at least from a qualitative viewpoint, probably more saturated fats and fewer unsaturated fats, and had a different behaviour concerning alcohol and smoking. Marital status was related with the rate of obesity, and the close relation between the level of education and the risk of obesity was confirmed (OR = 3.8 for being obese and having no education compared to having university studies). The most important consequence of the study was that all these factors are potentially modifiable and preventable. An increased level of general education in the population may well contribute decisively to a reduction in the prevalence of obesity.