Worldwide type 2 diabetes (T2D) prevalence is increasing dramatically. The present study aimed to evaluate the association between dietary habits and T2D in an Iranian adult population using a cross-sectional analysis of the Shahedieh cohort study. Participants were adults aged 35–70 years (n 9261) from Zarch and Shahedieh, Yazd, Iran, who attended the baseline phase of the Shahedieh cohort study. Dietary habits including meal frequency, fried-food consumption, adding salt to prepared meals and grilled-food consumption were assessed by a standard questionnaire. T2D was defined as fasting plasma glucose (FPG) ≥126 mg/dl according to the American Diabetes Association. Multiple logistic regression assessed the association between dietary habits and T2D. Individuals who consumed a meal more than six times per day compared to three times per day had greater odds for T2D (OR 2⋅503, 95 % CI 1⋅651, 3⋅793). These associations remained significant in a fully adjusted model. There was a significant association between greater intakes of fried foods and prevalence of T2D (OR 1⋅294, 95 % CI 1⋅004, 1⋅668) in the adjusted model. No significant associations were observed between other dietary habits (adding salt to prepared meals and grilled-food consumption) and odds of T2D in all crude and adjusted models. In conclusion, we have highlighted the association between meal and fried-food consumption frequencies with risk of T2D. Large longitudinal studies in different ethnicities are needed to confirm these associations.

The interplay between the fat mass- and obesity-associated (FTO) gene variants and diet has been implicated in the development of obesity. The aim of the present analysis was to investigate associations between FTO genotype, dietary intakes and anthropometrics among European adults. Participants in the Food4Me randomised controlled trial were genotyped for FTO genotype (rs9939609) and their dietary intakes, and diet quality scores (Healthy Eating Index and PREDIMED-based Mediterranean diet score) were estimated from FFQ. Relationships between FTO genotype, diet and anthropometrics (weight, waist circumference (WC) and BMI) were evaluated at baseline. European adults with the FTO risk genotype had greater WC (AAv. TT: +1·4 cm; P=0·003) and BMI (+0·9 kg/m2; P=0·001) than individuals with no risk alleles. Subjects with the lowest fried food consumption and two copies of the FTO risk variant had on average 1·4 kg/m2 greater BMI (Ptrend=0·028) and 3·1 cm greater WC (Ptrend=0·045) compared with individuals with no copies of the risk allele and with the lowest fried food consumption. However, there was no evidence of interactions between FTO genotype and dietary intakes on BMI and WC, and thus further research is required to confirm or refute these findings.

Overweight/obesity, CVD and type 2 diabetes are strongly associated with nutritional habits. High consumption of fried foods might increase the risk of these disorders. However, it is not clear whether the use of vegetables oils for cooking increases the risk of chronic diseases. We systematically searched for published studies that assessed the association between vegetable oil consumption including fried food consumption and the risk of overweight/obesity or weight gain, T2DM or the metabolic syndrome, and CVD or hypertension in the following databases: PubMed; Web of Science; Google Scholar. Keywords such as ‘fried food’ or ‘vegetable oil’ or ‘frying’ or ‘frying oils’ or ‘dietary fats’ and ‘weight gain’ or ‘overweight’ or ‘obesity’ or ‘CHD’ or ‘CVD’ or ‘type 2 diabetes’ or ‘metabolic syndrome’ were used in the primary search. Additional published reports were obtained through other sources. A total of twenty-three publications were included based on specific selection criteria. Based on the results of the studies included in the present systematic review, we conclude that (1) the myth that frying foods is generally associated with a higher risk of CVD is not supported by the available evidence; (2) virgin olive oil significantly reduces the risk of CVD clinical events, based on the results of a large randomised trial that included as part of the intervention the recommendation to use high amounts of virgin olive oil, also for frying foods; and (3) high consumption of fried foods is probably related to a higher risk of weight gain, though the type of oil may perhaps modify this association.

Reported associations between the consumption of fried foods and the incidence of obesity or weight gain make it likely that fried food consumption might also be associated with the development of hypertension. However, evidence from long-term prospective studies is scarce. Therefore, the aim of the present study was to longitudinally evaluate this association in a prospective cohort. The SUN (Seguimiento Universidad de Navarra) project is a Mediterranean cohort study of university graduates conducted in Spain, which started in December 1999 and is still ongoing. In the present study, we included 13 679 participants (5059 men and 8620 women), free of hypertension at baseline with a mean age of 36·5 (sd 10·8) years. Total fried food consumption was estimated at baseline. The outcome was the incidence of a medical diagnosis of self-reported hypertension during the follow-up period. To assess the association between the consumption of fried foods and the subsequent risk of developing incident hypertension during the follow-up period, Cox regression models were used. During a median follow-up period of 6·3 years, 1232 incident cases of hypertension were identified. After adjusting for potential confounders, the adjusted hazard ratios for developing hypertension were 1·18 (95 % CI 1·03, 1·36) and 1·21 (95 % CI 1·04, 1·41) for those consuming fried foods 2–4 and >4 times/week, respectively, compared with those consuming fried foods < 2 times/week (P for trend = 0·009). In conclusion, frequent consumption of fried foods at baseline was found to be associated with a higher risk of hypertension during the follow-up period in a Mediterranean cohort of university graduates.