Although some previous studies have investigated the association between food insecurity and prevalence of chronic diseases among adults (5, 6), to the best of our knowledge, this is the first study evaluated the association between food insecurity, risk factors related to food insecurity, and NAFLD prevalence in Iran.
More recently, Golovaty et al. (24) investigated the association of food insecurity with NAFLD among 2627 adults in the United States. They found that the estimated prevalence of NAFLD did not differ significantly by food security status (food secure 31% compared with food insecure 34%, P = 0.21). In the same study, in the multivariable model, food-insecure adults were more likely to have NAFLD compared with food-secure adults (24). In the present study, food insecurity prevalence was 56.8% in patients with NAFLD and 26.1% in controls, and this difference was statistically significant. Unhealthy eating habits in patients with NAFLD may contribute to this difference. It is well established that NAFLD is closely associated with overweight and obesity (12, 14). Most of previous studies have reported a significant positive association between inappropriate dietary patterns and NAFLD (12, 25). Nutritional problems in patients with NAFLD include excess consumption of energy, carbohydrates, and lipids, and vitamin and mineral deficiencies (13, 25). In fact, consumption of high-energy-dense foods increases in patients with NAFLD. These foods with a higher energy density including saturated and trans fatty acids, refined grains, and foods with added sugars, tend to have poor nutritional quality (25). On the other hand, previous investigations have also reported a positive association between food insecurity and obesity (5, 22). Food insecure adults may depend on high-energy foods, which can result in overconsumption of energy and result in obesity and obesity-related complications such as NAFLD (3, 6). Accordingly, these inappropriate eating habits in NAFLD patients may contribute to incidence of high food insecurity in these patients.
Patients with NAFLD experience symptoms such as fatigue, anxiety along with depression (26). These symptoms significantly affect patients’ well-being and health-related quality of life. In this study, NAFLD chance in depressed participants was 2.3 (95% CI: 1.34–3.51) times more in comparison with non-depressed ones. Also, numerous population-based studies have reported high prevalence of depression in patients with NAFLD, which is in agreement with this study. Le Strat et al. (26) reported occurrence of 12-month major depression in participants with a liver disease (17.2%), which was significantly higher compared to participants without liver disease (7.0%; Adjusted OR:2.2; CI: 1.2–4.1), after adjusting for a number of socio-demographical, medical and behavioral factors. In addition, a case-control study by Elwing et al. (27) suggested that subjects with NASH showed a significant increase in their lifetime rate of major depressive disorder (MDD) in comparison with control subjects without liver disease matched for age, gender, BMI, and WHR. Interestingly, after adjusting for other clinical confounders, the diagnosis of MDD tended to be associated with steatosis grade (27). Youssef et al. (28) studied the relationship between depression and severity of histological features in 567 patients with NAFLD. Subclinical and clinical depression was reported in 53% and 14% of patients with NAFLD, respectively (28). Importantly, after adjusting for confounders, depression was significantly correlated with more severe hepatocyte ballooning and patients with subclinical depression had a higher possibility of having more severe portal fibrosis (28). Depressive mood influences self-care practices inversely, and thereby elevating risk of long-term complications (29). Some previous studies have indicated the association between dietary patterns and depression (30). In a case control study on a sample of Iranian subjects, it was found that a healthy dietary pattern characterized by a high intake of various vegetables and nuts was associated with a low prevalence of depression after adjusting for non-depression drug use, job, marital status, the number of children, and BMI (30). Additionally, a recent study conducted in Korean adults demonstrated that a healthy dietary pattern rich in vegetables, soybeans, mushroom, white fish, shellfish, and fruits was associated with low depression risk. Whereas an unhealthy dietary pattern rich in white rice, meats, noodles, bread, and coffee increased the risk of depression after controlling for various social, health, and dietary confounders (31). Moreover, observational studies have found an inverse association between adherence to a Mediterranean diet and depression risk (32). Therefore, high prevalence of depression in patients with NAFLD may also be a result of poor nutritional patterns in these patients.
Results of the present study indicated that the prevalence of overweight and obesity was statistically higher in cases in comparison with the controls. Furthermore, patients with NAFLD had significantly higher WC, WHR, WHtR, and BFP compared to those in the control group. Numerous studies reported the association between BMI and NAFLD, which is in agreement with the present study (25). BMI was confirmed as the most useful predictive factor for NAFLD onset in both sexes, in a community-based longitudinal cohort study on 6403 Japanese subjects (33). Additionally, cumulative onset rate of NAFLD was significantly higher in the group with high BMI in comparison with the group with low BMI in both sexes (33). Compared to normal BMI, NAFLD risk was found to have an approximately 4.1 to 14-fold increase in the group with higher BMI (34). Moreover, Fan et al. (15) demonstrated that higher BMI (overweight/obesity) was an independent, dose-dependent risk factor for fatty liver.
NAFLD prevalence is associated not only with higher BMI, but also is strongly related to central fat deposition (35). WC, WHR and WHtR have been considered as alternative indices for abdominal (visceral) obesity in previous studies (35, 36). Abdominal obesity is closely associated with development of metabolic diseases and adverse health outcomes. Measures of body fat distribution, such as WC, WHR, and WHtR have been indicated to be better predictors of morbidity and all-cause mortality compared to overall adiposity (35, 37). Visceral fat compared to subcutaneous fat was considered as better predictor of hepatic steatosis and was associated with NAFLD histological severity (13, 35). In line with our findings, results of a study conducted on 250 patients with NAFLD and 240 non-NAFLD individuals demonstrated that BMI, WHR, and WHtR were significantly higher in patients with NAFLD (38). Moreover, BMI and WHR were identified as the most important NAFLD prognostic factors (38). Findings of our study were also in agreement with another study on 164 cases with NAFLD and 164 controls without NAFLD, which indicated that patients with NAFLD were significantly more likely to be overweight, have abdominal obesity, and a significantly higher body fat content (39). In a recent cohort study conducted on 960 people in north of Iran, a significant positive relationship was reported between anthropometric indices (BMI, WC, WHR, and WHtR) and NAFLD (35). Fung et al. (40) demonstrated that relative risk of NAFLD in subjects with high WC was 2.99. In addition, degree of steatosis significantly elevated with the increase in the WC (40). As mentioned above, an association between overweight, obesity, food insecurity has been reported in previous studies (7, 22). Therefore, both general and abdominal obesity may also indirectly increase the risk of NAFLD. Although some cross-sectional studies failed to identify a direct relationship between obesity and food insecurity in adults (41, 42), most previous studies carried out in Iran and other countries have reported a significant positive association between obesity and food insecurity (5, 22). Prior studies have identified several potential mechanisms including physiological, behavioral, and psycho-social-cultural factors related to this association (43). Generally, behavioral mechanisms resulting in poor dietary quality and physical inactivity are most important factors contributing to the increase in the prevalence of obesity (22, 43). Intake of low-cost and less-varied diets along with high-calorie and nutrient-poor foods coupled with lower intake of fruits and vegetables and lack of physical activity may cause excess weight and obesity. Nutrient deprivation and fluctuations in eating behavior may lead to physiological shifts towards greater energy efficiency, elevated storage of body fat, obesity, and subsequently development of NAFLD (5, 43). In addition, depression related to food insecurity and its subsequent effect on eating behavior is another possible factor influencing relationship between food insecurity, obesity and associated metabolic disorders like NAFLD.
Our findings indicated that patients with NAFLD had lower physical activity levels in comparison with the controls. In agreement with our result, previous studies have demonstrated that individuals with less physical activity are more likely to be affected with NAFLD (44). Increased physical activity decreases hepatic fat content and improves insulin resistance. Improved insulin resistance decreases excess delivery of free fatty acids and glucose for free fatty acid synthesis to the liver. Besides, exercise enhances fatty acid oxidation, reduces fatty acid synthesis, and prevents mitochondrial and hepatocellular damage, in the liver (44).
In the present study, patients with NAFLD had lower SES. In addition, family size, number of children, and children with the ages less than 18 years old were significantly higher in patients with NAFLD in comparison with the controls. In agreement with our findings, many previous studies have found a significant positive relationship between household size, number of children, having children with the ages under 18 years old, lower SES and food insecurity (5, 22, 45). These socio-demographic factors may influence household food security, resulting in changes in dietary patterns and risk of NAFLD. Several studies have demonstrated that NAFLD is more prevalent among men and elderly people (46). Gender distribution was similar between two groups of the present study. Moreover, there was no significant difference in age of the study participants.
In the present work, NAFLD associated with some indicators of dyslipidemia including high TG and low HDL-C levels. In agreement with the present study, a growing body of evidence has shown a close relationship between NAFLD and dyslipidemia (47–49). In a cross-sectional study, high serum levels of TG, TC, LDL-C and VLDL-C and low serum levels of HDL-C were observed in patients with NAFLD (48). In the same study, a significant relationship between TC, HDL-C, LDL-C and VLDL-C and increasing grades of NAFLD was also reported (48). In line with our findings, Tomizawa et al (47) reported that serum concentrations of TG was significantly higher and serum levels of HDL-C was significantly lower in patients with NAFLD compared to those without NAFLD. Importantly, among markers of hyperlipidemia, TG was the strongest predictor of NAFLD (χ2 = 9.89, P = 0.0017). More recently, a cross-sectional study showed that TG/HDL-C ratio was associated with NAFLD in an apparently healthy population, after adjustment for confounding factors (50).A population-based cohort study also demonstrated that higher TG/HDL-C was an independent predictor of incident fatty liver (50). Similarly, in a cross-sectional study involving a large sample of children and adolescents, the odds ratios for NAFLD increased significantly with the increasing tertile of TG/HDL-C ratio, after adjusting for confounding factors (51). Consistently, a close association between TG/HDL-C and NAFLD was found in our present study.
Strengths of the present study were assessing food insecurity as a risk factor for NAFLD, as well as a case-control design in which the controls were selected from the same population with similar characteristics. This study had also some limitations. Sample size was relatively small and the study population did not reflect general population, therefore our results may not be generalized to other populations.