1. Introduction
Mexico presents one of the highest obesity rates in the world [
1]. The national overweight and obesity prevalence in Mexico is 72.5% [
2]. Conventional weight-loss interventions seem to be ineffective in the long term. Initially, people are highly motivated, but multiple factors affect their food behavior during treatment. Such factors include cultural, environmental, genetic, and psychosocial determinants [
3].
In Mexico, acculturation has contributed highly to an altered food behavior. During the Spanish colonization, the native Mesoamerican staple foods were merged into the Old-World cuisine, creating traditional, regional dishes that are considered nourishing. Currently, due to the nutrition transition driven by industrialization, Mexicans have switched from eating a variety of healthy, pre-Hispanic dishes with Spanish influence to highly processed foods [
4]. In addition, Mexicans socialize around food gatherings, and now, the conspicuous consumption of processed foods seems to be deeply rooted in Mexico’s food culture [
5]. Furthermore, emotions, self-efficacy, and reward seem to affect food intake [
6,
7,
8]. Self-efficacy is the confidence of an individual to perform a behavior [
9]. A low self-efficacy level has been associated with lower physical activity and unhealthy food patterns [
9,
10]. In contrast, patients with a high level of self-efficacy have better food control and confidence in reading nutrition facts labels, eat healthy foods, and comply with dietary recommendations [
11,
12,
13,
14,
15]. Food reward refers to the momentary value that is given to food by the individual at the time of consumption, and eating based on reward could potentially influence higher energy intake [
16,
17].
Precision nutrition interventions are innovative approaches that focus on genetically based nutrition recommendations. Our research group has suggested a Genome-based Mexican diet (the GENOMEX diet) with regional foods as a nutrigenetic strategy to diminish obesity in Mexico [
18]. This diet considers the presence of adaptive gene polymorphisms related to brain reward, appetite, and energy balance in the Mexican Mestizo population of Western Mexico [
19,
20]. In addition, this diet is rich in fiber, antioxidants, prebiotics, and probiotic substances naturally provided in regional Mexican foods, such as maize, beans, squash, tomato, cacao, amaranth, avocado, chia seeds, and fermented beverages, among others. These foods that may contribute to a healthy microbiota have been recognized as a second brain signaling to the central nervous system, thus modulating emotions and food behavior [
20]. So far, nutrigenetic dietary interventions have been implemented mainly with the “Mediterranean diet”. However, Mexican people’s genetic diversity, cultural and psychosocial contexts may interfere with eating behavior and compliance with dietary treatment [
21,
22].
Studies have shown the link between negative and positive emotions on food intake in adults and the influence of emotions, self-efficacy, and food behaviors while participating in weight-loss studies [
23,
24,
25]. However, it is unknown if nutrigenetic interventions could help to improve emotional and food rewarding behaviors and self-efficacy. We hypothesized that displaying unhealthy food behavior could be ameliorated by eating a genome-based (GENOMEX) diet that considers regional Mexican foods and food culture. Therefore, the objective of this pilot study was to explore the influence of the GENOMEX diet on emotions, self-efficacy, and rewarding behaviors in unhealthy eating.
4. Discussion
In Mexico, overweight and obesity are leading public health problems. Mexicans with these health conditions constantly struggle to maintain long-term dietary changes. This study explored how emotions, self-efficacy, and rewarding behaviors interfere with following a healthy diet during a nutrigenetic intervention. We found that negative emotional factors, such as anxiety, food consumption for reward, and a low level of self-efficacy, predispose Mexicans to consume foods high in fat and sugar. In addition, these factors triggered binge-eating behaviors. However, during a GENOMEX dietary intervention, improvements in unhealthy eating decisions, and higher self-efficacy were found.
In the GENOMEX diet, we recruited participants with metabolic abnormalities no matter the BMI value since it has been reported that normal-weight patients also consume an inadequate hepatopathogenic dietary pattern [
37,
38]. This diet refers to higher consumption of more industrialized, calorie-dense foods and high amounts of saturated fatty acids, cholesterol, and high-fructose foods as well as lower consumption of polyunsaturated fatty acids (ω-3/ω-6), fiber, and micronutrients with antioxidant properties, which leads to metabolic abnormalities [
37]. However, the small proportion of normal-weight patients included in the study may be due to Mexico’s general excess weight problem. Interestingly, all participants regardless of BMI consumed excessive energy, but people with obesity tended to consume more calories and refined grains than the rest of the participants. Normal-weight patients consumed fewer sugar servings. This finding is similar to what has been reported in previous studies, in which unhealthy food patterns were consumed highly among people with higher BMI [
39]. However, during the study, participants decreased their energy intake, sugar, dairy servings, and refined grains and increased the number of servings of vegetables and legumes.
Likewise, emotional factors could be driving unhealthy dietary patterns among West Mexicans. The PHQ-9 questionnaire revealed that 53.6% of participants had mild to severe depression symptoms at the beginning of the study, which gradually decreased. Therefore, a higher proportion of participants with minimal depressive symptoms was detected at the end of the intervention. Similar studies have also reported lower depression symptoms during diet interventions [
40,
41]. Moreover, we assessed if participants were eating based on rewards. We performed a linear regression analysis to assess the effect of reward on dietary intake and we found that a high RED score correlated with a higher fat intake. Other researchers have found that the RED score correlates with BMI and cravings for energy-dense foods coded as savory and sweet foods [
17,
42]. In the present study, there was a higher average RED score of 1.26 (SD = 0.81) compared to those previously reported, in which the average RED score was 0.40 to 0.77 and ranged from 0 to 1.89 [
17,
42]. However, it is plausible that the small sample size could have limited our results.
Additionally, to explore emotional behaviors that contribute to the unhealthy eating of participants during the GENOMEX dietary intervention, we conducted close-ended questions with open-ended follow-ups. As a result, 57.1% of participants considered making frequently unhealthy decisions about their food. Similar findings by other researchers show that patients with obesity made more impulsive unhealthy food decisions in the presence of food and hunger [
43,
44]. Regarding mood and food behavior, 72.6% of participants affirmed that mood influences their food intake, and 71.7% of participants stated that mood prompted them to eat more. Van Strien and colleagues proposed that higher intake is experienced after feelings of sadness [
33]. However, it is not clear if feelings of happiness or even neutral moods could influence a higher intake of foods [
25].
Interestingly, we were able to identify that 76.9% of participants confirmed to experience binge episodes triggered by anxiety in 40% of the occasions. Associations between anxiety and binge eating have been demonstrated [
6,
7]. Furthermore, research from ecological momentary assessment (EMA) studies, which evaluate variables of interest in the natural environment in real time, indicate that increasing negative emotions trigger binge-eating episodes [
45,
46]. This study found that participants reported consuming sugary foods during these episodes at 42.2%, followed by fried foods at 28.9%, and salty foods at 28.9%. We also found that high consumption of servings of fats, refined grains, red meats, grams of sugar, and high energy intake and a high percentage of carbohydrates fats, saturated fats, and proteins were associated with a high risk of binge episodes. This can be explained by the combination of sugary and fatty foods that may generate positive feedback in the brain reward system, triggering overeating [
47].
A high level of self-efficacy has been associated with higher adherence to dietary treatment and healthy eating habits [
9,
10,
11,
12]. In the present study, we found increases in self-efficacy and that a low self-efficacy level was significantly associated with high-frequency consumption of total fats, saturated fats, and a high risk of low consumption of vegetables and fiber (
Table 7). Similarly, changes in self-efficacy level associated with decreases in dietary fat intake in low-income subjects with excess weight have been reported [
48]. Furthermore, a positive correlation between fruit and vegetable intake and high self-efficacy among African American women was reported [
49]. A meta-analysis that assessed behavior techniques to promote self-efficacy found that dietary interventions focusing on self-monitoring, feedback on performance, revision of behavioral goals, provided rewards, or planned social support increased dietary self-efficacy significantly more than interventions that did not [
50]. Moreover, in a pilot study, families that received a weekly free meal kit during 10 weeks with educational preparation tips found increases in self-efficacy [
51]. Additionally, in a Mediterranean diet study, a positive relationship between dietary adherence and self-efficacy were found [
52]. Therefore, we considered clinically important the increments in high self-efficacy level found in the present study because it could help patients to adhere to dietary guidelines and to meet their needs.
In the GENOMEX study, we were focused on the metabolic changes related to the nutrient-gene interactions of the prescribed foods. We did not provide psychological or adherence reinforcement techniques to promote self-efficacy, like the ones used in the social cognitive theory or the transtheoretical model. These strategies have been previously reported with positive results [
50,
53]. Such strategies include motivation, reinforcements, and working on participants’ skills and are based on the social cognitive theory, which focuses on the influence of individual experiences, the actions of others, and environmental factors on individual health behaviors [
54]. In this exploratory pilot study, we did not test the social cognitive theory by describing the participant´s experiences, expectations, or if they developed skills during the intervention that could influence the present results. In addition, we did not evaluate the stages of change of the participants, which is proposed by the transtheoretical model. The transtheoretical model is a guideline to promote positive health behavior changes; it aims to understand individual’s behavioral changes and to describe the process of those changes. The constructs in this model are stages of change (precontemplation, contemplation, preparation, action, maintenance, and termination), self-efficacy, decisional balance, and processes of change. [
55]. It is suggested that as subjects advance through those stages, it is more likely that they perceive more benefits than disadvantages from adopting positive behavior changes when compared to the initial stages.
Nonetheless, during the GENOMEX intervention, we were able to find that symptoms of depression decreased along with unhealthy food decisions. It is plausible that the characteristics of the diet plus the different menus and grocery lists used in the study might have contributed to these positive results. We prescribed foods according to the participants’ genetic and cultural background (beans, corn tortilla, amaranth, chia and pumpkin seeds, tomato, nopal, quelites (regional leafy greens), and avocado) [
18]. A plausible explanation of the changes in mood and self-efficacy could be because this diet also considers the genetic polymorphisms involved to appetite control and energy balance among the Mexican population. Likewise, the prescribed regional foods were rich in fiber and antioxidants with prebiotic and probiotic activity. These foods have been well described to ameliorate gut microbiota performance in terms of mood and cognition by maintaining a bidirectional communication with the central nervous system [
20]. Therefore, it could be possible that the consumption of these prebiotics/probiotics ameliorated unhealthy food behavior and negative emotions by restoring the gut-brain axis. However, these results cannot be generalized because nutrition precision strategies need to be individualized in the context of cultural and regional background of a specific population.
Finally, some limitations in this study were a small sample size since we only considered data from participants who completed the questionnaires during the GENOMEX intervention. Likewise, we were not able to recruit a control group to compare these results with healthy subjects. Additionally, we recognize that the unfeasibility of using a validated questionnaire related to emotions, self-efficacy, and food behavior at each of the subjects’ appointment could limit the present results. However, the strengths of this study were that we selected the main topics that we were interested in to explore the frequency of unhealthy food decisions, perceived self-efficacy, and which emotions triggered patients to eat more and if patients had binge episodes. Furthermore, we used the Patient Health Questionnaire and Reward-Based scale to question the participants about their emotions and self-efficacy level during the study. Additionally, we detected symptoms of depression, low level of self-efficacy, and high rewarding inputs that elicit unhealthy food behaviors. Psychologists usually do not refer these patients to dietitians or recommend making changes in their diet; however, this study provided them with the opportunity to restore their emotions by consuming a genome-based diet. The results presented here will allow us to design further nutrigenetic studies focused on the relationship between polymorphisms of food intake, satiety, and reward genes and food behavior traits.