Sex Differences in the Relationship between Chronotype and Eating Behaviour: A Focus on Binge Eating and Food Addiction

Overeating is a psychological and behavioural factor contributing to overnutrition, one of the key elements in the manifestation of obesity [1,2]. Depending on the level, it could result in addiction, such as food addiction, or compulsive behaviour, such as binge eating [3].

Food addiction is a novel construct that could lead to the development of different phenotypes of obesity and eating disorders. The core concept revolves around the aspect of certain foods (mostly highly palatable and ultra-high processed foods) being able to promote addictive-like substance abuse behaviour in some individuals [4]. This kind of food shows similarities between sugar, any palatable food, and addictive drugs such as cocaine, amphetamines, nicotine, and morphine [5,6]. The greater availability and related exposure to advertising of low nutritional quality and energy-dense foods that look attractive, hyper-palatable, cheap, and ready to eat [7] lead to higher trends of food addiction, especially in overweight and obese subjects. These circumstances confirm a solid correlation between food addiction and a higher BMI [8]. In this context, binge eating indicates overeating in combination with a lack of control. The latter is defined as eating a quantity of food in a discrete period of time that is unquestionably greater than what most people would consume under similar circumstances [9]. When it occurs at least once a week for 3 months without consistent compensatory behaviours to limit weight gain, unlike bulimia nervosa, it is defined as binge eating disorder [3]. BE is also present in anorexia nervosa, bulimia nervosa, and night-eating syndrome [3], and it is particularly prevalent in individuals who underwent weight-loss treatments, showing increased difficulty in weight maintenance compared to controls and, thus, promoting weight-cycling [10].

Predictors were largely similar across overeating categories: both food addiction and binge eating are predicted by similar risk factors that vary in severity [2], such as female sex, young age, being overweight, sedentariness, compulsive alcohol consumption, insomnia, impulsivity, mood, anxiety disorders, craving and emotional eating [11,12], with chronotype emerging as an influencing factor.

Chronotype represents the individual circadian typology that captures the natural inclination of psychological, behavioural, and biological manifestations with an approximately 24 h oscillation, called a circadian rhythm [13]. Chronotype ranges from morningness to eveningness, with morning-types (M-Types) having their activity peak performance in the first part of the day, while evening-types (E-Types) need time to feel rested after awakening and have their peak level of physical and mental efficiency from the late afternoon [14]. Intermediate or neither-types (N-Types) are individuals without a pronounced circadian preference. E-Types are mostly prime-aged and male adults with unhealthy lifestyles, understood as patterns of physical activity, diet, and sleep hygiene [15,16,17]: they have sedentary activity, smoking habits, and poorer sleep patterns, e.g., fewer sleeping hours, irregular sleep schedules and/or sleep apnoea, than M-Types [18,19,20]. Sex differences in chronotyping are also reported, with most studies showing that males tend to be more likely than females to be in the evening/late chronotypes [19]. Concerning eating habits, E-Types are characterized by lower adherence to a healthy diet, such as the Mediterranean diet: they consume more calories in terms of proteins, simple carbohydrates, and saturated fatty acids during the evening. These calories mainly come from confectionery food, fast foods, and sugar-sweetened beverages, resulting in an overall lower intake of minerals and vitamins from fruits, vegetables, fish, pulses, and cereals [19,20,21]. Their eating behaviour is typified by night times, larger food portion sizes, and longer time intervals between meals. Moreover, they show a greater propensity for food cravings, emotional eating, reduction of control over diet, and the problem of controlling the amount of food eaten [20,22], probably caused by a higher prevalence of impulsivity, anxiety, and depression [23]. All these aspects lead to an altered body composition, such as higher body mass index (BMI), waist circumference and body fat, and the consequent higher prevalence of metabolic disorders [24]. Accumulating evidence proposes the disruption of the light–dark cycle, typical of E-Types, as a risk factor for obesity disease, food/eating addiction, and substance dependence, which risks triggering the onset of eating disorders [11,25]. In line with what has just been stated, food addiction is associated with insomnia and impulsivity [11], and binge eaters usually have substandard sleep quality and sleepiness during the day [26]. A recent narrative review highlighted how E-Types are more prone to suffer from an eating disorder such as food addiction or night-eating syndrome in every age group [27], especially if they are males. However, the studies focused on healthy subjects and did not include known factors influencing the risk of developing binge eating or food addiction (adherence to the Mediterranean diet, physical activity, smoking, nutritional status) as potential variables influencing the link between eveningness and the development of eating disorders. Indeed, overweight and obesity are associated or may be the manifestation of altered eating behaviour, with known differences in the pathogenesis between males and females [28,29]

Despite these sex differences in both eating behaviour and chronotype, to the best of our current knowledge, no previous study has investigated whether and how the interaction between sex and chronotype may influence the development of various pathologies as alterations in eating behaviour [19]. In such a scenario, we carried out a cross-sectional study to investigate the sex differences in the relationship between chronotype and either binge-eating disorder or food addiction in Caucasian adults with overweight or obesity, considering lifestyle factors.

Of the 856 participants who came to ICANS-DIS, 106 were excluded: 88 (10%) did not meet the inclusion criteria and 18 (2%) did not complete all questionnaires. A total of 750 participants were included in the analysis with an eligibility rate of 88% (see Figure 1).

The general characteristics of the study subjects are reported in Table 1.

A total of 70% (n = 525) of participants were women and 30% (n = 225) were men. In our population, 32% (n = 240) were M-Types, 9% (n = 68) were E-Types, and the remaining were N-Types. A total of 21% (n = 158) of participants reported food addiction and 13% (n = 98) had a probability of binge eating, while only 6% (n = 45) reported a risk of having both food addiction and binge eating.

No difference in BMI, binge eating, and food addiction prevalence occurred among the chronotypes. However, rMEQ scores were significantly lower in E-Types compared to M-Types (10 ± 1 vs. 19 ± 1, p < 0.001), as expected, and Mediterranean diet adherence was lower in E-Types (6 ± 2 vs. 7 ± 2, p < 0.05).

We investigated the sex differences in the relationship between chronotype and overeating, such as binge-eating behaviour and food addiction, considering lifestyle factors such as physical activity, smoking habits, and adherence to the Mediterranean diet. Overall, we found that being E-Type was an overeating predictor only in men: notably, E-Type males show higher levels of both binge eating and food addiction than M-Type males, and reach levels similar to those of females, which are higher in all categories of chronotype. In fact, we found no correlations between chronotype and pathological overeating in females at any level, confirming only young age, high BMI, and low adherence to Mediterranean diet as predictors of food addiction. In particular, we found that the direct effect of chronotype on binge-eating and food-addiction scores was not significant, as reported in previous studies [15,17,20,21,22,37], but the interaction between sex and chronotype was significant, highlighting how the effect of chronotype on the development of disorders such as eating disorders is mediated by sex differences. This may be due to the fact that our sample consists of middle-aged participants (30–65 years), in whom sex differences in chronotype expression are still relevant [19], but also to the fact that many aspects of lifestyle, such as smoking, exercise, and dietary patterns, were taken into account when examining this relationship. Future studies would need to be evaluated in the older population, where these differences tend to diminish until they disappear altogether.

The association of the later chronotype (eveningness) and higher scores of binge eating and food addiction are consistent with a recent systematic review on a different population [38] which shows that E-Type children and adolescents had higher BMI, consumed more junk food, and suffered from food addiction and night-eating syndrome. This illustrated how lifestyle factors such as low adherence to the Mediterranean diet can partially explain the contribution of chronotype to compulsive overeating. Little but growing evidence is trying to investigate how circadian rhythm disruptions may characterize either symptoms or modulators of overeating, which could be explained by the link between insomnia and night-eating syndrome [39] but also by the loss of the circadian rhythmicity of metabolic and hedonic regulation of feeding due to the social jet-lag and a gradual increase of prevalence of emotional eating [22,26]. These results are also consistent with the findings of Aoun et al. [23]: they found that healthy male M-Types have lower uncontrolled eating and more cognitive restraint related to food when compared to male E-Types, who are more likely to engage in addictive eating patterns [11]

In addition to the high propensity of E-Types to addiction and substance dependence [40], such as high-calorie foods and beverages, caffeine, alcohol, and fast food, especially at night and during weekends [26], it is well known that binge eaters and subjects with food addiction are more prone to sleep and circadian disturbances. Our results show how these aspects are more probable in men and could explain the link between eveningness, food addiction, and male sex. However, how to explain these sex differences still remains to be investigated. Some biological mechanisms could probably act together. Parikh et al. [41] showed how different responses to solar UV exposure induce food-seeking behaviour in men but not in women, with an increase in ghrelin levels and appetite in men during the daytime; this, when combined with the lack of time due to increasing work schedules, results in overeating in the evening hours or during the weekend. Joye et al. [42] explained how sex hormones and genetic sex regulate nearly all circadian parameters because of sex-specific differences in the cells of the suprachiasmatic nucleus influenced by sex hormones and, at the same time, influence circadian behaviour. In addition, disruptive appetitive behaviour, typical of subjects with binge eating and food addiction later in the daytime, could serve as an external signal to the central circadian pacemaker in maintaining and fuelling the vicious cycle between eveningness and overeating [43].

What can be deduced, however, is that chronobiology and its sex differences need to be involved in lifestyle analysis in overeating disorders, so that dietary and behavioural treatment can be tailored according to chronotype and sex. More specifically, nutritional and behavioural therapies might differ from chronotype to chronotype: e.g., during the COVID-19 lockdown, a well-monitored hypocaloric diet based on the Mediterranean diet model improved binge-eating behaviour and contributed to the individuals’ return to their chronotype and physiological eating rhythms [44]. Moreover, in a U.S. intervention in women with gestational diabetes, a chrononutritional and sleep hygiene intervention significantly reduced the proportion of women with suboptimal glycaemic control thanks to the reduction of carbohydrate intake during the evening hours [45]. Additionally, women with the evening chronotype experienced significant weight loss and a reduction in fat mass, as well as an increase in free-fat mass and phase angle compared with women with the morning chronotype, reporting the chronotype score as the main predictor of weight loss during a dietary intervention with the very low-calorie ketogenic diet [46]. Furthermore, E-Types, when compared with M-Types, lost less weight (percentage of excess weight loss) after bariatric surgery (p = 0.015) and, from the fourth year after the bariatric surgery, they reported a higher weight regain (p < 0.05), especially in subjects with C-Carriers of the CLOCK gene, a component of the circadian system that displays a less robust circadian rhythm with sleep reduction and increased values of plasma ghrelin [47].

To sum up, the circadian and genetic assessment could provide tailored weight loss recommendations in subjects who underwent bariatric surgery. In this scenario, chronotype could be considered a valuable tool to recognize a particular set of participants needing more intensive treatments. If M-Types are to find beneficial outcomes from the first line of interventions, being male and E-Type, and, therefore, more susceptible to a greater change in body composition and a higher risk of addiction and eating disorders, it would require a more invasive nutritional and behavioural intervention: the amount of calories deficit and the dietary composition must be considered, as well as the timing and frequency of intake combined with surgery and medication. We are in an era where personalized approaches are promising to reduce the burden of several current problems in nutrition research, and the incorporation of Machine Learning into Precision Nutrition research could help us to better phenotype and treat different subjects with different levels of diseases [48].

To the best of our knowledge, this is the first study among adults with overweight and obesity to examine the interaction of sex differences in the contribution of chronotype to overeating, both regarding binge eating and food addiction. Our study contributes to the growing body of evidence on the interaction between chronotype and eating behaviour, and the role of both sex and lifestyle in the interaction. Notwithstanding these critical strengths and considerations, some potential limitations need to be emphasized. The sample size of men was lacking compared to women; however, the dataset contained ~94 observations per degree of freedom of the model used to describe the relationship between chronotype and either binge-eating disorder or food addiction, and so should be able to adequately express the relationship without the risk of overfitting of bias in the interpretation of the results [49]. Additionally, only the risk of dietary change could be analysed, since the results of the questionnaires were not confirmed by expert diagnosis. Finally, the cross-sectional design makes it impossible to establish a cause-and-effect relationship. Therefore, further research is necessary in order to understand this association and prospective longitudinal studies are needed to identify causality between chronotype and eating disorders.

In conclusion, these results showed that chronotype is associated with binge-eating behaviour and food addiction, but only in men, emphasizing the role of chronobiology and sex differences as determinants of appetite dysregulation in overweight and obesity.