The literature concerning NES typology remains meager. In 2010, Allison and colleagues (2010) highlighted the need for a more detailed examination of three possible NES subtypes based on evening hyperphagia and/or nocturnal ingestions. The current study informs the question concerning NES subtypes and differences in eating pathology. To the authors’ knowledge, only one study has examined differences among potential NES subtypes regarding sleep patterns , but no studies have examined disordered eating symptom differences. Using data from an online-based community (MTurk) sample, three NES groups were created: an EHNI group, which consisted of individuals who met criteria for evening hyperphagia and reported nocturnal ingestions; an EHO group consisting of individuals who met criteria for evening hyperphagia but indicated that they never consumed snacks during sleep awakenings; and a NIO group, consisting of individuals who reported nocturnal ingestions, but did not meet criteria for evening hyperphagia.
The hypothesized differences among NES subgroups were partially supported by the results. Overall, the EHNI group reported more binge eating symptoms and food addiction symptoms than the EHO and NIO groups. The EHO and NIO groups did not differ from each other in terms of binge eating or food addiction symptoms. These results suggest that a NES subtype in which both core criteria are met (i.e. EHNI) might indicate more binge eating and food addiction symptoms than in the case in which only one of the two NES core criteria exist (i.e. EHO or NIO). The hypothesis regarding differences in binge eating symptoms between the EHO and NIO groups was not supported, which was unexpected given that evening hyperphagia seems to be more specific to binge eating pathology [23, 37] and nocturnal ingestions are not characterized by bingeing behavior . Thus, binge eating symptoms were expected to be more prevalent among the EHO group in comparison to the NIO group, but the results from this study did not support this notion.
Food addiction symptoms and NES symptoms were significantly correlated in the current study as in previous studies [29, 38]. Moreover, individuals who were in the EHNI group reported more food addiction symptoms on average than those in the EHO and NIO groups. This suggests that individuals who report both evening hyperphagia and nocturnal ingestions are more likely to report more food addiction symptoms than individuals who only report one of the two NES core criteria. Exploratory analyses also revealed that more participants (61.3%) in the EHNI group with probable food addiction diagnosis (i.e. clinical distress and at least 3 other food addiction symptoms)  displayed more food addiction symptoms than did participants with probable food addiction in the EHO and NIO groups. The EHO and NIO groups did not differ in terms of food addiction symptoms. Accordingly, reporting NES symptoms that would fit within an EHNI subtype may raise a concern for probable and more severe food addiction diagnosis in an individual than reporting EHO or NIO alone.
There are a few possible explanations as to why the EHO and NIO groups did not show significant differences regarding binge eating or food addiction symptoms. For example, it is possible that the self-reported measures did not capture the most accurate representation of some of these symptoms; conducting a clinical interview in the future could clarify these results. Regarding food addiction symptoms, even though both EHO and NIO groups had a similar frequency of food addiction symptoms, it is possible that the specific symptoms that each group reported may have been different. This, however, was beyond the scope of the purpose of the current study. Additionally, one must bear in mind that other cognitive and behavioral differences not included in the current study may exist between an evening hyperphagia-only subtype and a nocturnal ingestions-only subtype. For example, compared to patients that report evening hyperphagia with/without nocturnal ingestions, patients who only meet the nocturnal ingestions criterion seem to have longer nocturnal eating episodes and it takes them longer to fall back asleep . NES is also characterized by evening mood deterioration, e.g. , and some data suggest that NES patients who experience nocturnal ingestions report more severe depression symptoms than those without nocturnal eating episodes . Unfortunately, researchers have only compared NES patients with nocturnal ingestions to those without, thus failing to differentiate between subtypes concerning evening hyperphagia with and without nocturnal ingestions. Additional research examining possible differences among all three latent NES subtypes is warranted.
Research on disordered eating behaviors related to obesity is essential to inform preventative strategies and treatment. Multiple factors appear to influence the link between NES and BMI, such that some studies have found a direct association while others, including the current study, have not (see  for review). Still, symptoms of NES can be expected to (at least) contribute to excess weight. For example, evening hyperphagia is common among individuals with obesity  and nocturnal eating is associated with significant weight gain . In addition to other, more severe eating pathology that might be present , NES patients are undoubtedly at high risk for developing and maintaining obesogenic behaviors and metabolic syndrome . The multifactorial nature of NES demands several preventative and treatment options. Specifically, lifestyle modification that includes a balanced, nutrient-dense diet, increased physical activity, and modifying the individual’s environment are some of the most well-known obesity preventative strategies . It is also important to note that obesity and NES preventative strategies may start as early as in childhood and adolescence [44–45]. NES treatment has received more attention in clinical research than preventative strategies have, however, obesity prevention may serve as a safeguard for development or worsening of NES and comorbid eating pathology (notably BED and food addiction symptoms). More research is needed in this area, especially for an EHNI subtype which may require more intensive treatment than the single NES criterion subtypes.
Among U.S. adults, obesity has continually increased in the last decade with obesity rates rising to 42.4% . Obesity is linked to an increased risk of a variety of serious medical conditions along with premature death and reduced health-related quality of life, making effective treatment imperative [47–48]. It is crucial to examine eating behaviors that contribute to significant weight gain in the first place  given the obesity epidemic in the U.S. and many other countries . Behavioral weight loss treatment involves the use of cognitive behavioral therapy [(CBT) e.g., self-monitoring, social support, cognitive restricting] to lower caloric consumption and increase physical activity. This gold standard treatment can result in a weight reduction of up to 10% of body weight . However, there is ample room for improvement because only around 20% of individuals enrolled in this type of treatment program are able to lose this amount of weight and keep it off for at least one year . One possibility to explain the weight loss struggle is disordered eating comorbidity. When both evening hyperphagia and nocturnal ingestions are present, assessing for binge eating and/or food addiction symptoms would be beneficial in clinical research and practice. On the other hand, assessing for binge eating and food addiction symptoms may not be as crucial if only one of the two NES core criteria are present. If it is determined that a client meets the threshold of both evening hyperphagia and nocturnal ingestions, then behavioral weight loss treatment could be supplemented with treatment targeting NES symptoms such as pharmacotherapy (e.g., sertraline, escitalopram) . Non-pharmacological treatments are also an option such as progressive muscle relaxation, bright light therapy, or CBT for NES which has consisted of sleep hygiene, healthy nutrition strategies, and psychoeducation . CBT for NES seems particularly promising given that behavioral weight loss treatment already incorporates the use of CBT.
Finally, it is important to consider the mechanisms that underlie problematic eating behavior. For example, problems with obesity and overeating are often linked to a history of trauma [31, 53–54] and its sequalae, such as PTSD symptoms and poor emotion regulation, e.g. [27, 55]. Another example is emotional eating, or the tendency to overeat in response to negative affect, which appears to play a significant role in the association between night eating and BMI as well as binge eating . Clinical NES diagnosis may be associated with lack of appetite in the morning, insomnia, problematic beliefs about eating to aid sleep, and mood deterioration in the evening; thus, future research should explore other psychopathological differences that may exist between NES subtypes and which mechanisms may influence those relationships.
4.1 Strength and limits
The findings of the current study must be interpreted in the context of certain limitations. The absence of experimental manipulation and the cross-sectional nature of the data do not allow for any conclusions about causation between NES and other eating pathology. Additionally, data collected from participants were self-reported, and future research should examine these constructs using other methodology, such as clinical interviews. Another limitation was that the sample consisted mostly of Caucasian, non-Hispanic participants, which makes it difficult to know whether the results would generalize to individuals with a different racial or ethnic background. Future studies should aim to recruit and compare groups of equal size because it could reveal important group differences. Despite the differences in group sizes in the current study, a strength of the current study is a larger sample than what Loddo et al. (2019) used to compare NES subtypes. There is a need for a better self-report assessment of NES subtypes; however, the current study provides guidance for using specific NEQ items related to evening hyperphagia and nocturnal ingestions to assess NES subtypes. Another strength is that the hypothesis formulation was based on a comprehensive literature review of NES typology and how binge eating and food addiction symptoms relate to NES symptomology. The results provide novel insights regarding NES subtypes and implications on weight-related complications.