Clinical and Genetic Associations of Night Eating Syndrome (NES)

Night Eating Syndrome (NES) is a distinct eating disorder marked by a recurring pattern of delayed food intake, characterized by evening hyperphagia (consuming a large proportion of daily calories after dinner) and/or nocturnal awakenings with food consumption. Though less commonly discussed than anorexia nervosa or binge eating disorder, NES can significantly impact metabolic health, sleep, and psychological well-being.

Emerging research is shedding light on both the clinical characteristics and genetic underpinnings of NES, offering new insight into this often misunderstood condition.

Defining Night Eating Syndrome (NES)

According to the International Classification of Sleep Disorders (ICSD-3) and proposed DSM-5 research criteria, a diagnosis of NES includes:

• Recurrent episodes of night eating, manifested as eating after awakening from sleep or excessive food consumption after the evening meal.

• Awareness and recall of the eating episodes (distinguishing NES from sleep-related eating disorder).

• The behavior causes significant distress or impairment.

• The pattern persists for at least 3 months.

• Not better explained by another disorder or substance use.

Night eating is considered problematic when more than 25–50% of daily calories are consumed after dinner or when sleep is consistently interrupted by eating episodes.

Clinical Features of NES

1. Circadian Rhythm Disruption

NES is thought to involve misalignment between circadian rhythms of eating and sleeping, including:

• Delayed peak in appetite-regulating hormones (e.g., leptin and ghrelin).

• Evening delay in melatonin secretion and core body temperature rhythms.

• Increased cortisol secretion at night, suggesting stress-related dysregulation.

These disturbances can contribute to:

• Insomnia and sleep fragmentation

• Mood instability

• Poor appetite in the morning, reinforcing the cycle

2. Psychiatric Comorbidity

NES is frequently associated with:

• Depression and anxiety disorders

• Binge eating disorder (BED)

• Substance use and impulse control disorders

Up to 55% of NES patients report a history of major depressive disorder, and anxiety symptoms often worsen in the evening, contributing to nighttime eating.

3. Obesity and Metabolic Risk

While not all individuals with NES have elevated weight, NES is more common in those with overweight or obesity and may:

• Contribute to insulin resistance

• Disrupt glucose metabolism

• Increase risk for type 2 diabetes and metabolic syndrome

However, weight alone is not diagnostic, and NES can affect people across the weight spectrum.

Differentiating NES from Related Conditions

Condition: Key Features and Distinguishing Factor

NES: Conscious eating at night, delayed eating rhythm Full awareness, eating relieves distress

Sleep-Related Eating Disorder (SRED): Involuntary eating during sleep Amnesia for eating episodes

Binge Eating Disorder (BED): Loss of control during large food intake Binge episodes not limited to nighttime

Bulimia Nervosa: Binging with compensatory behavior Often involves purging, weight concern

Genetic and Biological Associations

1. Family and Twin Studies

Research suggests NES may have a heritable component, although studies are limited:

• Family history of mood disorders, obesity, or eating disorders may be more common in individuals with NES.

• Twin studies indicate that traits related to meal timing, food cravings, and eveningness may have a moderate genetic basis.

2. Gene Variants and Chronotype

Preliminary evidence suggests associations with:

• PER1 and CLOCK genes, which regulate circadian rhythm and meal timing.

• Genetic predisposition to evening chronotype (being a “night owl”) may increase risk for NES-like behaviors.

• Some overlap with genetic markers of obesity and depression, although the specific mechanisms are still under investigation.

3. Hypothalamic and Neuroendocrine Involvement

NES likely involves hypothalamic dysregulation of:

• Leptin and ghrelin, which control hunger and satiety

• Melatonin, which signals sleep onset

• Cortisol, a stress hormone that remains elevated in NES at night

Disruptions in this neuroendocrine axis may make individuals more susceptible to stress- or sleep-triggered eating.

Assessment and Diagnosis

Validated tools for screening NES include:

• Night Eating Questionnaire (NEQ) – Assesses frequency, awareness, and distress related to night eating

• Sleep and eating diaries – Track timing of meals and awakenings

• Actigraphy or polysomnography – May be used if SRED or other sleep disorders are suspected

A comprehensive evaluation should also include:

• Mood and anxiety assessment

• Sleep history

• Weight and metabolic screening

Treatment Options

1. Cognitive Behavioral Therapy for NES (CBT-NES)

Targets:

• Evening cravings and meal timing

• Mood regulation and stress management

• Cognitive distortions related to eating and sleep

Studies show CBT can reduce nighttime eating episodes and improve mood (Allison et al., 2010).

2. Light Therapy

Morning exposure to bright light may help shift circadian rhythms earlier, especially in individuals with delayed sleep phase or evening chronotype.

3. Medications

Some pharmacological options include:

• SSRIs (e.g., sertraline): Shown to reduce NES symptoms and improve sleep

• Melatonin: May help reset circadian misalignment

• Topiramate or other agents: Occasionally used off-label for co-occurring binge eating

Always consult a psychiatrist or physician with experience in sleep and eating disorders before starting medication.

4. Nutritional Support

• Scheduled meals and snacks throughout the day

• Evening routine adjustments to increase satiety before bed

• Support from a registered dietitian specializing in disordered eating

Final Thoughts

Night Eating Syndrome is more than just a bad habit—it’s a biologically and psychologically driven condition that deserves recognition and appropriate treatment. With the right support, including behavioral therapy, sleep regulation, and (when indicated) medication, individuals with NES can experience significant relief and improved quality of life.

Understanding NES through the lens of both circadian biology and mental health allows for a more compassionate, holistic approach to care.

References

• Allison, K. C., Lundgren, J. D., O'Reardon, J. P., et al. (2010). Proposed diagnostic criteria for night eating syndrome. International Journal of Eating Disorders, 43(3), 241–247.

• McCune, A. M., Lundgren, J. D., & Allison, K. C. (2012). Night eating syndrome: A review of the literature. Clinical Psychology Review, 32(1), 49–59.

• Hood, M. M., Reutrakul, S., & Crowley, S. J. (2021). Night eating: Prevalence, predictors, and health outcomes. Current Opinion in Clinical Nutrition & Metabolic Care, 24(4), 287–292.

• Birketvedt, G. S., Florholmen, J., Sundsfjord, J., et al. (1999). Behavioral and neuroendocrine characteristics of the night eating syndrome. JAMA, 282(7), 657–663.

• Goel, N., Stunkard, A. J., Rogers, N. L., et al. (2009). Circadian rhythms, sleep, and metabolism: Influence on energy balance and body weight. Sleep Medicine Clinics, 4(4), 453–471.