ADHD and obesity: Relationship and contributing factors.
ADHD and overeating
In the last number of years, evidence has been increasingly showing the association between ADHD and obesity. Published in 2018, the first genome-wide association study of ADHD (GWAS) demonstrated that obesity-related phenotypes show significant genetic overlap with ADHD.
Significant genetic overlap with ADHD. The results of the GWAS suggested a shared genetic transmission for ADHD and obesity. This significant relationship was also true for forty-two other disorders, including major depression, educational outcomes, smoking, insomnia, and mortality. Therefore, a genetic link may partly explain the wide-ranging comorbidity seen in ADHD (Demontis et al., 2018).
Interestingly, the association was true for non-treated subjects only, as individuals taking stimulants did not have an increased risk of obesity. Stimulant treatment may promote increased behavioural control and less impulsive, calorie-rich snacking. Stimulants also have a common side effect of appetite suppression.
Stimulant treatment may promote increased behavioural control and less impulsive, calorie-rich snacking. Stimulants also have a common side effect of appetite suppression.
The significant association was found to be true for both children and adults and was found even when hyperactivity was associated with the disorder. Hyperactivity is more common in children, and one would expect active children to “burn” more calories. Of note, population studies show that children not receiving treatment have an increased risk of being overweight.
Overeating and underexercising can lead to a positive energy balance, where more calories are accumulated than expended. This can also result from a sedentary lifestyle. The ADHD symptoms of impulsivity and inadequate planning can contribute to poor meal planning, irregular eating patterns (e.g. skipping breakfast), eating binges, unhealthy food preferences and lack of a
structured exercise routine. Indeed, binge eating and bulimic behaviours are more common in ADHD (Hanson et al., 2020). Skipping breakfast is common in ADHD and may increase appetite later in the day, predisposing to overeating or binging. Forgetting to eat may be related to poor concentration and disorganisation and the disrupted circadian rhythm in ADHD. With late bedtimes, the delayed sleep phase is associated with snacking at night, when metabolic processes do not adequately digest glucose, leading to disturbed insulin response. Nocturnal eating and night-time activity are thus risk factors for obesity and diabetes (Qin et al., 2003).
Another possible mechanism may include dysregulation of dopamine, related to both executive dysfunction in ADHD and “food addiction.”
Dopamine levels in the brain increase when food is present, even if the person does not eat it. Dopamine is linked to the reward system, causing improved mood when levels increase. By activating the dopaminergic pathways, eating becomes a pleasurable task.
Thosewithattentiondeficitdisorder, in turn, has lower dopamine levels, particularly in the prefrontal cortex. Thus, any action that increases the dopamine levels, such as eating, will be appealing to those with ADHD.
In addition, associated comorbidities may play a role. One of the commonest comorbid disorders in ADHD is the late sleep phase. This often results in sleep deprivation, also very common in ADHD (Bijlenga et al., 2013; Kooij & Bijlenga, 2013). Shorter sleep also dysregulates the appetite hormones leptin and ghrelin, increasing appetite, especially for carbohydrate-rich foods (Copinschi et al., 2014)
In one study, 60% of adults aged 18-56 with ADHD (n=120) suffered from eating problems, particularly binge-eating or eating binges. Most patients described their eating behaviour as ‘impulsive’ or ‘to calm down. In almost 40% of patients, eating binges occurred once or twice a day. In 40%, at least once a week and in the rest, at least once a month (Kooij, 2001).
Such is the association between ADHD and obesity. According to a critical study by Levy et al., obese individuals seeking medical weight loss or bariatric surgery should be evaluated for ADHD and treated before intervention. ADHD should be considered a primary cause of weight loss failure in the obese. Treatment of ADHD is associated with significant long-term weight loss in individuals with a lengthy history of weight loss failure. Stimulant treatment has positive effects on self-directedness (achieving a weight loss goal), persistence (sticking to an eating plan), and reducing novelty-seeking behaviours (reducing impulsive overeating) (Levy et al., 2009).
In summary, obesity is associated with ADHD and should be excluded in obese individuals presenting for treatment. Optimal management of ADHD does not stop with an accurate diagnosis of the ADHD itself: This is inadequate if the comorbidities are not identified and treated. However, treating ADHD and its comorbidities, including obesity, promotes better bodily and psychological outcomes.
