ADHD, obesity and eating disorders

Author: Ulrich Brennecke
Review 10/2024: Dipl.-Psych. Waldemar Zdero

Eating disorders and obesity are common with ADHD.¹²

Children with ADHD and also children with subclinical ADHD (ADHD that is too mild for a diagnosis) have an increased body fat percentage.³ According to a meta-analysis (k = 14 studies with n = 24,455 adults and k = 3 studies with n = 299 adolescents), the prevalence of ADHD in candidates for stomach reduction is threefold higher in adults (8.94 % to 9.90 %) and sixfold higher in adolescents (28.73 %).⁴

• 1. ADHD and overweight/obesity/obesity
  • 1.1. ADHD twice as common with obesity (children + 20%, adults + 55%)
  • 1.2. ADHD treatment works against obesity
  • 1.3. Stomach reduction less effective for ADHD symptoms?
  • 1.4. Obesity and addictive behavior
• 2. ADHD and eating disorders
  • 2.1. Binge eating twice as often
  • 2.2. Bulimia 6 to 8 times more common in women with ADHD
  • 2.3. Anorexia is 2.2 times more common with ADHD
  • 2.4. Compulsive grazing (snacking) increases the risk of ADHD by 8 times
• 3. ADHD and diabetes
• 4. Cortisol, metabolism and body fat
• 5. Links between ADHD and eating disorders
  • 5.1. Emotional dysregulation and impulsivity
  • 5.2. Dopamine

1. ADHD and overweight/obesity/obesity¶

1.1. ADHD twice as common with obesity (children + 20%, adults + 55%)¶

The prevalence of ADHD is higher in people who are extremely overweight than in the general population. In an extremely long duration study over 33 years, it was found that 41.4% of all men who suffered from ADHD-C as children developed massive obesity as adults, while only 21.6% of those without a childhood ADHD diagnosis were affected. The frequency of obesity among people with ADHD doubled (albeit with extremely different starting levels) in the USA from 21.6 % without ADHD to 41.4 % with ADHD⁵ and in Germany from 10.2 % without ADHD to 22.1 % with ADHD.⁶
An Israeli cohort study found obesity to be almost twice as common in adolescents with severe ADHD (13.5%) as in those without, and about 30% more common in those with mild ADHD than in those without.⁷

A meta-analysis of 42 studies with n = 728,136 participants found:⁸
Obesity increases the risk of ADHD in children by 20% (OR = 1.20) and in adults by 55% (OR = 1.55)
ADHD increases the risk of obesity in children by 40 % (10.3 % compared to 7.4 %) and in adults by 70 % (28.2 % compared to 16.4 %)

A study of n = 450,000 Europeans found that single nucleotide polymorphisms that cause obesity also causally increase the risk of ADHD, depression and bipolar Disorder.⁹

ADHD is a significant risk factor for the development of obesity.¹⁰ Impulsivity in ADHD and increased BMI share genetic and neurophysiological correlates.¹¹ ADHD, alcohol dependence, insomnia and heavy smoking correlate with increased body fat.¹²
Attention problems and hyperactivity correlated positively with response to food, emotional overeating, the desire to drink and a slowing down of eating. Attention problems reduced the enjoyment of food. Conversely, eating behavior does not appear to be causative of ADHD.¹³ Normal overweight (below obesity) is also not thought to increase the likelihood of ADHD.⁶

A long-term cohort study in the USA found a linear correlation between the number of ADHD symptoms and the factors waist circumference, BMI, obesity, diastolic blood pressure and systolic blood pressure.¹⁴ An Israeli study also points to this.¹⁵
The comorbidity of ADHD was 58% in a study of extremely overweight children treated as inpatients.¹⁶
Among 155 adult women in Brazil with a BMI > 39, an ADHD rate of 28.3% was found. Binge eating, bulimia and depression were also above average.¹⁷ The likelihood of ADHD was thus 6.4 times higher than the prevalence of 4.4% expected in adults.
The body mass index of people with ADHD is also above average.¹⁸

A minority of studies found no association between ADHD and BMI. One study found no association of ADHD with BMI at age 9 or 13. However, children with ADHD at age 9 were significantly more likely to be overweight/obese than children without ADHD. However, this had not been due to ADHD but to other child and parental factors such as female gender, little exercise, overweight/obese parents and prenatal smoking during pregnancy.¹⁹ A smaller study found no overlap between obesity and ADHD or autism spectrum disorders in 76 adolescents.²⁰ Another study found no correlation between ADHD and high BMI, but did find a correlation between unhealthier eating habits and ADHD in adolescents.²¹

A meta-analysis found an ADHD prevalence of between 1.6% and 18% in persons with ADHD. Comorbid ADHD was more common in the AN binge-eating/purging subtype and in the bulimia subtype than in the restrictive anorexia subtype.
Among persons with ADHD, the meta-analysis found an eating disorder lifetime prevalence ranging from zero to 21.8% among women with ADHD.²²

1.2. ADHD treatment works against obesity¶

ADHD treatment can result in surprising weight loss success in massively overweight patients. The ADHD-positive diagnosed obese patients lost over 12% weight per year under typical ADHD medication.²⁵
For comparison: according to the current standard, treatment for obesity is successful if the weight gain does not exceed 5% per year.

Other studies also report a decrease in excessive BMI as a result of ADHD treatment in people with ADHD.²⁶

1.3. Stomach reduction less effective for ADHD symptoms?¶

One study found reduced weight loss after stomach reduction in those people with ADHD with emotional dysregulation, a core symptom of ADHD.²⁷

1.4. Obesity and addictive behavior¶

Around half of all overweight people who have had a stomach reduction subsequently develop another addiction. This is impressive proof that obesity can be a consequence of addiction.²⁸²⁹³⁰

It is well known that ADHD causes a massive Disorder of the reward system, with the Consequences that rewards that are further away are significantly less interesting compared to non-affected people. Food can provide this instant gratification.

2. ADHD and eating disorders¶

Eating disorders occur 3.6 times more frequently in girls with ADHD than in those not affected.³²

Leptin is an adipokine produced by adipose tissue that is a hormone involved in controlling feelings of hunger and satiety.³³
A significantly reduced serum leptin level was found in children with ADHD, independent of MPH intake³⁴

Ghrelin (Growth Hormone Release Inducing) is an appetite-stimulating peptide that is produced in the gastric mucosa and the pancreas.
In children with ADHD, serum ghrelin levels correlated with auditory attention and increased in a dose-dependent manner with MPH administration, but were decreased with MPH side effects³⁴

One study found an increased risk of ADHD:³⁵

• Binge eating: OR=13.2 (1320 %)
• Bulimia nervosa: OR=27.5 (2750 %)
• recurrent binge eating: OR 5.8 (580 %)

However, the increase in risk was no longer significant after taking depression, anxiety, alcohol consumption and impulsivity into account:
Since impulsivity is an ADHD symptom, we believe that adjusting for this falsifies the result. If study results on ADHD were then adjusted for attention problems and hyperactivity/impulsivity, there would inevitably never be any significance remaining.

Another study found that ADHD increased the risk of eating disorders by 97% (HR 1.97) and ASD by 183% (HB 2.82). This study also found that anxiety and depression could be responsible for 44% to 100% of the association between ADHD or ASD and eating disorders.³⁶

2.1. Binge eating twice as often¶

Eating disorders such as binge eating (very roughly: binge eating without vomiting) are also suspected to correlate with ADHD and contribute to weight problems.³⁷³⁸

In obese patients (BMI > 30), ADHD doubles the likelihood of binge eating and increases the likelihood of other eating disorders.³⁹

Among 150 adult women with a BMI over 39, an ADHD rate of 28.2% was found. Binge eating, bulimia and depression were also above average.¹⁷

2.2. Bulimia 6 to 8 times more common in women with ADHD¶

Bulimia (bulimia nervosa; very roughly: binge eating with vomiting) is found in 11% to 12% of adult women with ADHD (according to DSM-III-R criteria) compared to around 1% to 3% of women without ADHD. There are no differences between men and children.⁴⁰ Assuming a 1.5% prevalence of bulimia nervosa⁴¹, this would result in an 8-fold increase in the frequency for women with ADHD.
A meta-analysis reported that almost all studies reported a positive effect of stimulants on eating behavior in bulimia nervosa.⁴²

2.3. Anorexia is 2.2 times more common with ADHD¶

The probability of girls and women with ADHD suffering from anorexia (very roughly: striving for extreme thinness) is “only” 2.2 times higher than for girls and women without ADHD.⁴³

2.4. Compulsive grazing (snacking) increases the risk of ADHD by 8 times¶

Grazing is the unstructured, repetitive eating of small amounts of food over an extended period of time outside of planned meals and snacks and/or not in response to feelings of hunger or fullness. There are two subtypes of grazing:

• compulsive grazing
  • Feeling that you cannot resist or stop grazing
  • Population prevalence 10.2 %
  • ADHD prevalence among people with ADHD approx. + 800 % (OR 8.94)⁴⁴
  • correlates with
    • stronger psychopathology of the eating disorder
    • increased psychological stress
    • lower psychological quality of life
    • lower treatment success in patients with high body weight
• non-compulsive subtype
  • i.e. repeated, distracted eating
  • Population prevalence 38 % to 90 %

3. ADHD and diabetes¶

Of 677,587 German children and adolescents, 16,833 were diagnosed with ADHD (2.5 %), while 3668 were treated with insulin for type 1 diabetes mellitus (0.05 %). In the subgroup of people with ADHD, 153 children (4.2%) also had an ADHD diagnosis. This suggests that people with ADHD have a greatly increased prevalence of type 1 diabetes and vice versa.⁴⁵

4. Cortisol, metabolism and body fat¶

Glucocorticoids (such as cortisol) play a central role in the regulation of carbohydrate metabolism by influencing gluconeogenesis.⁴⁶

Glucocorticoids also initiate and regulate a large number of digestive enzymes⁴⁷, the expression of membrane-bound transporter proteins⁴⁸, and proteins that are significantly involved in gluconeogenesis.⁴⁹

• Cortisol increases the success of pleasurable or compulsive activities (intake of sucrose, fat and drugs or cycling). This motivates the intake of “comfort food”.⁵⁰
• Cortisol systemically increases the fat deposits in the abdomen. This causes⁵⁰
  • Inhibition of catecholamines in the brain stem and
  • Inhibition of CRH expression in the hypothalamus, which consequently inhibits ACTH
• Cortisol acts on the fatty tissue via insulin⁵¹
  Possible Consequences:
  • Visceral obesity⁵¹
  • Insulin resistance⁵¹
  • Dyslipidemia⁵¹
• Cortisol increases adrenaline-induced lipolysis (fat splitting, fat digestion).⁵²⁵³
  The impairment can be exacerbated by reduced ACTH levels.⁵⁴
  It is possible that this correlation is reversed in severely overweight people (see below).
• While chronic stress and high glucocorticoids increase body weight gain in rats, in humans this causes either increased food intake and weight gain or decreased food intake and weight loss.⁵⁰⁵⁵
• Several studies show a correlation between the cortisol stress response and the waist-to-hip ratio, so that a low cortisol stress response is associated with a low waist-to-hip ratio (less pronounced waist), while a high cortisol stress response is associated with a high waist-to-hip ratio (pronounced waist).⁵⁶⁵⁷⁵⁸
• Abnormalities of fat metabolism (hypertriglyceridemia), which occur more frequently in the type A personality, can be eliminated by ACTH administration, but not by cortisol administration.⁵⁹
  The described ACTH effect would be consistent with this hypothesis of an underreactivity of the HPA-A axis in type A.
  In people with ADHD type A (then: ADHD-HI = with hyperactivity), a genetic predisposition or permanent stress could be the cause
  → have led to a long-lasting increased release of CRH,
  → which triggers CRH receptor downregulation,
  → which causes underactivation of the pituitary gland,
  → which triggers a reduced release of ACTH,
  → which causes reduced adrenal gland activity,
  → which results in a reduced release of cortisol,
  → which is why only the MR receptors, but not the GR receptors, are addressed when the HPA axis is activated at the end of a stress response,
  → which means that the HPA axis is not switched off properly.
• The noradrenaline level in the OFC and in the amygdala correlates with the activation of the HPA axis in healthy people. In severely overweight people, however, this correlation is inverted.⁶⁰
  The endocrine stress responses of noradrenaline and cortisol run in parallel. In ADHD-HI (with hyperactivity), not only the cortisol stress response but also the noradrenaline stress response is reduced.
• Obesity is characterized by high oxidative stress and inflammation.⁶¹ Inflammation is inhibited by cortisol. A low cortisol stress response results in reduced inhibition of inflammation.

5. Links between ADHD and eating disorders¶

5.1. Emotional dysregulation and impulsivity¶

An important link between eating disorders (especially binge eating) and ADHD appears to be the symptoms of emotional dysregulation and impulsivity.⁶²

5.2. Dopamine¶

Both ADHD and obesity are characterized by deviations in the dopamine balance.⁶³ While disordered eating behavior in women correlated with an increased plasma dopamine level, the blood dopamine level was reduced in men with eating disorders.⁶⁴