Obesity

Obesity is one of the major public health problems of this century. A study published in April 2016 in the prestigious journal The Lancet conducted in 19.2 million participants from nearly 200 countries indicate that by 2025, global obesity prevalence will reach 18% in men and surpass 21% in women . In 2013 the prevalence of obesity exceeded the 50% of the adult population in some countries from Oceania, North Africa and Middle East. Lower but still alarmingly high prevalence was observed in North America (~30%) and in Western Europe (~20%). These figures are of serious concern due to the strong link between obesity and different diseases, and particularly with cardiovascular disease. It is well-known that obesity worsens most of the cardiovascular disease risk factors, such as plasma lipids, blood pressure, glucose and inflammation. Obesity increases also the risk of cancer. Finally, there is evidence supporting that obese people do not only have a worse physical health, but also a worse mental health. Bidirectional associations have been reported between obesity and depression, and between obesity and anxiety (Mannan et al., 2016), among other mental disorders.

Obesity and ADHD

These bidirectional associations between obesity and mental health can be extended to ADHD. A recent meta-analysis has highlighted a significant and positive association between ADHD and obesity. Authors reported  that prevalence of obesity was increased by about 70% in adults with ADHD (28.2%) compared with those without ADHD (16.4%), and by about 40% in children with ADHD (10.3%) compared with those without ADHD (7.4%), which support that the notion of obesity and one of the most common comorbidities of ADHD.

Potential Mechanisms linking obesity and ADHD

Two key symptoms of ADHD are inattention and impulsivity, and both might  increase the risk of developing obesity. In addition, the reward system deficiency suggests that ADHD is due to insufficient brain dopamine. Inattention could diminish the individual’s sensation of satiation or lead to irregular eating patterns. In addition, individuals with ADHD are more prone to mood instability. This instability could result in a higher consumption of high caloric foods for pleasure. The second symptom, impulsivity could contribute to obesity by means of disordered eating patterns, both in quantity and quality. This hypothesis is supported by: 1) binge eating behaviour, uncontrolled by the characteristic impulsivity of ADHD, could compensate the dopamine deficiency associated with ADHD; 2) stimulant medication reduces impulsivity and supresses appetite.

In summary, obesity has reached epidemiological proportions in most of developed counties, which is a major public health concern due to its link with physical and mental health. In addition, obesity seems to be more prevalent in ADHD patients than in age-matched controls, which seems to be explained by a number of mechanisms linking ADHD to obesity.