Obese adults who find themselves on the losing side of the battle of the bulge could also be suffering from attention deficit hyperactivity disorder (ADHD) according to a new Canadian study.

Researchers at the Centre for Addiction and Mental Health and the University of Toronto set out to determine whether the condition plays a role in why some obese people have such a hard time sticking to weight loss programs.

"A substantial number of obese clients exhibited consistent difficulty keeping an accurate diet record, planning and preparing meals, eating regularly, and maintaining an exercise schedule. While there are numerous explanations for such behaviour, we began to consider the possibility that perhaps, for some, it might be related to an underlying neurological condition; attention deficit hyperactivity disorder," speculated researchers J.P. Fleming and colleagues in a study published in the journal Eating and Weight Disorders.

In order to test the theory, the researchers administered a series of standardized ADHD tests to 75 women who had been referred to an obesity clinic. The women had an average age of about 40 and an average Body Mass Index (BMI) of about 43, which is considered severely obese. The tests included a rating of current ADHD symptoms as well as a retrospective self-report of symptoms experienced during childhood.

When comparing the results to those of the general population, the researchers found that 26.6% of the obese subjects could be classified as having ADHD. Among the general population, 3% to 5% of adults are considered to have the condition, which is characterized by an inability to focus or concentrate on tasks, impulsive behaviour, difficulty with social relationships, disorganization, fluctuating mood, and poor work performance. In children, the condition is often coupled with hyperactivity, though this is less common when ADHD occurs in adults.

"While the current study does not allow us to ascertain the cause of the deficit, it is striking that a very high percentage of this sample of severely obese women report very substantial problems with the set of symptoms that we classify as reflecting ADHD," wrote the researchers.

Noting that their research was limited by the lack of a control group and by the fact that the diagnosis of ADHD was established using self reports, the researchers said further research needs to be done to explore the link between obesity and ADHD.

"It is well established that both adults and children with ADHD have very high rates of comorbid disorders including depression, anxiety, sleep disorders and substance abuse. … It is possible that in the same way that ADHD undermines the regulation of emotions, sleep, and moderate alcohol use, it may disrupt dietary regulation."

The authors also speculated that the high rates of symptoms related to ADHD could also be caused by other factors, such as depression or a sleep disorder.