New Research: Childhood Obesity Linked to ADHD, Impulsivity

November 21, 2024

Children with ADHD are more likely to be obese, despite lower-than-average birth weights, according to a new study that found a correlation between elevated ADHD symptoms and higher body mass index (BMI) scores for both females and males. ¹The study, published in the Journal of the American Academy of Child & Adolescent Psychiatry, complements additional research tying ADHD impulsivity to unhealthy food consumption and overeating.

In analyzing data from the Millennium Cohort Study (MCS) of more than 19,000 families with children born between 2000 and 2002, researchers found that children with ADHD had significantly lower birth weights than did children in the control group. Both groups maintained similar obesity rates until age 5, when the ADHD group experienced a rise in obesity that continued throughout adolescence.

“As children with ADHD are typically lighter in weight at birth than children without ADHD, the results suggest there may be a sensitive time period between the ages of 3 and 5 years during which this association reverses, and higher ADHD symptoms become associated with obesity,” the researchers wrote.

Researchers collected data when the 442 ADHD cohort members reached 9 months and 3, 5, 7, 11, 14, and 17 years. (The study excluded cohort members taking ADHD medications.) They found that weight gain began earlier for girls with ADHD (age 7) compared to boys with ADHD (age 11). “The weight changes in girls additionally seemed to be more long-lasting, whereas the observed changes in boys seemed to be transitory,” the researchers wrote. It is unclear whether these associations continue into adulthood.

Further analysis revealed that elevated ADHD symptoms in females at ages 7, 11, and 14 predicted higher body mass index (BMI) scores at ages 11, 14, and 17, respectively. The same association occurred in males at ages 11 and 14. These results suggest that ADHD symptoms are not entirely responsible for the uptick in weight children experience between the ages of 3 and 5 years.

Genetics, Prenatal Factors Impact BMI

Hormones and puberty contribute to weight gain. “Sometimes pre-teens can gain weight as the body prepares for a growth spurt in height,” says Roberto Olivardia, Ph.D., clinical psychologist at Harvard Medical School. “Therefore, BMI normalizes as they gain height.”

Prenatal factors, including the mother’s pre-pregnancy BMI, prenatal blood pressure, smoking during pregnancy, and poor nutrition, predicted a higher BMI at 5 years. Genetics may also increase the risk of obesity.

“It is possible that there is a common genetic background to both ADHD and [being] overweight or, as parents with ADHD are more likely to have children with ADHD, this may have an impact on executive function skills involved in parenting, such as planning healthy meals, which in turn may influence weight status,” the researchers wrote. “Parents with an increased genetic risk may be influencing their child’s home environment in ways that compound inherited risk.” ², ³

Impulsivity Linked to Poor Dietary Decisions

Another recent observational study found a strong link between impulsivity, a common ADHD trait, and unhealthy food consumption and overeating, specifically in the form of snacking. ⁴

The study, published in the Journal of Attention Disorders, analyzed data from the KOALA Birth Cohort Study of 810 adolescents aged 16 to 20 years. The researchers identified five dietary patterns

• Snack — high intakes of regular (non-diet) soft drinks, fruit juice/drinks, fried snacks, chips, nuts or snacks, and energy drinks
• Healthy — high intakes of lettuce, raw vegetables, fruit, eggs, and tea
• Animal-based — high intakes of animal dairy products, meat and chicken, and fish
• Sweet — high intakes of pastry, chocolate bars, candy bars, cake or biscuits, and sweets
• Beverage — high intakes of diet soft drinks, light fruit juice/drinks, sports drinks, and energy drinks

Among the five dietary patterns, adolescents with an ADHD diagnosis scored higher on the Snacking dietary pattern than did those without ADHD. Higher Snack scores were associated with difficulties with cognition, inattention, and impulsiveness. Impulsivity was inversely related to Sweet dietary patterns and positively related to Beverage dietary patterns.

Interestingly, adolescents with ADHD appeared no less likely than their neurotypical peers to engage in Healthy dietary patterns. “The lack of a reverse association between ADHD symptoms, especially impulsivity, and the healthy pattern is unexpected and raises questions,” the researchers wrote.

Though the study does not prove causality, the findings suggest that eating habits may differ based on the specific ADHD symptoms each individual experiences.

“When studying how ADHD impacts an adolescent’s diet, looking beyond a simple diagnosis and considering the specific dimensions of their ADHD symptoms, like inattention, hyperactivity, and impulsivity, provides a more nuanced understanding of their dietary behaviors, as these individual dimensions can differentially influence food choices and eating patterns, even among individuals with the same ADHD diagnosis,” the researchers wrote.

Both ADHD and high BMI are associated with poor health outcomes, including asthma, diabetes, and cardiovascular disorders, so it’s vital that children understand the potential consequences of their dietary decisions. ⁵,⁶

Adolescents have more independent access to food, which can also result in unhealthy choices when impulsivity collides with puberty. “Parents have less control over what teenagers eat since they are not always with them,” Olivardia says, “and this most likely plays a bigger role in weight gain.”

Preventing Childhood Obesity

Educating children about their food choices can help curb unhealthy food cravings. For example, instead of banishing carbs from your kitchen, Olivardia says, explain them in a way children can understand. “Say, ‘Simple carbs, like potato chips, taste good, but basically break down in the body as sugar. There is no nutritional value in simple carbs, and they get in the way of healthy weight, high energy, and other things that matter, like your complexion.’”

Caregivers can help children and adolescents make better dietary decisions by incorporating the following strategies:

• Set up a “food environment” that promotes healthy eating. Children with ADHD may not notice they’re hungry until they’re starving. To fend off unhealthy pantry raids, stock up on nutritious, easy-to-grab meals and snacks that require little preparation, such as peanut butter crackers, yogurt, or string cheese. Display healthy snacks and fruits in plain view in the refrigerator or pantry.
• Practice good sleep hygiene. In addition to regulating hormone levels, a good night’s sleep makes it less likely that children will turn to food for comfort in fragile moments.
• Set healthy eating rules. Create family eating rules that encourage children to eat attentively — for example, no eating while watching T.V. or eating straight out of the bag. Consider requiring children to eat only in the kitchen or dining area.
• Teach children mindful eating skills. Children are less likely to overeat when they practice mindful eating. Teach children to put down their fork in between bites. Or ask them to describe what they’re eating as though the person listening has never tasted that food.
• Set a good example. Children learn by watching others, especially their parents. Set a good example by making smart food choices, dishing appropriate portions, and not distractedly eating while engaging in another activity (like using your phone).
• Treat ADHD. Make sure children adhere to their ADHD treatment plan. ADHD stimulant medications help children better observe and regulate their behaviors and avoid impulsive eating. They also make it easier to follow through with healthy eating and exercise plans.

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