Family Matters: Exploring Risks for Obesity in Autism

Why are children and adults with autism more likely to be obese than other people?^1-3 Studies show that many have extremely picky eating habits, do not exercise as much as others, or take medications that cause weight gain.^4-11 While those may affect weight, a new study says the biggest risk factor, at least for youth, has nothing really to do with autism: it’s families.¹²

Youth whose sisters and brothers were obese had almost three times the odds of being obese, according to a study of 1,791 children and teenagers with autism.¹² Having an obese mother doubled the odds, while an obese father increased odds by 1.5 times. This is similar to patterns in the general population, explained the study, from the Journal of Developmental & Behavioral Pediatrics. Whether someone has autism or not, his genetics, lifestyle, access to healthy foods, and eating habits play a large role in his weight.

Interestingly, having an obese sibling poses a higher risk than having an obese parent. That may be because brothers and sisters share the same food and exercise opportunities in two places: home and school. “Are they sharing a school where there are a lot of vending machines, or school lunches with desserts or sugary drinks?” asked Jack R. Dempsey PhD, the study’s lead author. “Do they live in a community with no area where they can play outside?”

Previous studies have investigated risks for obesity in autism, but they did not fully explore family influences. Those family factors are “one the most powerful predictors of weight in the general population,” explained Dr. Dempsey, a child psychologist at Texas Children’s Hospital. He and his fellow investigators used data from the Simons Simplex Collection (SSC) research project, which made it easier to study family factors. The SSC project contains data on mothers and fathers, and their biological children, one of whom has autism. SSC researchers had collected the weights and heights of all family members, along with details about children’s autistic behaviors, language, development, and genetics.

Defining Obesity – and Why it Matters

Dr. Dempsey said his team chose to study weight for several reasons. “Children who become obese will have less successful health outcomes and will be more at risk for a variety of illnesses,” he said. Obesity increases the risk of heart disease, diabetes, high blood pressure, sleep apnea and high cholesterol, according to the U.S. Centers for Disease Control. For adults, obesity means having a Body Mass Index (BMI) of 30 or higher, which is calculated based on a person’s height and weight. For example, someone who is 5 feet, 5 inches tall (165 cm), and 180 pounds (81.65 kg), has a BMI of 30. In children, a BMI calculation includes height, weight, age and sex. (See below for links to BMI calculators.)

Dr. Dempsey’s team also wanted to conduct research that could lead to better treatments. Knowing all the predictors of obesity in autism spectrum disorder (ASD) gives healthcare providers a better understanding of how to treat it, he said.

Logan Wink, a psychiatrist and researcher who was not involved in the study, said, “As a clinician, it doesn’t surprise me at all that there is likely a correlation between siblings and parents, and their dietary and lifestyle habits.”

To be sure, other influences come into play, and Dr. Dempsey’s team looked at those, too.

Other Influences on Obesity in Autism

The team found that taking antipsychotic and mood stabilizing medications almost doubled the odds of obesity in these youth. Previous studies, including one by Dr. Wink, have shown that newer antipsychotic medications, such as aripiprazole (brand name Abilify) and risperidone (brand name Risperdal), are associated with significant weight gain.^10,11,13-17 Doctors often prescribe antipsychotics to people with autism for “irritability,” typically self-injury and aggression. One in five or six youth with autism has taken them, along with 43 percent of adults on the spectrum.^18-20

Youth with significant symptoms of depression or anxiety, or bodily complaints such as stomach aches, had 1.5 times the odds of being obese, according to Dr. Dempsey’s team. Being an older teen and having poor daily living skills increased risk slightly.

Interestingly, a common symptom of autism, repetitive behaviors such as hand-flapping or finger-flicking, did not affect a child’s weight. Researchers had wondered if repetitive behaviors might be related to picky eating. Many children with autism refuse to eat a variety of foods, such as fruits and vegetables. They often prefer foods that are beige or brown, Dr. Dempsey said. That habit could lead to weight gain if a child will only eat high-calorie foods. But this analysis did not find a link to repetitive behaviors.

The more risk factors a child has, the greater the odds of being obese, Dr. Dempsey said. For example, an older child taking antipsychotic medication with obese parents and an obese sibling would have a significantly higher risk than a child who did not have those characteristics.

Focusing on Helping the Family

The researchers recommended family-centered treatment to help combat obesity in youth with autism. “At least 1 portion of such family-centered treatment should focus on the stress of having a child with ASD and focus on finding ways to be active together and cope with stress without eating,”¹² the study said.

Many youth with autism have behaviors that could complicate family activities and outings for exercise. For example, nearly half of children with autism wander or run away from caregivers, according to an Interactive Autism Network study.²¹ Caregivers may face special safety challenges when taking children with those behaviors for walks or recreational activities.

How do Families in the SSC Project Compare to Others?

The SSC research project offered researchers a wealth of data in which to study weight, but they acknowledge that the SSC families may have been at lower risk of obesity than the general population. That is because those families mostly had moderate to high socioeconomic status, which “is almost certainly a protective factor” against obesity, the study said.¹²

Obesity affected 17.5 percent of the children with autism in the SSC study,¹² compared to 17 percent of youth in the general population.²² A smaller number – 13 percent – of the SSC siblings were obese.¹² SSC fathers had an obesity rate of 38 percent,¹² four percentage points higher than all American men.²² But SSC mothers had a lower obesity rate than other women, 29 percent to 38 percent.

Previous studies found that obesity affected 18 to 30 percent of children and teens with autism.^3,23 The study that found a 30 percent obesity rate in autism also found a higher rate, 23 percent, among all American children ages 3-17, using data from 2003 to 2004.²³