These findings, published in Pediatrics, may be surprising to parents because drugs such as Ritalin or Adderall used to treat ADHD can suppress appetite, said Dr. F. Xavier Castellanos, the study co-author and a professor of child and adolescent psychiatry at New York University.

“It’s not uncommon for kids treated with ADHD medications to be fairly thin,” Castellanos said. Because parents often worry that thinner boys won’t grow as tall, “sometimes [they] will encourage their boys to eat more.”

Instead, to help avert weight problems down the road, parents should be alert to poor eating habits. “If anything, you have to pay attention to how many times they’re having fast food, how many times they’re having fried food, whether they’re getting meals supersized,” Castellanos said.

The study comes at a time when ADHD rates are rising. A new report from the Centers for Disease Control and Prevention found that ADHD is the most common mental health issue in children ages 3-17, with nearly 7 percent of kids receiving a diagnosis.

The NYU researchers followed 222 boys — 111 with ADHD and 111 without, for an average of 33 years — hoping to better understand the disorder’s effects on the brain. The boys with ADHD, all from middle-class, white families, were diagnosed between the ages of 6 and 12.

Decades later, when some of the men returned for brain scans, many of the now 40-something adults who had ADHD as children had gained so much weight they barely fit into the fMRI machine, Castellanos said.

Denying certain foods to children or pressuring them to eat every bit of a meal are common practices among many parents. But researchers at the University of Minnesota found parents who restricted foods were more likely to have overweight or obese children. And while those who pressured children to eat all of their meals mostly had children of normal weight, it adversely affected the way those children ate as they grew older, according to the study published Monday in the journal Pediatrics.

Investigators combined data from two separate research studies. The first, EAT 2010 (Eating and Activity in Teens), studied around 2,800 middle and high school students from public schools in Minneapolis and St. Paul, Minnesota. Participants in the project responded to survey questionnaires designed to examine dietary intake and weight status.

Researchers combined that data with information from the Project F-EAT (Families and Eating and Activity Among Teens), a study designed to examine factors within the family environment on weight in adolescents.

From the combined information, researchers were able to gain a better understanding of how parents’ approach to food and feeding is related to adolescents’ weight. According to the Centers for Disease Control and Prevention, obesity now affects 17% of all children and adolescents in the United States – triple the rate from just a generation ago.

“We found that between 50 and 60% of parents from our sample reported requiring that their child eat all of the food on their plate at a meal,” said researcher Katie Loth, the study’s lead author. “Further, we found that between 30-40% of parents from within our sample reported encouraging their child to continue eating even after their child stated that they were full.

“While these pressure-to-eat behaviors were more frequent among parents of non-overweight adolescents, they were still endorsed quite frequently by parents of overweight and obese adolescents, indicating that many parents endorse these behaviors regardless of their child’s current weight status,” she said.

“There’s a lot of other evidence out there to continue to support breast-feeding,” says the study’s lead author Dr. Richard Martin, a professor of clinical epidemiology at the University of Bristol in the U.K. “But in terms of breastfeeding reducing obesity, it’s unlikely to be effective.”

Martin worked with colleagues at Harvard University and McGill University in Montreal to assess 15,000 mothers in Belarus. The location was intentional — when the study began in 1996, breastfeeding was not a popular practice among Belarusian mothers. By separating the moms-to-be into two groups — one that gave birth at hospitals where staff received “Baby-Friendly” training designed to encourage breastfeeding, while the other delivered at hospitals that provided no extra support for the practice — researchers were able to create a “huge contrast” in a setting where breastfeeding rates were historically low. After three months, 43% of babies in the first group were exclusively breastfeeding compared to just 6% in the group that were born in hospitals that had no extra training.

The babies were followed up in 1997 — their first year of life — and again when they reached 6 ½ and 11 ½. The breastfed babies experienced fewer gastrointestinal infections, less eczema and higher IQ (they scored about 7 ½ points higher than their formula-fed friends at age 6 ½). There was no difference in dental cavities, allergies, asthma or rates of being overweight or obese.

The latest report, published in the Journal of the American Medical Association (JAMA) marks the first release of data from the 11 ½-year old participants. Mirroring the earlier results, the researchers found no changes in weight and body fat between those who were breast-fed and those who weren’t. About 15% of the children in both groups were overweight, and 5% were considered obese.

Comparing body mass index (BMI) or measures such as waist circumference and skin thickness yielded “absolutely nothing that was statistically significant,” says Martin.

The researchers found that, out of the 15 food types in the questionnaire, only fast food showed an association with asthma and eczema in both age groups regardless of gender and socio-economic status. Three or more servings a week was linked to a 39 percent increase in severe asthma among teens and a 27 percent increased risk among younger children.

“A consistent pattern for the adolescent group was found for the relationship between symptoms and fast foods,” the researchers wrote in the study. “As adolescents are generally known to be high consumers of fast food, these results that show a significant increased risk of developing each or all three conditions may be a genuine finding.”

Though both eczema and asthma can be triggered by food allergies—and typical fast-food meals are filled with common allergens like gluten, dairy, egg, and soy—Williams told Yahoo! Shine that allergies probably aren’t the main issue here.

“We did not look for gluten, although bread and pasta both have gluten (however gluten free pasta and bread are now widely available so when someone says yes to eating bread 3x per week it may well be that they ate gluten free as this practice is growing in some countries). So we cannot tease this out,” he wrote in an email. “There is no doubt that food allergy plays an important role in some people with severe asthma and eczema, but those people tend to recognize it and avoid those foods.”

“I doubt if our observation of an association between severe allergies and fast foods is mediated much by increased food allergens,” he added.

A 2011 study published in Nutrition Research and Practice suggested that additives in processed foods could also trigger an allergic reaction in some kids, but Williams and his team say that fat intake, not food allergies or additives, is probably the main culprit.

In the study, published in the journal Pediatrics, the researchers analyzed data from 217 African-American mother and infant pairs from the Infant Care and Risk of Obesity Study. At 3, 6, 9, 12, and 18 months after birth, the infants’ mothers reported on their babies’ temperament—how fussy or complacent they were—as well as their own TV viewing habits, including how long the TV was on during the day and how often they fed their babies while watching TV. Overall, mothers spent a significant amount of time watching television, and reported that they spent quite a bit of time feeding their infants in front of the TV as well. Infants just 3 months old were exposed to an average of nearly three hours of TV or videos daily, and nearly 40% of the youngsters were exposed to three hours of TV every day by the time they were a year old.

More active and fussier infants were more likely to spend extended periods of time in front of the TV. The exposure was also higher among obese mothers, especially those with the fussier kids, leading the researchers to suggest that the television may serve as an easy entertainment strategy.

The scientists were also able to find some factors that contribute to fewer hours in front of the screen, however. Moms with a high school diploma or any additional education were less likely to have TVs in their infants’ room, and less likely to keep the television on during meals.

“In the last decade or so there has been a lot of attention paid to parenting style and care giving. One component has to do with feeding and focus placed on the feeding environment,” says Margaret E. Bentley, Associate Dean of Global Health at the University of North Carolina at Chapel Hill’s Gillings School of Global Public Health and the principal investigator of the study. “Half of the time, infants are being fed with the television on, which is a feeding strategy we do not recommend.”

Eating in front of the television can lead to unhealthy dining habits that linger into childhood and adulthood, Bentley and her colleagues say, since mothers feeding infants while watching TV might be distracted and not as alert to subtle cues babies send when they feel full, which can lead to overfeeding.