Unhealthy Diet Raises Heart Risk for Obese Teens

Study Shows Obese Teens Don't Eat Enough Vegetables, Dairy, and Fiber

Medically Reviewed by Laura J. Martin, MD on March 22, 2011

March 22, 2011 -- Obese teens don’t have enough fresh produce, dairy products, or fiber in their diets and may be more likely than normal-weight teens to develop heart and other health problems, new research indicates.

This doesn’t mean they don’t feel well as youngsters, but that their diets aren’t good for long-term good health.

Researchers analyzed blood tests of 33 obese youths between 11 and 19 and compared the results to those of 19 normal-weight youngsters in the same age group.

Dietary quality was deemed poor in all study participants. The obese teens had about the same daily intake of calories, grain, protein, and fat servings, but significantly fewer portions of dairy, fruit, and vegetables.

Poor Diet Leads to Poor Health

Among the key findings of the study:

  • Blood analysis showed insulin resistance, a precursor to type 2 diabetes, was greater in obese youngsters. When insulin resistance occurs, greater levels of insulin are needed to keep blood sugar levels normal.
  • Obese teens had almost 10 times greater levels of a substance called C-reactive protein, which causes inflammation throughout the body. Inflammation is a leading cause of many diseases, including heart disease.
  • The levels of an amino acid called homocysteine -- shown to be related to the development of blood vessel and heart disease -- were 62% higher in obese youngsters than in those of normal weight.
  • The blood of obese teens showed more signs of oxidative stress that leads to inflammation, and an increase in blood vessel damage and stiffening.

“The metabolic abnormalities suggest that the process of developing heart disease has already started in these [obese] children, making it critical for them to make definitive lifestyle and diet changes,” says senior study author Ashutosh Lal, MD, of Children’s Hospital and Research Center in Oakland, Calif.

In the study, obesity was defined as having a body mass index (BMI) higher than the 95th percentile of children the same age. Normal weight was defined as having a BMI below the 85th percentile.

Diets of Obese Teens vs. Normal-Weight Teens

“Looking at the numbers you would think these children might feel sick, but they did not,” Lal says. “They are apparently feeling well, but there is a lot going on beneath the surface.”

In all youngsters tested, obese and normal-weight kids alike, dietary quality was deemed poor -- low in fresh produce, fiber, and dairy products. The obese and normal-weight children reported on questionnaires that they ate similar amounts of grains, proteins, fats, and total calories.

But the obese young people reported significantly fewer servings of dairy products and tended toward fewer fruit servings. Their diets also were lower in vitamin C, vitamin D, potassium, and vitamin A, which are found in fortified dairy products and deeply colored fruits and vegetables.

The researchers say doctors should pay more attention to what young patients are eating, given that dietary quality was low in youths of normal weight and those who were obese.

“Obese teens were consuming too few of the natural sources of antioxidants, fruits, and vegetables and may have increased antioxidant needs based on the inflammation associated with their extra adiposity [body fat],” Lal says. “For their heart health, obese teens need to eat better, not just eat less.”

The research is being presented in Atlanta at the American Heart Association’s Nutrition, Physical Activity and Metabolism/Cardiovascular Disease Epidemiology and Prevention 2011 Scientific Sessions.

Show Sources


News release, American Heart Association.

American Heart Association’s Nutrition, Physical Activity and Metabolism/Cardiovascular Disease Epidemiology and Prevention, 2011 Scientific Sessions, March 22-25.

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