American kids are getting heavier. Too much extra weight puts kids, and adults, at risk for dangerous diseases. But a new study reveals some good news. Kids are showing signs of improvement in key markers of a potentially serious condition known as metabolic syndrome. Better food choices likely triggered this change, new data suggest.

Metabolic syndrome is a group of symptoms that, taken together, mark people at high risk of heart disease and diabetes. This syndrome used to show up when adults got fat. Today, many kids develop the syndrome, too.

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The syndrome can emerge when people eat too much sugar and don’t get enough exercise. Weight gain is the most obvious symptom. But other invisible issues also develop, which serve as red flags that something is wrong. These include obesity, high blood pressure, high blood sugar, high levels of bad fats and low levels of good cholesterol. Three or more of these issues will lead to a diagnosis of metabolic syndrome.

Mark DeBoer is a doctor and medical researcher at the University of Virginia Health System in Charlottesville. He and his colleagues wanted to track signs of metabolic syndrome in U.S. teens. They took a look at the health of 5,117 adolescents over a time period spanning 1999 to 2012. The Centers for Disease Control and Prevention, or CDC, in Atlanta, Ga., had gathered the information on these kids, aged 12 to 19. CDC regularly surveys people about their health. The data they collect give researchers a picture of the overall health of people throughout the United States.

Over the 13-year span studied, teens got increasingly heavier. But surprisingly, the total amount of food they ate dropped somewhat. At the same time, other aspects of teen health improved. In 2012, teens had lower levels of bad fats, also called triglycerides, than in 1999. They also had higher levels of good cholesterol. “This likely means that there is a slight decrease in the risk of future disease in this age group,” concludes DeBoer.

His team’s study appeared February 9 in Pediatrics.

What changed over the studied period? Teens in the later years were eating less sugary food. They also ate more unsaturated fat. It’s considered a “good” fat. Examples of such fats include olive oil and the fat in tuna fish. The diet changes were not huge. Still, DeBoer hopes that the results mean that teens and their families are getting the message that foods with extra sugar and fat, such as soft drinks and pizza, can be bad for us.

But that message still may not be clear enough, says Melanie Cree-Green. A pediatrician at Children’s Hospital Colorado at the University of Colorado Anschutz Medical Campus in Aurora, Cree-Green was not involved in the research.

“The study needs to encourage us to do more,” she says. The health improvements seen were very gradual, she notes. Plus, the amount of exercise they got stayed the same, or may have even fallen. This could explain why teens ate less food, overall, but still gained weight. (The way activity was measured changed during the study. As a result, it was difficult to tell how exercise habits changed over the 13 years.)

“The big message for our teens,” she says, “is that we need to move more and keep up the great job of cutting out sugar-sweetened beverages.”

The key to success, in Cree-Green’s experience, is for parents to face the challenge of weight loss alongside their kids. When families change their diets together and exercise together, everyone wins.

Power Words

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blood sugar The body circulates glucose, a type of simple sugar, in blood to tissues of the body where it is used as a fuel. The body extracts this simple sugar from breakdown of sugars and starches. However, some diseases, most notably diabetes, can allow an unhealthy concentration of this sugar to build up in blood.

cholesterol A fatty material in animals that forms a part of cell walls. In vertebrate animals, it travels through the blood in little vessels known as lipoproteins. Excessive levels in the blood can signal risks to the blood vessels and heart.

diabetes A disease where the body either makes too little of the hormone insulin (known as type 1 disease) or ignores the presence of too much insulin when it is present (known as type 2 diabetes).

fat A natural oily or greasy substance occurring in animal bodies, especially when deposited as a layer under the skin or around certain organs. Fat’s primary role is as an energy reserve. Fat is also a vital nutrient, though it can be harmful to one’s health if over consumed in excess amounts.

high blood pressure A serious health condition where blood presses too hard against the walls of blood vessels as it flows. This condition can lead to heart disease, heart attack, kidney failure, stroke and other problems.

metabolic syndrome A health condition made up of any of at least three of the following six problems: obesity, high blood pressure, insulin resistance, high levels of bad fats alongside low good cholesterol, extra blood components that cause inflammation and extra blood components that lead to clots. People with metabolic syndrome have an increased risk of developing diabetes or heart disease.

obesity Extreme overweight. Obesity is associated with a wide range of health problems, including type 2 diabetes and high blood pressure.

overweight A medical condition where the body has accumulated too much body fat. People are not considered overweight if they weigh more than is normal for their age and height, but that extra weight comes from bone or muscle.

pediatrics A field of medicine that has to do with children and especially child health. A doctor who works in this field is known as a pediatrician.

triglyceride This substance is the main ingredient of many animal fats and oils. A high level of triglycerides in the blood puts a person at risk for heart disease or stroke.

unsaturated fat A fat molecule made of chains of carbon atoms, where some of those carbon are not fully saturated with hydrogen atoms (attached to as many hydrogens as they can hold). These carbons form double bonds with the carbon atoms next to them. Saturated fats are found in vegetable fats such as palm and corn oil. The double bonds create bends in the molecules, which mean the fats are often liquid at room temperature.