Kids' meals and combo meals may seem like a good value for those who are budget conscious, but their cost in calories makes them a bad deal all around.

Looking at the meal choices of nearly 500 children and teens eating at five fast food restaurants in New York City, Newark and Jersey City, researchers found that children and teens were more likely to have a sugary beverage if they ordered a combo meal that came with a drink. If the liquid calories from combo meals were removed, it would reduce kids' calorie intakes considerably.

Consuming 179 extra calories just three days a week can lead to an eight-pound weight gain in a year.

Young diners who chose non-sweetened drinks or drank nothing with their meals consumed 179 fewer calories than those who ordered a meal deal that included a sugary drink, like soda, sweetened tea, juice or flavored milk. When customers bought beverages separately, they consumed just 82 calories from soda, a 50 percent reduction.

While only 42 percent of the children and teens bought a combo meal, three-fourths of those meals were kids’ meals which come with a beverage. Half of the beverages purchased were sugary sodas, with juice, flavored milk, regular milk, sweetened tea, lemonade and hot chocolate representing the other purchases.

The opportunity for a “free” soda meant that water accounted for only one percent of beverages chosen when combo meals were ordered. Teens were more likely to choose sugary drinks than younger kids; and boys were more likely to do so than girls.

When children and adolescents consume an extra 179 calories from one fast food meal containing a sugary beverage, they likely exceed the maximum recommended intake of added sugars, which is 120 to 180 calories a day.

Seventeen percent of U.S. children and teens are obese. And, on any given day, one-third of this nation’s 2 to 19-year-olds eat at a fast food restaurant. To put things in perspective, consider the fact that consuming 179 extra calories just three days a week can lead to an eight-pound weight gain in a year.

“Our study strongly suggests that uncoupling sugary drinks from combo meal deals might reduce high-calorie beverage consumption and help to curb childhood obesity rates fueled by these kinds of liquid calories,” said researcher Brian Elbel, of New York University's Langone Medical Center, in a statement.

Several cities around the country have tried to reduce the consumption of supersized soft drinks by increasing taxes on them. Philadelphia leveled such a tax this past summer and one has been in place in Berkeley, California since 2014.

Although this study does not prove bundled fast food meals cause obesity, Elbel hopes policymakers will use such research to guide decisions about effective public health policies that may decrease the consumption of sugary beverages.

The study is published in the American Journal of Public Health.