Some kids can taste as little as 0.005 teaspoons of sugar in a fluid ounce of water. Others need three teaspoons until they register it. Logic would suggest that the less sugar-sensitive—those who need to add more sugar to get the hit of sweetness—would be more likely to be obese, right? Not according to new research.
A new study released by the Monell Center, which specializes studying taste and smell, found that it was the kids who could taste sugar at lower concentrations who were more likely to be overweight. Those kids also often had a specific gene variant that is known to influence receptiveness to bitter tastes.
The researchers looked at 216 healthy children between the ages of 7 and 14. Each one was tested for his or her sensitivity to sucrose by being given solutions of water and sucrose to swish around their mouths and then being asked if they could taste anything. Various aspects of the children’s weight were also recorded and their DNA was tested to find commonalities between the more sensitive subjects.
“We went into the study thinking that the kids who were very insensitive to sugar were going to be the obese kids, because they needed to consume more for the same effect,” says Danielle Reed, PhD, a behavioral geneticist, the lead author of the study which will be published in the journal Nursing Research. “But we actually found the opposite. The obese kids were more sensitive.”
The researchers can’t quite figure out why, but speculate that it might be because if sugar has a very strong effect on the receptors on the tongue, it may also have a strong effect on other organs in the body. It could also be that sugar has a different effect on the biology or metabolism of those who react to it in smaller doses.
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In general, children are more sensitive to sugar than adults and, as the junior mob riots in Dylan’s Candy Bar prove daily, they like higher levels of sugar than adults do and will make heroic efforts to seek it out. These preferences decline during adolescence, as kids stop growing. Scientists think that’s because sugar is great for bone growth but used to be hard to find, so humans evolved to favor it while young.
While parents tend to protest if their kids are adding a lot of sugar to their food, Reed says the children may not be doing it just to be excessive. “The big message is that kids are really, really different in their sensitivity to sugar,” says Reed. “Parents may be freaking out that their kids are adding a lot of sugar or want a lot of sugar in things, but certain kids are pretty insensitive so it could be that they’re adding it just so they can taste it.”
At this stage it’s not worth getting your child’s DNA analyzed to see whether they’re more or less sensitive to sugar, or if adding a lot of sugar is going to make them fat. There’s a much easier way to find out: look at your kids’ parents. (Often, that’s you.) If you have a chubby elementary or middle schooler and aren’t sure if he or she is going to grow out of it or needs to change his or her diet, your go-to data set is the chubbiness of you and your spouse.
While there are many myths around how unhealthy sugar is—no it isn’t making your kid hyperactive—it’s still pretty clear that it should not be a big part of your or your child’s diet, and this study doesn’t change that conventional wisdom. “When we were evolving sugar was very rare and very helpful,” says Reed. “Now it’s too available and it has turned on us.”