in the beginning of the article, it says that the data is based on what the teens "reported". not saying it automatically discredits the study but i always have a hard time with studies where the participants have to report stuff on their own. first of all, some of the participants could be straight up lying. say the researchers gather a group of teens and ask them to participate in this study where they have to exercise frequently and eat a specific amount of calories and they can't go over. they ask fukking teens to do that and pay them. you better believe some of them will say they did their workout even if they didn't.
also, besides the lying, it's even possible that they make honest mistakes when counting their calories, or maybe even mistakes on exercises. not everyone is super educated on working out and if they're asked to get their heart rate to a certain BPM for 20 minutes or whatever, who's really checking that she's doing it right? so even with good faith, there could still be some biased.
i'd really like to see how they conducted that study. and to be fair, i understand that it would be very difficult to get 100 teens of each races, secluded in a lab, getting them to eat the exact same food and doing the exact exercises at the exact same heart rate for months and then record the results.