Personally I don't see how any of the things they are doing wouldn't be possible if the kid was overweight. I've known plenty of overweight people growing up and they generally had no problems doing the same activities. Sure, they may not be able to run as fast or jump as high or have as much stamina but I can't see that as making them a liability and besides denying an overweight person exercise just compounds the problem does it not?
http://www.cnn.com/2013/07/19/health/boy-scouts-bmi/index.html?hpt=hp_t3
http://www.cnn.com/2013/07/19/health/boy-scouts-bmi/index.html?hpt=hp_t3