Well i think it does affect because you have to carry more weight
NO! It affects your endurance . I have a friend who is overweight. And I also have a friend that is the most athletic person who I've ever seen. So the weights are about 170lbs. and 97-99lbs. The first friend has never played a sport in her life, and the other plays soccer, softball, and swim team. There is this City Cup game we do every year to raise money for people in need. One of the races is the 15 meter dash. My friend who is over weight competed for fun. And she beat every single slim, fit, healthy, athletic girl who competed by about 4 whole seconds. When my friend and I have ran together, she takes off and gets about a half a mile ahead of me, but she doesn't have endurance. She is a faster runner, but she doesn't have the cardiovascular endurance to stay running that fast, that long. I soon catch up to her. She has to stop and rest. After that, she can take off again, but can't do it for very long. So really your weight doesn't effect your speed, it effects how long you can go running.
Whoever wrote this has no idea what they are talking about. Endurance is all about how you train. Your speed is probably a little bit slower when you are heavier though.