Obese people often have weak knees because squatting exerts of a force of up to 10 times one's body mass. This computer animation of an obese man makes the problem quite transparent.
Yes they do. As well as the hips, feet, back and so many other parts of the body. I have lost 160 pounds and can't imagine how I ever carried around the extra weight! I understand now why overweight people are so tired! Imagine if you tried to carry around 16-ten pound bags of potatoes every day!!
