I always feel that this excuse is one always thrown out when they really don't want to make any effort because losing weight is 90% diet anyway.  If they did any research at ALL on weight loss (other than the Facebook friends selling smoothies and wraps) they'd learn that they don't need to work out 4 hours a day to lose weight, they just need to eat less, and preferably eat healthy foods.  Exercise makes you fit and burns some calories.  Eating less will make you lose weight much faster than introducing exercise.  Also, when a person is really fat it's hard on the body to do vigorous exercise, but they can go for a walk a few times a day in literally any outfit.  Fitting into cute active wear should be a reward for losing weight, not a requirement.