It's a terrible way for people in the overweight or obese range to lose weight. Their primary issue comes from what they eat. And just making themselves more hungry and exhausted isn't going to help that. Similar thing with putting a hundred or more pounds of fat onto already straining joints. Especially since most of them already have issues properly guessing caloric intake.  Then on top of that, most resources dramatically overestimate caloric burn for various exercises. Even something one would think of as pretty accurate like fitbit or the like is still usually more a guestimate at best.  Gyms can be a good place for skinnyfats in the healthy BMI range to drop excess pounds. They usually need tweak their diets. But for the most part they're usually doing things more or less right. But it's just a waste of time for overweight and obese people. I mean I've been jogging for years. And in that time I've seen fat joggers jump in. Time, and time, and time again. I've never once seen any of them stick it out. Despite the fact that they'll often get a tremendous amount of encouragement.  Obesity isn't an issue of not working out. It's an issue of eating too much of the wrong thing. Time spent in the gym would be put to far better use by investigating healthy food they could make and enjoy long term.