Thank you for your coherent comment.

There are also very small percentage of people that become obese due to certain illnesses, which makes it very difficult for them to lose weight unless they work out extremely hard and dramatically change their diet. So we cannot really be ever sure, that someone is obese, because of their lack of physical workout.

When it comes to heavyweight sports people, they are sometimes both muscular and obese. Maybe the extra weight coming from fat tissue helps them to get better momentum when lifting weight, I don't know. All I have learnt is that those obese heavyweight lifters can still have serious health problems due to obesity. They are certainly healthier than obese people who do not do any physical activity but they are unlikely to be healthier than other heavyweight lifters who aren't obese.

Regarding bodybuilding. Going to extremes with body building is not healthy neither.
Developing extensive muscle bulkiness is not sustainable. Overdeveloping of one body system puts stress on other body systems like skeletal system, cardiovascular system, digestive system (for example, through saturation with forced high protein diet) and so on. From scientific perspective extensive bodybuilding is an unsustainable physical workout. It is an activity which has it's oots in the value system of our culture. It is unsustainable, just like many other physical activities within our culture (fighting sport is one of the examples - smashing each other's faces and brains for competition and entertainment of others).
Just because something is popular and considered normal within society, does not necessarily make it sustainable, logical and scientific.
From evolutionary point of view (foraging, then hunting and foraging), our bodies have evolved to function better if we have leaner and more athletic body rather than muscle-bulky. This sustainable and healthy body frame/state is being shaped by anaerobic and aerobic physical physical workout, not by bodybuilding workout.
Hominae (including us) have evolved through millions of years by performing a lot of anaerobic and aerobic not by wasting energy and time on pointless heavy lifting (unless occasionally forced to carry something). Bodybuilding is an invention of 20th century. It had never been popular before, with few exceptions like some wrestling in Ancient Greece, although even at that time it wasn't to such extent. Also Ancient Greek olympics were more about admiration of human body (athletes performed naked), rather than competition. Overdevelopment of muscle system requires a lot of nutrition and energy food resource, so this activity wasn't possible at the times of resource scarcity. Now it is possible since we eradicated food scarcity in Western countries, hence this "sport" became so popular in the West. In Asia and Africa this activity is still not very popular. Specifically in Asia, their cultures have been focused more on internal development (yoga, internal martial arts, tai-chi, etc).