They must go through many years of training before they become famous. Students practice dancing and singing for 8- 12 hours every day. If you can stick to it, your body shape will not be too bad.
Then most Han Xing like gyms, where they can strengthen muscles, such as waist, legs, arms and so on. General exercise in the gym 1-3 hours.
Then there is the diet. The food should be as light as possible and the salt content should not be too high.
Korean stars, from the perspective of singing and dancing, are worthy of respect.