James Stephen Donaldson, the world's most-subscribed YouTuber popularly known as 'MrBeast', took to Twitter on Thursday to reveal that he has lost weight. The 25-year-old tweeted, "Woke up and realised I was obese so I started lifting and walking 12,500 steps a day." He added, "Still got a long way to being yoked...but I'm happy with my progress so far."