I don't know what his routine actually is, but I used to look similarly to what he does in that picture. I looked that way while also likely achieving that calorie intake. I was at the time Sport Climbing spending nearly 6 hours a day in a climbing gym , and doing nothing else in terms of weights or what have you. All the lifting and resistance was based purely off of my own body weight so I never really built mass, it just seemed like I built muscle on top of muscle. At my personal physical peak I could do one arm pull ups with just my middle finger through a sling to support my body.
He's pretty lean I wouldn't be surprised if he was doing some type of exercise that focused purely on an established body weight and revolving around that. Take a look at images of sport climbers, they all look like him and they pound back calories.