Doubling calorie needs is hard if you have a sedentary job in the modern world. Walk / Cycle to work every day at a fast pace (1 hour total). Play some kind of

Doubling calorie needs is hard if you have a sedentary job in the modern world. Walk / Cycle to work every day at a fast pace (1 hour total). Play some kind of sport daily at lunchtime / after work (1 hour). You’ve just used an extra 1000 calories or so. Congratulations: you’re almost half way to your goal of doubling your daily calorie output. Plus you still need to spend time doing all the other stuff to keep your life going outside work. It can be done, but modern life guides people to a constant sedentary lifestyle. Drive to work, sit at home in the evenings watching TV etc etc.