"You can't have beer, hash browns, burgers, or anything fried. No carbs," he said. "And you have to work out five times a week."
"I'd check in maybe once a week and I'd say, 'They cast it yet?' and I would just keep working out," he says to The Mirror.
"Finally, I got in good enough shape that I took a picture of myself and sent it to my agent."
"If you cut the crap out of your diet and spend an hour a day doing something physical, you'll feel better mentally, physically and spiritually, because it's all tied together."
"Honestly, there's no trick or secret to it. It's about getting after it and being patient and consistent.
"And it's not about starving yourself, because you want to give your body proper nutrition.
"And think about who you want to be in six months or eight months or two years' time, whatever it is."
Pratt told Men's Health he initially lost 15kg in six weeks by running "five or six miles a day, eating leafy green salads and protein shakes and cutting out all alcohol".
Chris Pratt's Back, Biceps and Abs workout
Warm up: Stretching & 10 mins jog on the treadmill
1. Pull Up — 5 (sets) — 15, 12, 10, 10, 8 (Reps)
2. Pull Downs — 5 — 15, 12, 10, 10, 8
3. Hammer Strength Row — 4- 12, 12, 10, 10
4. Heavy Dumbbell Row — 4 — 12, 10, 8, 8
5. Barbell Curl — 4 — 10, 8, 8, 6
6a. Hammer Curl — 3 — 12
6b. Reverse Curl — 3- 127. Plank — 3 — 20 secs
8. Hanging Leg Raise — 3 — 15
9. Sit Up — 3 — 20