Pick a recent day that represents how you typically eat. Try to remember everything you consumed and run it all through a calorie calculator, like the one at . If you’re like me, you’ll see a problem. I estimated that I ate about 2,000 calories a day, but it was really more like 1,700—nowhere near what I needed to maintain my existing muscle mass, let alone add to it. “Underweight people tend to overestimate their daily calorie intake,” Aragon says. “Then they incorrectly attribute their low weight to a high metabolism.”
If you try to train up to 6 hours total, 4 or 5 days per week, you will risk overtraining and make your body prone to injuries. That amount of exercise will make you feel mentally and physically drained, especially if you’re underweight. Understand the signals that your body is sending – if it’s sore, then it needs some time to recover. There is no building muscle without proper post-workout recovery, so don’t think that you will enhance your results by living in the gym. However, you’ll come back stronger once you provide your body the time it needs to recover.