I am 30 years old, 6'3'' 193 lbs and hoping to end up a lean 200 by early next spring.
Throughout the years I have noticed that if I take my eye of the ball and don't actively surround myself with food and weights I loose weight at a rapid pace. Easily a half pound a week.
Unchecked for a month or two I think I would shrink down to 180lbs before balancing out. Maybe less: I have very small wrists and ankles, and was a gangly runt of a kid until I started working out in college.
Of the two factors, eating and lifting, it is the lifting that seems the most related to maintaining weight.
If I were to maintain my food intake and stop lifting, my weight loss would be greater than if I were to reduce my caloric intake but continued to lift heavy for an hour a week.
Well, this seems somewhat batty to me. Pehaps its simply that working out forstalls muscle atrophy. This atrophy is just more pronounced with me for some reason.
But I have two more exotic theories to explain this violation of the 'calories in/calories burned rule'. The first involved ether and darkmatter, so I won't go there. The second is that perhaps lifting sends a signal to the body indicating that this muscle is not food. This second theory is obviously incomplete, since it doesn't explain where my body is getting the energy instead. But I still think this its a valid question, so I'll restate it.
Its affects on muscle growth and atrophy not withstanding, does lifting somehow protect muscles from being recruited for fuel?
Obviously this mysterious effect would be minor, and generally undetectable in the face of the much larger catabolic issues that arise when training heavy, or operating in a calorie deficit.
Its not a pressing issue right now, since I am back to eating bunches, and have recently started Crossfit, but I thought there might be some science out there around this question.