The common belief is lifting heavy weights will make you big and bulky. But the notion is not supported by science, according to a New York Times article. Producing bulky muscles requires not just heavy weights but heavy calorie consumption as well, typically far above the 2,000 daily calories recommended for many adults.
For people who lift weights to tone up and slim down, experts say, a regimen that includes a combination of challenging weights and fewer repetitions can help significantly. In a 2002 study, for example, scientists looked at what happened when women performed various resistance exercises at different weights and repetitions (85 percent of their maximum ability for 8 reps, versus 45 percent for 15). Subjects lifting more weight fewer times burned more energy and had a greater metabolic boost after exercise.
[Source]
Chapter: Health :: 12 July 2010