Recent studies published by the Research Quarterly for Exercise and Sport, has shown that contact sports can actually cause your body to convert cells into lean tissue. The demands of high-impact sports, like boxing causes the brain to send signals to the body that it needs to be protected by muscle instead of by fat. As a result, this conversion occurs at a cellular level.
This, in theory, isn’t all that different from bodybuilding or muscle strengthening in general. By placing a high demand of weight or volume load on your muscles, they harden, grow and become stronger. The breaking-down or tearing of muscle tissue, forces the muscles to rebuild stronger and bigger.
This finding has very specific applications to boxing because it is about as high contact and high impact as you get in sports. The message here is that your body will adapt and conform to do as much as you ask it to do. Part of your job as a combatant is to create a suit of armor you can take into battle; one that will not only inflict damage, but will also help protect you.