The major catabolic effects of long distance running link closely with the release of the hormone cortisol, as explained below:

A cortisol excess can lead to a progressive loss of protein, muscle weakness and atrophy, and loss of bone mass through increased calcium excretion and less calcium absorption. That is one of the reasons long-distance runners tend to have skinny physiques. (1) With the amount of stress that runners place on their bodies, they have high levels of free radicals as well as cortisol. Excess cortisol can also adversely affect tendon health. Cortisol causes a redistribution of bodyfat to occur through an unknown mechanism. Basically, the extremities lose fat and muscle while the trunk and face become fatter. Some of the signs of overtraining include higher cortisol levels, which may cause depression-type effects.

 If you want a lean – and more importantly fit and healthy – physique, don’t focus all of your efforts on running. Sure, you’ll get lean doing that, but it won’t be a look you desire unless looking like you just escaped a concentration camp is desirable to you.

Focus on weight training first, this goes for both men and women, and have your cardio sessions modeled after a typical hockey shift – full out sprints for 30-45 seconds, then 2-3 minutes at a reduced pace or complete rest. Rinse and repeat. Start with 10 minute sessions and slowly ramp up in the weeks to follow. The odd jog is fine if you insist, but keep it short to minimize catabolism.

Lean body mass is difficult enough to gain and maintain, don’t make it harder on yourself. Less is more sometimes. Seriously.