For some reason people seem to have the idea that running will create fat loss. There’s two ideas that probably contribute to this: the best runners are usually very lean, and the 1980s obsession with aerobics. The latter especially created a tradition so that “everybody knows” you go run or do aerobics classes to get in shape. Right?

As usual, it’s not that easy. There is some truth to the fact that steady-state aerobic exercise does tend to preferentially use circulating triglycerides as a fuel source (body fat, effectively). However as the current fad towards interval training will quickly remind us, the fuel source isn’t the entire story. There’s something to be said for shorter, more intense exercise. I won’t go into the details because they aren’t terribly important here, but maximal activation of anaerobic metabolism tends to chew up more calories and do favorable things for nutrient partitioning: calories go to muscle instead of fat storage, and more fat ends up being burned over a 24-hour period.

OK, so we see that brief, hard exercise carries some benefits. Aerobic exercise simply isn’t a “strong” stimulus to your body in the same sense. It’ll waste calories alright, but the overall magnitude tends to be lower; you have to do more total work to see the same effects. This is where the long-distance running starts to catch up to you. Further, there are some systemic issues we have to worry about that transcend the micro-level slices of biochemistry.

Consider stress on your body. Stress from work, stress from lack of sleep, stress from exercise, all of these things are additive. Fatigue builds up over time, and if you’re not recovering properly it will gradually wear you down. You can think of your ability to handle stress as being a sink full of water – there’s only so much to go around. Every stress in your life drains the sink a little, and some take more than others. The faucet can only put so much water back in, even when you open it all the way, so you can only recharge so much in a given time frame. If the water is flowing out of the sink faster than the faucet can put it back, eventually the sink is going to empty out. Following me so far?

OK, so when you go into any “hard” training routine, you’re pulling the plug on the sink. Water is gushing out. You can tolerate this for awhile – depending on the person and the circumstances, you might make it a few weeks to a few months. But sooner or later the sink is going to empty out.

When I say “hard” training, realize that this applies to anything – strength sports like powerlifting and Olympic weightlifting, bodybuilding, sprinting, martial arts, and yes, even long-distance endurance sports like marathons, half-marathons, and triathlons. When you train for a sport, your goal is to improve performance at that sport. This, by definition, implies that you’ll have to drain the sink a little; you’re using that “adaptive energy” (the water) to create changes in your body. That’s a part of the process.

Here’s where people trip up, though: they assume that the running is just calorie-wasting. Well, it is – but it’s also a powerful stress on the body. Now compound this with a diet. When you’re training for a sport, nutrition is there to help keep the sink full. When you go on a diet, you turn the faucet off. The sink might have been balanced, or at least draining very slowly, before. When you diet, the sink is just emptying out.

Remember one thing: getting in shape is a different matter from staying in shape. The former requires hard training and recovery – to include nutritional support – and is not really compatible with dieting. The latter is just a matter of paying attention to diet; you’re already in shape, and thus don’t have to use up any water (recovery ability) to stay there. Someone that wants to get in shape is going to have to tap into that reserve.

Obviously getting in shape for a sport, even if it’s something that sounds harmless like a half-marathon, is just not compatible with dieting to drop fat. And yes, I’m writing this specifically to target the group of people that want to get in shape while training to run in a marathon. It’s an admirable goal, but realize that it is not compatible with weight loss.

Ideally you’d want to include some conditioning work in your training; what I’m saying here is not to go overboard with it. You can’t just say “aerobic cardio doesn’t work”; obviously it does, as bodybuilders have used it to get lean for decades. It may not be the best approach from the standpoint of muscle retention, but it does work.

The more fat you hold, the easier it’s going to be to drop fat with just about any exercise. As you get leaner and want to continue getting leaner, you’ll probably want to change the strategy. Yeah, you can chain yourself to the treadmill, but that carries its own problems – bodybuilders that do this can end up losing a lot of muscle mass, and for women especially the post-contest rebound can be a bit unsightly.

My preferred method would be to incorporate both anaerobic methods (such as intervals and tempo runs) along with limited amounts of aerobic exercise. The utility of aerobic exercise is that you can do it literally every day, as long as you’re not going crazy with the distance or time. Doing a light session for 30-60 minutes is hardly going to kill you, but it can definitely make a difference over time; some women may in fact need that kind of regular activity to see body fat drop (especially stubborn lower-body fat). The anaerobic work is more effective per unit of time, but it has the drawback of being one more stress on the body, and if you’re doing any strength-training for your legs, then you can have some issues while on a diet.

There’s also something to be said for frequent rest weeks. You might be able to keep up 2-3 strength sessions, 2-3 interval sessions, and 5-6 aerobic sessions for 2-3 weeks, but if you’re in a calorie deficit, you’d be well advised to throttle back every 2-4 weeks. Basically just cut your workload in half, or even to 1/3rd so that your body can recover. Three weight workouts becomes one, maybe cut the intervals out entirely, and only do 2-3 aerobic sessions. This gives your body a break, which is very important while you have limited recovery. Inflammation heals, hormones reset, water is lost and so on.

It’d be nice if it were as easy as just going out and running until you were lean; some people might be able to do this, if they have the genes for it. Most people won’t. They’ll run into issues with the body fighting back as their “recovery sink” empties out. Fat loss stops, and instead of doing the one thing that would help – resting and eating more – the average person assumes s/he isn’t working hard enough and eats less food while doing more activity. Sooner or later these people give up in frustration.

The trick is to help your body keep the sink as full as it can. Work with the adaptation process, not against it. You’ll be much happier (and leaner) for your efforts.

Come discuss this article on the forum.