"Lower intensity aerobic training is relatively useless for optimal fat loss purposes.

 Furthermore, for some populations, it's likely to be detrimental."— Alwyn Cosgrove

My theory (based purely on the observations of my clients' progress) is as follows:

Aerobic training encourages the body to adapt by becoming "energy efficient". This means it will take less fuel to perform the same amount of work. Although an energy efficient body sounds great, it isn't — not if you're trying to lose fat. Energy efficiency just makes the job of losing fat more difficult.

To simplify it as much as possible, fat loss comes down to creating a caloric deficit. The body burns calories primarily by muscular work. Steady state low intensity aerobic training does not require much work from the muscular system and does little or nothing to even maintain muscle tissue.

So, if muscle is "fat burning machinery," then aerobic training makes that machinery smaller and more fuel efficient, which is not what I'm looking for.

So we have an activity that burns calories, but the more you do it, the fewer calories it burns with each subsequent exposure (so to burn the same amount of calories you have to go harder or longer), and in all reality it just doesn't burn that many calories anyway.

Aerobics never helped this fat bastard.

A decent pace for a 180-200lb individual would burn about 10 calories per minute. Thirty minute aerobic sessions will burn around 300 calories. Performed three times per week, with no reduction in work performed (i.e. you keep increasing intensity or time as you adapt), you're still looking at about a pound per month.

If you woke up an hour earlier each day and just sat and watched TV, you'd burn about the same (7 days x 60 mins x 2 cals per minute).

Now granted, there are exceptions. Complete beginners, obviously, and precontest bodybuilders (or those wanting to go "beyond lean"), but for most people it's an extremely inefficient fat loss modality.

Anecdotally, you only need to stand at the finish line of a marathon and look at the physiques of the masses. These people developed the joint integrity and muscular and cardiovascular endurance to run 26.2 miles — some of them running in the 3-4 hour range — yet they haven't created enough of a metabolic demand to create significant fat loss.

Effective fat loss hinges on burning as many calories as possible during the workout, and elevating metabolism so that we burn more calories per minute, all day long. Aerobic training fails on both counts.

So why has aerobic training become so popular?

In the past, fitness professionals and researchers have looked at how much fat is burned during the exercise session itself. This is extremely short-sighted.

As my colleague Alan Aragon said:

"Caring how much fat is burned during training makes as much sense as caring how much muscle is built during training."

Think about that. If we looked at a weight training session that started at 9AM and finished at 10AM, how much muscle would we see built if we stopped looking at 10AM? None.

In fact, we'd see muscle damage. We could make the conclusion that weight training does not increase muscle; in fact it decreases muscle, right? It's only when we look at the big picture — and look at the recovery from the session — that we find the reverse is true: weight training builds muscle.

Fat loss training is the same way. Someone talking about the benefits of the "fat burning zones" or "fasted cardio" is a sure sign that the individual has stopped looking at the end of the exercise session. They have come to the conclusion that fasted, lower intensity steady state exercise burns the most fat and made a massive leap of faith to suggest it is best for real world fat loss.

Using that same logic these same people would suggest you avoid weight training if you want to grow muscle.

— AC