The Fat Loss Fallacy

For many years, aerobic training was considered the staple of any exercise program, especially if fat loss was the goal. We were told that if we move at a moderate pace for extended periods of time, we would find ourselves in the “fat burning zone”. We were also told that all this training would help us to live longer, healthier lives because of the cardiovascular benefits. Unfortunately, the idea that slow, steady pace exercise is the golden ticket for fat loss or cardiovascular health is somewhat misleading.

When most people talk about aerobic training, they are usually referring either to running or some sort of group class, but it can really mean any activity that you sustain for long periods of time (technically 3+ minutes, but it can last for hours once it kicks in). Aerobic just means that you are using oxygen to maintain your activity, which differs from those energy systems used to help you sprint, lift weights, or climb a hill on your bike. While running, biking, swimming, etc. at moderate pace for long periods of time can have small benefits, they are inefficient at best. This is especially true for fat loss.

Let's Look at the Research

The problem is that there has never really been any data to back up the fat loss benefits of aerobic training. In a study looking at two groups of obese women, the researchers found that adding 45 minutes of aerobic training 5 days a week for 12 weeks had NO EFFECT over dieting alone. That is 4.5 hours a week of running that did nothing! 

http://www.ncbi.nlm.nih.gov/pubmed/9738131

In a study looking at a six month period where the participants were running for 50 minutes, 5 times per week, the results came out poorly. After over 100 hours of exercise, there was no additional effect on weight or body fat levels. I would not be happy if I put that much time into something that resulting is such little progress. 

http://www.ncbi.nlm.nih.gov/pubmed/17200169

How Did this Happen?

Why were people so sure that this is the way fat loss occurs? 

It all comes back to the misunderstanding of the “fat burning zone”. This zone represents the intensity level at which your body is using fat as its main source of energy. Your body happens to utilize fat more at lower intensities and utilizes carbs more at higher intensities. So it was logically thought that if you are burning a high percentage from fat, then you will be able to burn more fat calories overall! There are two flaws in this argument. First, by this logic, sitting on your couch would actually burn the most fat because you are at rest! The problem is that you are not burning very many calories total, so the percentage doesn’t matter. The second, and more important factor, is that this only takes into account what happens during the workout. There is no recognition of the recovery period after exercise. If you were to only look at what happens in the body during a workout you would notice similar amounts of total fat burned (not % of fat burned) for a given amount of exercise, regardless of intensity. The missing factor in all of this is what happens in the 48 hours after you leave the gym. 

Your body is always looking to restore equilibrium, and the further your push it away from your resting state, the harder it has to work to get back. So when you have a long slow training session, you may burn some calories during the workout, but your body doesn’t have to work very hard to restore itself afterward. The more intense the workout, the more work your body has to do to recover. 

In a study comparing a 20-week endurance training program with a 15-week high intensity interval training program, the researchers found that the endurance group burned over 28000 calories while the interval group only burned around 13500 calories. Despite burning only half the calories, the interval training group actually showed a NINE TIMES greater reduction in subcutaneous fat (this is important because this is the fat that lies under the skin and can give the dimpled cellulite look). 

http://www.ncbi.nlm.nih.gov/pubmed/8028502

The Fat Burning PLAN

The truth is, exercise is not about what happens at the gym, but it is what your body does in response to that exercise during the recovery period. This is why high intensity training like weight lifting and intervals work the best; they force your body to recover. This doesn’t mean you need to go to the gym and kill yourself right away, just start building up your intensity over time. If you can only workout 2-3 times per week, weight training is always better due to the large requirements it places on your muscles. Interval training is a good supplement to weight training but should not replace it.

One final note: long, slow activity can be great for recovery. While it does not do much on its own, staying active can make a big difference in how well you respond to your more intense exercise. If you weight train and then sit for the next 48 hours, your body will not recover nearly as well (aka not burn as much fat) than if you stayed active. Walking, stretching, foam rolling, hiking, gardening, light swimming and biking; these are all good activities for helping you to recover from your more intense bouts of exercise and should be done daily if possible.

So there you have it. Strength training, plus interval training, plus daily movement is the way to go for burning fat. If this is your goal, maybe it’s time to evaluate your current exercise program and see if what you do aligns with what you want to achieve.