Aerobic training or strength training: which one is better for fat loss?
The pros and cons of aerobic training
To lose fat, I need to do more aerobic training; weight training will just bulk me up, and I don't want that; I need to lose 10 pounds before I come to see you, then we could lift weights to tone up.
I hear these comments often. As a trainer, it is very frustrating to convince people otherwise. There are many myths and misunderstandings about aerobic training and strength training that makes it very difficult for one to reach his or her goals of losing fat and reshaping the body. I will explain below some of the good...and some of the bad about aerobic training, and then compare it to strength training.
- Aerobic training burns calories from fat. This is true, and the main reason why exercise physiologists and most personal trainers recommend aerobic training. When you are under the anaerobic threshold (the point where you cannot continue exercise for long), energy comes from the fat stores, along with glycogen and oxygen to create ATP (Adenosine Triphosphate), which is the fuel for muscular contractions. It is a lengthy process that takes time for the conversion (and a reason why you cannot burn fat with strength training). Energy use works on a continuum; the easier the activity, the more the energy is from fat. Conversely, the harder the activity, the more the energy is used from glycogen stored in the muscles. In other words, you actually burn more calories from fat sitting on the couch watching T.V. then you do from even a moderate pace jog. If so, why do couch potatoes typically have high body fat levels? I'll explain in more detail later.
- Aerobic training is good for working the heart and lung muscles. It certainly improves the conditioning of these systems.
- If you want to run a marathon, you must go out and run. This is sport specific training.
- You don't burn as many calories as you think. A typical aerobic workout burns about 200 to 300 calories. That is not much, and can easily be replaced by eating a candy bar or 2 alcoholic drinks.
- Your body attenuates to it. In short, it gets more efficient with the exercise. If, at first, it takes your body 300 calories to do a moderate bike ride for a half an hour, after a couple of weeks of bike riding at the same intensity, the body will only burn 250 calories to do the same activity. This makes it harder to see continued fat loss over time.
- Too much aerobic activity does not allow for recovery. When you start hitting fat loss plateaus, most trainers and exercise physiologists recommend doing more time and adding more days to see gains. This leads to over training. The body starts to wear down, leading to joint and connective tissue injuries. Over the long term, this leads to a decrease in the functionality of the body.
- Loss of muscle mass. If you don't use it, you lose it. Low to moderate intensity exercise does not promote muscle maintenance. Muscle is important because it increases your metabolic rate (burning more calories even when not exercising), and muscle is also important for joint stability and better mobility.
How does strength training compare? First of all, strength training operates in the anaerobic energy systems, which means it gets the energy needed for ATP production from the glycogen stores in the liver and muscles. It does not get energy from the fat stores. Once again, that is why aerobic training is recommended for fat loss instead of strength training. However, one does still burn calories from strength training, typically about 200 to 300 calories a workout. Another benefit of strength training is the extra calories burned by more muscle. Some estimates range from about 7 to 10 calories a day per pound of muscle up to 30 to 40 calories a day per pound of muscle. I tend to believe it is closer to the 7 calorie range. These calories are used even when not exercising, thus increasing your basal metabolic rate (calories burned by the body without exercise). Another benefit that strength training has is the EPOC (excess post-exercise consumption), also known as the "afterburn". This simply means how many more calories are burned above the resting metabolic rate for the body to recover after an exercise bout. Research finds that the higher the intensity of an exercise, the longer the EPOC. Over time, this is an important calorie expenditure piece. So how does this help with fat loss? Even though calories burned by strength training are from glycogen and not fat, the body will draw on the fat stores during rest and recovery. Another benefit of strength training is that you do not need to increase frequency or duration to see continued gains, just the intensity over time.
It is important to remember that total calorie intake is very important for fat loss. My general recommendations for clients are as follows: 1500 to 1700 calories a day for women; 2000 to 2300 calories a day for men if they want to see fat loss. By combining a good strength training program with a sound nutrition program, great results can be achieved with as little as 90 minutes of exercise a week. For those of you who don't have much time (or who don't want to commit to many hours a week of exercise), strength training is the way to go.