What is the Difference Between Aerobic and Anaerobic Exercises?

Do you know the difference between aerobic
and anaerobic exercises? If not, you might be
doing the wrong exercise for you!

If you're thinking that it's time to begin an exercise program, then you need to be aware of the differences between aerobic and anaerobic exercise. If you don't understand the differences and benefits between the two, you can end up doing the wrong type of exercise for you, which will leave you feeling exhausted and wanting to quit! 

This is what I hear within the low-carb community all the time:

"I'm eating less than 20 carbs a day, lower protein, and lots of fat, so why am I so exhausted?"

There are major differences between going for a leisurely walk and taking a few intense spins around the track. All exercise is not created equal.

Even though most low carbers believe that if you get your heart pumping early in the morning, you'll burn lots of body fat throughout the day, it's simply not true!

That kind of thinking can ruin your weight-loss goals!

There are real benefits for aerobic and anaerobic exercise programs, but to make an informed choice between them, you have to know the effect that each type of exercise has on the body, so you can use each type of exercise to its best advantage.

On Atkins, Exercise is Not Negotiable

On the Atkins diet, exercise is NOT negotiable.

However, when you weigh over 250 pounds, actually making that happen might not be practical, especially if you are new to a low-carb diet and haven't adjusted to the dietary changes yet.

Many dieters wait a few weeks to begin exercising.

This is not a bad idea because you can actually harm yourself if you don't know what you're doing. For example, you can fracture your ankles, due to the pressure of running or jumping on your feet, if you weigh as much as 250 pounds.

However, the misunderstanding of the differences between aerobic and anaerobic exercise can also be quite disabling, so today, I'm going to talk about the difference between aerobic and anaerobic exercise.

I'll also give you real-life examples of aerobic and anaerobic exercises, fill you in on the science, and explain why many people decide to use a combination of the two approaches, instead of just one.

Does Low Carb Turn You Into a Fat-Burning Machine?

I keep hearing a lot of low-carb dieters expressing how tired they are all the time. The typical response they get when asking for dietary help is to "eat more fat."

I know I've said this before, but raising your fat intake might not work if you're tired because usually exhaustion is a result of not understanding the differences between aerobic and anaerobic exercise.

In fact, if you're doing the wrong type of exercise, for your diet, it can make things worse, rather than better. This is because the low carb community regards dietary fat as the holy grail for weight loss, but that isn't how fuel partitioning works.

It is quite common to hear that a low-carb diet turns you into a 100-percent fat-burning machine, but this isn't true.

It isn't true at all.

At any given moment, you use glucose, amino acids, ketones, or fatty acids, depending on the situation, as well as the fuel sources available. And while low carb keeps glucose in short supply and protein in an appropriate amount, the type of activity you choose to engage in won't always burn fatty acids.

Aerobic Definition

Aerobic exercise is actually an energy pathway.

According to the American College of Sports Medicine, aerobic exercise is "any activity that uses large muscle groups, can be maintained continuously, and is rhythmic in nature."

This means that when doing a continuous activity that is repetitive and not so intense that you can't breathe and talk normally, your muscles will extract ATP from amino acids, carbs, and fatty acids, as needed.

This is because oxygen fuels the conversion of energy substrates.

Activity encourages the muscles to take up glucose, amino acids, or fatty acids from the bloodstream to supplement the amount of glycogen that's already stored in the muscles.

Once you've adapted to a low-carb diet, muscular glycogen is relatively low, so muscles are more inclined to use amino acids, ketones, and fatty acids instead of glucose. However, when new to exercise, the muscles might not be proficient in doing that.

This is what Dr. Phinney means when he's always saying that you have to train your body to burn fat.

Anaerobic Definition

In general, anaerobic means without oxygen because exercise is so intense that there is no oxygen that the body can use to fuel that activity.

According to the American College of Sports Medicine, linked to above, anaerobic exercise is defined as, "intense physical activity of very short duration, fueled by the energy sources within the contracting muscles and independent of the use of inhaled oxygen as an energy source."

In other words, the activity is so intense that the muscle must break down its stored glycogen into glucose for immediate use.

This may give you 2 or 3 minutes worth of fuel, as it would be on a very low-carb diet, or it might be up to 2 hours, or less, if your muscle glycogen is full. This is because your muscles use oxygen to fuel the process of burning fat!

You can't use fat to burn fatty acids!

A conditioned heart, can take in more blood and, therefore, more oxygen at the beginning of your sprint or HITT routine, and will be more efficient at consuming oxygen. But once the oxygen is used up, the exercise will convert from being aerobic to anaerobic and you'll last only as long as you have enough glycogen to break down.

If you're fat adapted, and the body is proficient at burning fatty acids, you still need oxygen and glucose to fuel anaerobic activity.

Nutritional Ketosis was developed for endurance athletes. Not for those running sprints or doing heavy lifting.

This is why you don't want to go all-out for long stretches of time. During anaerobic exercise, you need to give your muscles ample time to pull oxygen out of the bloodstream to fuel the next burst.

Intensity and Endurance

The body can only burn fats for fuel during
aerobic exericse. It uses glucose for anaerobic workouts.

Fat needs oxygen to be used effectively, so to rely on fatty acids during exercise, you need to move slowly and smoothly. This allows your muscle cells to be supplied with enough oxygen to utilize fat for fuel.

Something more intense will use more calories, but the oxygen demand will be too great, so the muscles will switch from burning fat to burning glucose because carbs do not require oxygen to burn them.

This is exactly what I was doing when I tried to ride a bike a few years ago.

Up to that point in my life, I had done very little exercise, other than the running around I was required to do at work. During this time, hubby and I went out and bought ourselves a couple of bicycles, and I actually tried to ride that bike.

I thought it would help me improve my balance and enable my eyes to adjust to the vertigo spins faster. But I didn't understand the dynamics of exercise back then, so I wasn't able to get very far with that project.

I didn't have any endurance, and I wasn't able to breathe when riding a bike, so what should have been a nice aerobic workout was actually anaerobic for me.

I was constantly running out of air.

At the time, I just attributed the difficulties to my lack of fitness, which in a way was true, so I picked up a strength-training type of contraption from a yard sale. I have no clue what type of home-machine I actually bought. I thought I was buying a stationary bicycle, because it had pedals, but when I got it home, that's not what it was.

I'm guessing it was a type of elliptical machine, but I honestly don't know what it was. It gave my arms a great workout, though. It had a bar that I pulled towards me, and pedals for my feet to sit on, that allowed my legs to go forward, as the bar for my arms moved toward me.

It didn't work my legs much, unless I adapted what I was doing, by not using my arms to pull the bar towards me.

I was eating at 20 carbs a day, or less, so when I tried to use that contraption, I was seriously running out of fuel. This had nothing to do with the machine. The machine was aerobic, but because I wasn't very fit, it turned out to be an anaerobic exercise for me, too.

The point is that tiredness doesn't mean you are lacking dietary fat.

No matter how much fat I added to my diet, I still couldn't ride that bike or work out on the elliptical machine for more than a couple of minutes at a time.

One alternative would have been to add more carbs.

Moving from Induction into Phase 2, the Ongoing Weight Loss phase, would have given me more fuel for working out. And moving up to my Carbohydrate Tolerance for Weight-Loss would have given me even more energy.

This is why staying at Induction levels on Atkins can be detrimental to your exercise program and make you think that exercise is a waste of time. If you're trying to do some form of exercise that is more intense than a simple walk, you might need a few more carbs, at least until you get more fit.

Most forms of exercise can be aerobic or anaerobic depending upon the intensity with which you do them, so the examples below are just examples. The effort you put into exercise makes a difference in how tired you're going to be afterward.

Average effort, such as the effort you'd expend washing the car or vacuuming the floor, reaps a 50/50 split between carbs and fat. If you put more effort into scrubbing out the bathtub, you can move yourself from an aerobic workout to an anaerobic one fairly quickly, especially if you are not very fit.

Aerobic Exercise Examples

The main difference between aerobic and anaerobic activities is intensity. Aerobic activities are not very intense. They fall into the leisure category, but some forms can be pretty active, depending on your ability to continue breathing normally while doing them.

In this article, we're going to take a look at the various levels of intensity, so you can get a clear idea of why your own exercise program might not be working as well as you thought it would:

Level 1: Sitting

Sitting around and talking is the least intense
activity there is.

The least intense form of exercise, other than staying in bed all day and sleeping, is thought.

Reading and watching T.V. comes in at a close second because you are sitting down. Thought and sitting-type activities, like typing on the computer or talking with friends, uses about 1 to 2 calories per minute to sustain your life.

Most of these calories come from fat because the liver can only hold about 70 grams of glycogen, the storage form of carbohydrates, which equates to 280 calories.

You'll burn through that glycogen in about 2 hours because the body won't allow you to drain more than half of that resource before it turns to alternative sources of fuel.

This is why severe calorie-deficit diets, including very low carb, often tell you not to exercise because you'll burn plenty of fat just sitting around all day.

In fact, at the 1-2 calories per minute rate, basal metabolism tends to be around 1,450 to 2,900 calories per day, just doing not much of anything.

If you're eating fewer calories than you need, you can certainly burn a lot of fat, even with the drop in metabolic rate that so often occurs with huge deficits.

Level 2: Light Housework

Housework burns about double the calories that just sitting would use, so ignoring your housework isn't a good idea. You can really make a difference in your daily energy output by just doing a few extra chores throughout the day.

When I say double, I'm talking about the extra calories you burn from doing housework versus sitting at the computer or on your phone.

When bloggers or the low-carb elite tell you to get up and move, they are not just blowing a lot of hot air. Light housework, or pacing through the house, cooking, laundry, and all of that -- burns 2 to 3 calories per minute while you're doing that.

Once again, the greater majority of that work comes from FAT.

The liver will only convert glycogen, the storage form of carbohydrates, into glucose if your blood sugar drops too low. Otherwise, it saves what little liver glycogen it has for sudden bursts of energy or stress-related experiences.

Level 3: Walking

What do most low carbers recommend for exercise?

Walking.

Walking burns a lot of fat, they say.

Well, that depends on how intense that walk is because walking can range from a very light stroll to almost outright running. And everything in between, of course. My mom used to walk very, very fast when we were growing up. I'd call it race-walking.

It was just that intense.

How many calories you actually burn while walking is very individual. The average person will burn about 50 percent of their walking calories from fat, and 50 percent from glucose, which is still a pretty high percentage overall.

BUT . . .

Where does that other 50 percent of glucose come from on a low-carb diet?

The carbs that you eat, 10- to 45-net carbs, will partially refill your glycogen stores. There are alternative sources of glucose like the lactic acid created during exercise, pyruvate, the glycerol backbone attached to triglycerides, and certain amino acids if the other resources are not available.

This is what many overlook.

Walking doesn't just burn fat. It also takes carbs or alternative sources of glucose to fuel it, and if you aren't eating those carbs, you can get pretty tired. You'll also get tired if you walk too fast for your current fitness level.

So keep that in mind when you're creating a low-carb box for yourself that says carbs are always bad.

Carbs are not bad.

They fuel exercise, especially in the beginning of your low-carb diet when you haven't fully adapted to burning fatty acids for fuel yet. If you shy away from carbs and try to go too low, because you want to lose weight faster, you'll do yourself a very big disservice.

The only exception to this is those who are very insulin resistant. They honestly need to eat fewer carbs, but there is a work around for that: eat extra protein to provide the amino acids you need for gluconeogenesis!

This is why the body has a variety of ways to get the glucose it needs.

Level 4: Aerobics

The next level up in intensity is where those who take exercise seriously tend to gravitate to: what is actually known as Aerobics.

When I was in the weight loss phase back in 2007 and 2008, there were dozens of people riding stationary bicycles as hard as they could and couldn't figure out why their weight loss had stalled.

The thing to remember is this:

The harder it is to breathe while doing whatever you're doing -- whether it walking, housework, or a full blown Aerobic workout -- the less fat you are going to use. And the the less fat you use, the more glucose you're going to need.

While burning carbs is and can be a good thing, because that means you can eat more of them, it's also important to know that this is what you're actually doing.

If you work out above your current fitness level, you're setting up a situation where you need more glucose to fuel that workout.

You burn glucose when you don't take in enough oxygen to burn fat. Most aerobic exercises provide enough oxygen for energy production, but if you do these following exercises more strenuously, you won't have enough oxygen to sustain the activity for very long.

These are typical examples of aerobic exercises. The thing to remember is that you need to be able to breath and talk normally while doing these activities:

• light jogging
• running a marathon
• riding a bike
• swimming
• elliptical machine workout
• walking
• hiking
• dancing
• spinning
• cross-country skiing
• kick boxing
• skating
• bowling

Even if you are fit, you still will only burn about 30 percent of your calories from fat while doing aerobic exercise. Most of what you burn during exercise will still come from glucose. This is because you'll use up the glucose in the bloodstream, which then has to be replaced.

Heavier, and more extensive workouts, can use ketones for fuel, when extra ketones are available. This is why some people doing Nutritional Ketosis prefer to keep their blood ketones at the upper level of optimal.

This is also why you'll see your blood ketones drop after a heavy workout.

The Role of Oxygen in the Bloodstream

Any of the above examples can be anaerobic, depending on the exertion and intensity with which you do them. The difference is always how much oxygen the muscles are able to extract from the bloodstream and utilize.

Deep breathing allows more oxygen to find its way to the muscles.

Low exertion allows you to sustain activity for long periods of time. As you breathe more heavily, extra carbon dioxide is produced and eliminated, so lactic acid isn't produced as it is when you're involved in an anaerobic activity.

You won't get that characteristic burn you get when you overdo it.

During exercise, oxygen comes into the body by way of the breath. That air is filtered by the lungs before passing into the bloodstream. This filtered blood goes straight to the heart, which takes what it needs, and then pumps the blood, nutrients, and remaining oxygen out to the rest of the body.

It is the oxygen that is inside the muscle that allows that muscle to burn fats for fuel. Unlike the liver, the muscles can't use fat to break down glycogen. It utilizes oxygen to do that.

This is why aerobic exercise is done slowly and continuously, so oxygen is in rich supply.

Benefits of Aerobic Exercise

There are many benefits of using aerobic exercise over anaerobic workouts:

1) improves overall health and fitness

2) strengthens your heart and lungs

3) helps to burn body fat

4) improves your mood

5) reduces risk for diabetes

6) improves insulin sensitivity

7) increases endurance

8) can exercise for a longer period

Doing aerobic exercise on a regular basis will help to build your endurance and improve cardiac health, but even low to moderate exertion can move you from the aerobic category into an anaerobic workout.

Level 5: Anaerobic Exercise

Anaerobic exercises do not supply enough oxygen to give the muscles with what they need to continue contracting and relaxing, so the muscles turn to breaking down glycogen to get energy. Breaking down glycogen is what causes lactic acid to build up in the muscles and gives you that after-exercise burn.

That burning sensation has nothing to do with "no pain, no gain." It simply means that you're burning glucose for fuel instead of fat.

Outright running, which uses a lot of oxygen, lowers the amount of fat calories burned from 30 percent to 20 percent. Running takes more carbs to fuel your body than walking does, but also comes with various levels of intensity.

An easy jog isn't the same thing as a flat-out sprint.

Regardless of the fact that you can burn over 10 calories a minute by doing anaerobic exercises, running as fast as you can places a higher glucose demand on the body.

Examples of anaerobic exercise include the following:

• sprinting
• weight lifting
• HIIT Workouts (Interval Training)
• intense jumping

These intense workouts will help to build endurance and can also increase muscle mass, resulting in a higher basal metabolism.

Benefits of Anaerobic Exercise

There are many benefits for participating in anaerobic exercises:

1) better health

2) more stamina

3) increased endurance

4) calories burned more efficiently

5) increase of muscle mass

6) burn more calories at rest, due to increased muscle

7) lowers your heart rate at rest

8) increases red blood cell count to distribute oxygen

9) improves immune system function

10) strengthens bones

11) oxygen uptake during exercise improves

Anaerobic exercises are fairly intense, while you're doing them, so they are almost completely fueled by glucose. This is why HIIT workouts are alternated with slower, more normal bouts of activity.

Of special note for low carbers is that anaerobic exercise helps to keep your glycogen stores very low, so it's easier to maintain an optimal state of ketosis when you're not exercising.

Benefit of Using a Combination of Aerobic and Anaerobic Exercises

When you combine aerobic and anaerobic techniques into your exercise sessions, you'll reap all of the above benefits, rather than just limiting yourself to the benefits that come from each individual type of exercise.

Activities that include both types of exercise:

• tennis
• volley ball
• soccer
• baseball and softball
• football

And other sports that require short bursts of intense effort intermixed with periods of endurance.

In fact, even HIIT workouts can fall into this territory if you alternate short bursts with calm periods of exercise. For more information on doing HIIT, see our article on the benefits of doing HIIT on a low-carb diet.

Does Exercise Increase Metabolism?

Depleting muscle glycogen through carb restriction and exercise has the benefit of increasing the muscles' use and need for fat to fuel your activities later in the day, so there is this misnomer that exercise raises metabolism.

It doesn't.

Exercise helps with energy balance, by burning fat and carb calories while exercising, and it depletes your carbohydrate storage, so that when you're not really doing anything, later on in the day, the body will use more fat for it's basic needs.

This helps to keep you in the optimal state of ketosis and burning body fat as quickly as possible. But exercise itself doesn't use more calories over the ones you burned while doing the exercise.

Any raise in calorie needs is temporary, provided you continue doing the same level of activity as you normally do throughout the day. The best idea is to try and use both aerobic and anaerobic activity to your best advantage.