Exercise & Weight Loss

Be forewarned: This is going to be a long one.

I DON’T REALLY NEED TO LOSE WEIGHT. If anything, I wouldn’t mind gaining back a pound or four (as long as it’s all mitochondria-rich type 1 muscle fiber).

However, I have a friend at work, a guy I’ve worked with for a long time, who, a few years ago, needed to lose a lot of weight. Furthermore, I had an audience that was fairly interested in the subject as well. So for years on end, I read, researched, evaluated and shared what I learned about weight loss. But, at least for my friend, it never quite did the trick … until this one day.

He was so fed up he’d grown desperate. At the same time, I was pretty sure I’d figured it out. So I barged into his cubicle and sat him down and said, “Look, I think I have an answer for you, but you’re going to need to stick to this—exactly this—for a long time. You can’t bail on it after four weeks, because it’s going to take longer than that. You’ll need to keep it up for months on end.”

Then I explained to him what I’m about to explain to you.

And over the next year, he proceeded to lose over 100 pounds.

He’s gained a few pounds back, but for the most part, he’s kept it off.

So that was my preamble. Are you ready to hear what I told him? It’s not going to be pretty, and it’s not going to agree with everything you read on the internet. I don’t have a PhD or a fitness certification. My science might be a little bit messy, but that doesn’t mean it’s wrong.

Here goes …

Different types of exercise use different energy systems. And there’s really only one energy system that directly burns fat. It’s not the system you use when you do a clean and jerk, and it’s not the system you use when you do pull-ups, sorry to say. It’s also not the system you use when you do a 100-meter dash. Take a hard look at this chart:

Table showing that aerobic metabolism is the only fat-burning energy system in your body.
I totally swiped this chart from Alan Couzens. Alan, if you don’t want me to use it, please just say so, and I’ll remove it.

Got a good look? Look across the top of the chart. Those are the continuous durations of particular exercises. An example of an exercise that takes 6 seconds or less might be bench press or squats done with 80–90% of maximal load. Another example might be full-out sprinting as fast as you possibly can. On the far right, an example of an exercise that lasts eight hours might include an Ironman Triathlon, long-distance cycling events such as the 206-mile LOTOJA, or swimming from Florida to Cuba … yes, seriously.

Now look down the left side. Those are all energy systems. Underneath every “duration” is the percentage of each energy system being used. Bench press to exhaustion, for example, uses ATP, the most basic unit of energy in your muscles, for 44% of its energy. “CRP,” which refers to creatine phosphate, keeps restocking your muscles with ATP as you use it up, and is responsible for 50%. Then “anaerobic glycolytic” — aka, carb-burning anaerobic exercise — gives 6%.

Now look at the bottom left. Notice that word “lipolytic” in the light-blue box? That word means “fat-burning.” Notice what percentage of your lipolytic system is being used for your 6-second max-out bench press. Yep, zero. Now look at what percentage of your lipolytic system you’re using to do your 8-hour Ironman Triathlon (which, by the way, makes you fast enough to be a pro — go you!). Yep, 71%.

Okay, I just stuck this in here because I didn't want you to get bored with the nonstop text. Keep reading.
Okay, I just stuck this in here because I didn’t want you to get bored with the nonstop text. Keep reading.

That’s not something science needs to prove; it’s an axiomatic truth in exercise physiology. Lifting weights and sprinting don’t use fat. You don’t even TOUCH fat unless you do an exercise that lasts for 30 minutes nonstop. Ever tried bench pressing for 30 minutes? (Okay, maybe you have.)

That’s not to say weightlifting and sprinting don’t have their place — they do. And studies have shown that they burn more calories than the experts used to give them credit for. And sure, I’ll concede that weightlifting can even enhance your weight loss. But weightlifting and sprinting don’t directly burn fat.

What does? Well, look at the chart. It’s aerobic exercise that lasts for 30 minutes or longer. In fact, if you want to burn a decent amount of fat, you should be aiming for 60 minutes, not just 30. (Although there is a study that shows beginners lose more when they start with 30-minute aerobic sessions. So that’s a good place to start. But eventually, it will take more than that.) If you can, you’ll metabolize more fat doing a workout that last 90 minutes.

When you do consistent aerobic workouts over time, your body makes important adaptations, even before you see a change on the scale — and those adaptations will eventually lead to the right kind of weight loss. Your heart grows larger and pumps more blood. Your blood volume increases. You actually get more mitochondria in your cells. Remember those guys — mitochondria? They’re the little power plants your body needs to process energy at the cellular level.

And when all of that stuff happens … (drumroll please) … you get better at burning fat!

You’ve probably seen this. You’ve seen the skinny marathon runner or triathlete in your neighborhood. My brother recently took up training for and running half marathons, and he’s lost probably 50 pounds with that regimen. I promise I’m not making this stuff up.

You’ve also probably seen some people who look like they’re doing the right things but aren’t losing the weight. Perhaps they’re counteracting aerobic exercise with a poor diet — having sugary snack before every workout (which will predispose your body to using carbs during the workout), or guzzling HFCS-laden “sports” drinks as they slog through a session on the treadmill. Or, just maybe, they’re doing all of their workouts at too high of an intensity …

… on to the next chart:

Once again, I totally swiped this from Alan Couzens (find him at http://alancouzens.com).
Once again, I totally swiped this from Alan Couzens (find him at http://alancouzens.com).

Part of why long so-called “cardio” works to burn fat is the fact that you simply can’t do a 90-minute workout at the same intensity at which you can do a 90-second workout. As you can see from chart #2 here, the higher the intensity, the greater the proportion of carbohydrate to fat — until you simply aren’t using fat at all. The trouble on the other end, though, is that your total calorie burn (i.e. energy expenditure) is lower when you’re burning a higher proportion of fat. (In this example, the fat burn is even greater than it would be for you and me, because this chart shows the fat usage of a highly tuned endurance athlete.) So if you exercise at too low of an intensity, it won’t be worth your time because you won’t be going through a significant amount of calories. But if you go too hard and for too short a time period, those calories won’t be coming from fat.

When my wife was earning her biology degree, she had to go to the library and watch these outside-of-class lectures. In one of them, I distinctly remember the lecturer talking about how your body cannot process fat for energy without oxygen.

I don't remember what website I lifted this off of … so I apologize if it was yours.
I don’t remember what website I lifted this off of … so I apologize if it was yours.

“Aerobic” means “requiring oxygen.” “Anaerobic,” on the other hand, means, “requiring an absence of free oxygen.” It’s kind of silly, because you always need oxygen while exercising — it’s not as if you stop breathing to do an “anaerobic” sprint. But “aerobic” exercise is the only type of exercise that primarily taps into your fat by using oxygen.

I’ve only ever had one period of significant weight loss in my life — when I took up cycling. I started riding ~90 minutes three days a week. And I wasn’t taking it easy. I tried to ride the most consistent pace I could for the full distance — up and down hills, over soft dirt farm roads, into the wind and rain, and eventually back to my apartment. After two months or so of this regimen, someone told me I was looking kind of gaunt. So I finally stepped on a scale … and learned I’d lost 15–20 pounds over the previous two or three months.

It’s a delicate balance: riding, running, swimming or hiking hard enough to burn through lots of overall calories but doing it at a low enough intensity that a significant amount of those calories come from fat. If you need help keeping yourself in the right intensity, and this is an important point, buy a heart rate monitor and read this article by Mark Allen.

Now, again, I’m not saying you can never do high-intensity intervals. But I am saying you need to build up your aerobic metabolism for a few months … or years — to really take the time to achieve those adaptations we talked about earlier. That means that, for a while, yes, I want you to stay away from intervals and high-intensity stuff. Just build up your aerobic system. Then, when you come back to doing intervals, the adaptations will be in place for you to burn through more fat while you’re doing them.

So let’s recap on our action item for just a second:

• Work out aerobically for 45–90 minutes at least three days a week (preferably four or five)

That’s it. That’s all I’ve told you to do so far. Nothing else. That’s your foundation. If you do nothing else, do that. And for goodness’ sake, don’t tell me exercise doesn’t work for you until you’ve done that for AT LEAST 6 months — yes, six months!

Is this everything I have to say about weight loss? Not at all. There’s more where this came from. But this is probably enough for now. I’ll give you the rest in another blog post soon.

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One thought on “Exercise & Weight Loss

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