Research Review

Diaz EO et. al. Glycaemic index effects on fuel partitioning in humans. Obes Rev. (2006) 7:219-26.

The purpose of this review was to examine the role of glycaemic index in fuel partitioning and body composition with emphasis on fat oxidation/storage in humans. This relationship is based on the hypothesis postulating that a higher serum glucose and insulin response induced by high-glycaemic carbohydrates promotes lower fat oxidation and higher fat storage in comparison with low-glycaemic carbohydrates. Thus, high-glycaemic index meals could contribute to the maintenance of excess weight in obese individuals and/or predispose obesity-prone subjects to weight gain. Several studies comparing the effects of meals with contrasting glycaemic carbohydrates for hours, days or weeks have failed to demonstrate any differential effect on fuel partitioning when either substrate oxidation or body composition measurements were performed. Apparently, the glycaemic index-induced serum insulin differences are not sufficient in magnitude and/or duration to modify fuel oxidation.

My comments: Talk to any of the bodybuilding guys and they'll tell you flat out that high GI carbs are the work of the devil. Except maybe after workouts. High GI carbs are said to spike insulin, make you fat, contribute to social and moral decay and are probably involved in the high gas prices.

And yet, controlled studies don't bear out that belief, which is what this review examined. Looking at research from short-term (single meal) to long term (weeks), it found that the differences in insulin response to diets of different GI (especially within the context of mixed meals) had literally no impact on overall fuel utilization or storage. The researchers succintly conclude "Taking into account all of the above arguments, we speculate that under postprandial (my note: after meals) conditions, GI-induced serum insulin differences are not sufficient in magnitude and/or duration to modify fat oxidation."

So why do some other studies find that high GI carbs make you gain weight/fat: because many people eat more calories when they eat higher GI carbs. And eating more tends to make you fat compared to eating less. This is the typical confound that leads people to draw stupid conclusions: under uncontrolled eating conditions, people tend to eat more or less given certain food types (since most bodybuilders watch calories like a hawk, that kind of research does not apply to them). But it's not a GI thing per se, it's because for some people, eating higher GI carbs makes them eat more and eating more calories makes them fat. Under controlled calorie conditions, especially within the context of mixed meals, GI would appear to be almost entirely irrelevant. So quit obsessing about it and start enjoying your life, instead of worrying about whether one food is inherently 'better' than another because the GI is 10 points lower.

Feature Article:

Steady State Aerobics vs. Interval Training Part 1

In recent years, there has been quite the overpopularization of the concept of interval training, along with a rather major backlash against traditional forms of aerobic training, for fat loss. It's not uncommon to read how low intensity aerobics is useless for fat loss, everybody should just do intervals, regular aerobics makes you lose muscle, etc. I have seen it claimed that aerobics will make you fatter, stress the adrenals, and all manners of fascinating claims. Nevermind that, over the decades, bodybuilders have gotten into contest shape with (often endless amounts of) cardio, runners, cyclists and swimmers are extremely lean, etc. Somehow, aerobic training has gotten a bad rap.

I think what happened is that for about 2 decades, aerobic training has been (over) emphasized over all other kinds of activity. As well, people got the absolutely wrong idea about how to use it for fat loss so you have people trotting along on the treadmill at an intensity that is just slightly higher than sitting on the couch, burning a couple of hundred calories in an hour and wondering whey they aren't losing fat.

So folks, usually with a heavy resistance training bias or background, overreacted. And the backlash began. Basically, people get a little over-enthusiastic about a certain type of training (or eating), take it to some absurd extreme, get into problems, find an alternative and decide that the first type of training is useless, overrated, etc, etc, blah, blah, blah and they jump to the opposite extreme. They jump from one extreme to the other until, hopefully, they come back to some happy medium.

Well, I'm a happy medium kind of guy and I try to avoid that kind of binary either/or thinking; I find it more useful to examine training tools in terms of their pros and cons, benefits and disadvantages. So let's examine both steady state aerobics and interval training for fat loss (endurance performance is a separate topic) in that fashion. In part 1, I'm going to define some terms and examine both types of activity; in part 2 (two weeks from now), I'll talk about how to decide which is best depending on the specifics of the situation

Some definitions

Steady state training: Any form of aerobic/cardiovascular training where some reasonably steady intensity is maintained for an extended period. So this might be something akin to 20-60 minutes at a steady heart rate of 140-150 (could be higher, could be lower). I'm just going to call this cardio or aerobics, even though I know some people get into longwinded semantic arguments about it. I'm sure everybody knows what I'm talking about.

Interval training: Essentially any form of activity that alternates higher intensity activity (such as 30-60 seconds almost all out) with periods of lower intensity activity. The rest interval can be passive (sit on your butt) or active (keep moving at a low intensity). While weight training can technically be considered interval training, I'm going to restrict this article to interval training done with standard cardio modes (i.e. running, cycling, stairmaster, etc). A typical interval workout for fat loss might be a short warmup followed by 5 repeats of 60 seconds near maximum intensity alternated with 60-90 seconds of very low intensity activity, followed by a 5' cool down. This is often referred to as high intensity interval training (HIIT) which differentiates it from aerobic interval training discussed immediately below.

Aerobic interval training: For completeness, I want to mention a third, sort of hybrid, form of training that is usually referred to as aerobic interval training. This is a type of training often used by very untrained beginners who are simply unable to perform 20 minutes or more of continuous aerobic activity. So they might perform 5 minutes of low intensity aerobic activity prior to taking a short break, followed by another 5 minutes of low intensity aerobic training, until they accumulated 20-30 minutes of activity. Over their first several weeks of training, they would try to increase the duration of each aerobic interval session while decreasing the rest interval. Additionally, many strength and power athletes do a type of aerobic interval training usually referred to as extensive tempo running: this is a low intensity type of aerobic interval training done in short bouts. So a sprinter might run 10 repeats of 200 meters but at a very low intensity (aerobic intensity) with 100 meters of walking in-between. In this article, I'm not talking about aerobic interval training when I compare and contrast traditional aerobic training and interval training; aerobic interval training is sort of a third category that doesn't apply to this discussion.

Moving on

Ok, so now that we're on the same page definition wise, I want to compare and contrast aerobic and interval training in terms of potential pros and cons. This will allow us, in part 2 (two weeks from now) to look at how to integrate the different types of training into real world workout schemes.

Steady state aerobics

Pros:

1. Depending on the intensity, steady state aerobics tends to burn more calories during the exercise bout than interval training.

2. More appropriate for beginners.

3. Can be done more frequently, daily or more often (if desired) although this depends on the duration, intensity and frequency as well as the setup of the rest of the training program.

4. Some research finds suggests that regular exercise helps people stick to their diet better. In that interval training can't (well, shouldn't) be performed daily, low intensity activity may help people stay on their diets.

Cons:

1. Most indoor aerobics modes tend to be boring, especially for long durations. Exercise can, of course, be done outdoors but this raises a whole separate set of issues (bicycle safety, running outdoors, traffic, etc) that are beyond the scope of this article. This is a big part of why gyms have music and televisions; I have seen one with a cardio movie theater.

2. An excess of endurance training, especially at higher intensities (too close to lactate threshold, a topic for another newsletter) seems to cause muscle loss, decrease strength and power, and cause overtraining. This is major issue for bodybuilders and strength/power athletes but can be avoided by keeping the intensity under control.

3. Too much repetition of the same mode of aerobics can generate overuse injuries, both runners and cyclists are prone to knee problems, swimming causes rotator cuff issues (and the cold water tends to increase hunger), etc. This can be avoided by non-endurance athletes by rotating the type of activity being done.

4. Unless people are tremendously aerobically fit, it can be difficult to burn a huge number of calories unless the duration of each workout is just ridiculous. So, at moderate intensities, the average person might burn 5-10 calories/minute; a 145 lb person burns about 100 calories per mile walking or running. So over an hour aerobic session, you might achieve 300-600 calories burn. While this can certainly add up if done daily, it's still a fairly small expenditure. The people trotting along on the treadmill or spinning on the bike at low intensities, often for only 30 minutes, are burning jack all calories. Which are usually more than compensated when that person figures that they must be burning at least 1000 calories and rationalizes that cheeseburger and milkshake because of it. This is one of those weird ironies: very high caloric expenditures through aerobics are reserved for trained endurance athletes, and they typically don't need it. The people who need to be burning a lot of calories through aerobic activity usually aren't able to, at least not initially.

Before continuing, I should probably bring up one of the more idiotic arguments against steady state aerobics here. The argument goes something along the lines of "Aerobic training is useless because, as you adapt and become more efficient, the same workout that burned a significant amount of calories over 40 minutes takes 60 minutes because you're getting more efficient." This is about as logical as saying that weight training is ineffective because the same weight that was difficult for 12 repetitions is now too light, and you have to do more repetitions with it. Except that, in the case of weight training, the suggestion would be to add weight to the bar. And the same exact thing can be done with aerobic training: as the body adapts (and you become fitter), you can increase your caloric expenditure by increasing the intesity of your workout. So say that you were doing the stairmaster at level 8 and a heart rate of 140 beats per minute for 40 minutes. Now you've adapted and level 8 is only a heart rate of 130. Well, you could go to an hour, or you could increase the intensity to level 9 and burn more calories during those same 40 minutes. In addition, exercise efficiency doesn't vary that much; in cycling for example, it varies between about 20-25%. So even if you increase your efficiency by 5%, this would only change the caloric expenditure for a given exercise bout by that same 5%. A 400 calorie workout becomes a 380 calorie workout. This is hardly a change worth decrying steady state aerobics before.

Interval training

Pros:

1. For a given time investment, interval training leads to a greater fat loss and this occurs despite a smaller calorie burn during activity. This is because interval training generates a much larger EPOC (excess post-exercise oxygen consumption) which are the calories burned post exercise.

2. Interval training may improve the muscle's ability to use fat for fuel more effectively than aerobic training (note: recent studies have also suggested that interval training can generate very rapid improvements in endurance performance in a very short period but this is beyond the scope of this article).

3. Time efficient: Not everybody has the time to devote to an hour (or more) of aerobic training per day. A properly set up interval workout may only take 15-20 minutes.

4. Time seems to pass faster: Compared to regular aerobics, which can be mind numbingly dull (especially if done indoors), the change in intensity with intervals seems to make the workout pass faster.

Cons:

1. The intensity of intervals makes them inappropriate for beginners. One exception is a style of training called aerobic intervals which I mentioned above. But high intensity interval training is simply inappropriate for beginning exercisers, for the same reason that high intensity weight training is inappropriate.

2. Intervals are high intensity training, this has implications for the overall training setup (discussed in more detail in part 2) and integration with the rest of your program (i.e. weight training). Simply put: if you think you can train legs in the weight room 2-3X/week and do intervals an additional 2-3X/week on alternate days, you are incorrect unless you are deliberately trying to overtrain or get injured.

3. Higher risk of injuries: this depends somewhat on the type of activity with high impact activities such as sprinting carrying a higher injury risk (especially for heavier individuals) than intervals done on the bike or stairmaster.

4. Limited in how many days they can be performed. Two to three days per week is about the maximum for interval training, most endurance athletes won't do intervals more than twice/week. Have I heard of people trying to interval daily? Yes. Do I think it's a good idea? No.

5. Intervals hurt, especially intervals in the 60-90 second range where muscular acid levels are very high. If you're not willing to push yourself, you won't get much out of interval training. You know the warnings on most aerobics machines, that tell you to stop if you feel signs of exhaustion or fatigue; that's what a properly done interval program should feel like. Sensations of burning in your legs (from high acid levels in the muscle) along with extreme discomfort are not only common but expected. Some people also report nausea initially, this can be made worse if they have eaten too close to training.

In part 2 (two weeks from now), I'll examine some specific training situations to see which type of activity might be best under a given situation.

Questions and Answers

Q: If you could design a routine from only 4 exercises, what would it be?

A: In the most general terms, I'd pick one leg movement, one compound pushing movement, one compound pulling movement. This would leave one tinkering movement which would probably be a core exercise. If someone had the experience, I might put in a quick lift (power clean or snatch or full squat clean or snatch). That would leave scant little of the important stuff unhit.

For legs, I'd pick from full squat, deadlift, front squat or even leg press.

For compound pushing, flat or incline bench, even overhead press.

For compound pulling, rows, pulldowns or chins.

For tinkering, it would kind of depend on the other exercises chosen.

So some good full body workouts would be

Full squat, Incline bench, chinup

Deadlift, flat bench, rows

Leg press, incline bench, row.

you get the idea.

Q: Do things like free/cheat meals, refeeds or diet breaks play a role for the general dieter on a typically non-retarded diet or are they only for hardcore athletes and bodybuilders?

A: I am of the firm belief that everyone can benefit from taking breaks from their diet, athlete, bodybuilder or general public dieter alike. Research into rigid and flexible dieting has found that the folks who are more strict/rigid with their diet tend to weigh more, binge more and do worse on their diets. Essentially, being too strict with their diets make things worse.

It's simple human nature: tell someone that they can't ever have something again and, odds are, it will make them want it that much more. So tell someone that they can never eat bread again and they will crave it. Simply knowing that, from time to time, they can have some of the 'forbidden' foods (and I put that in quotes because I don't think any food should be considered forbidden or bad; it's all a matter of application) will make them want it.

This is the topic of my book A Guide to Flexible Dieting, it discusses how being too strict with your diet can make it backfire and explains how using free meals (where you break your diet for a single meal), structured refeeds (periods of deliberate carbohydrate overeating), or full diet breaks (two week periods where you go off of your diet completely) can be used to increase your odds of succeeding on your diet this time around.

Like the Rapid Fat Loss Handbook, the Flexible Dieting guide sets up recommendations based on your current bodyfat percentage and activity level and gives specific recommendations for all three approaches: free meals, refeeds and how often to take a full diet break.

Q: Is fasted cardio the only way to burn fat?

A: Of course not and this is one of the sillier ideas that has come out of bodybuilding lore, propagated by people who, quite frankly, should know better. The basic idea is that, under fasted conditions, with blood glucose low and blood fatty acids high, the body will burn more fat for fuel. This is, roughly speaking, true.

However, the entire idea is predicated on a basic misunderstanding of physiology in the first place: that what you burn during the activity makes much of a difference in what you lose fat wise.

Consider that the studies on interval training (during intervals, you burn almost exclusively carbohydrate) show greater fat loss, despite little to now fat burning during activity. Why is that? Well, because you burn fat afterwards.

Sprinters are generally the leanest of all the athletes, and they literally never burn fat during their workouts; they burn carbs. And they still stay lean.

Other studies looking at an equal number of calories expended during different intensity activity (i.e. burn 500 calories at low intensity vs. 500 calories at high intensity) show essentially no difference in fat loss. For 99% of situations, it simply doesn't matter what you burn during activity. One exception, is females (or males) who are trying to get rid of the last bit of stubborn bodyfat. In my next book, I provide a number of different protocols to optimally reduce stubborn bodyfat, some of which utilize morning fasted cardio.

So the idea that, because you burn more fat under fasted conditions, you should do your cardio fasted to lose fat is equally nonsensical. Becuase it doesn't matter whether you burn fat or carbs during your workout; if you create a deficit, that deficit will be pulled from fat stores.

Add to that that most people can sustain a higher intensity of activity (burning more calories overall) doing cardio after they've eaten and you could probably make a (rather weak) argument for non-fasted cardio being more effective for fat loss.

Add to that possible issues with increased use of protein for fuel under fasted conditions and the idea that fasted cardio is the best for fat loss simply falls flat. I consider it another idiotic bodybuilder myth that has gotten propagated into the general public and accepted without thought.

At the end of the day, it probably doesn't matter: more important is that the cardio gets done/calories get burned. When you do it is less important than that you do it. You'll find uber lean cyclists who have never done a fasted cardio session in their life, and fatasses trotting along the treadmill first thing in the morning who haven't lost an ounce of fat in a year.