Research Review

Plourde M, Cunnane SC. Extremely limited synthesis of long chain polyunsaturates in adults: implications for their dietary essentiality and use as supplements. Appl Physiol Nutr Metab. 2007 Aug;32(4):619-34.

There is considerable interest in the potential impact of several polyunsaturated fatty acids (PUFAs) in mitigating the significant morbidity and mortality caused by degenerative diseases of the cardiovascular system and brain. Despite this interest, confusion surrounds the extent of conversion in humans of the parent PUFA, linoleic acid or alpha-linolenic acid (ALA), to their respective long-chain PUFA products. As a result, there is uncertainty about the potential benefits of ALA versus eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA). Some of the confusion arises because although mammals have the necessary enzymes to make the long-chain PUFA from the parent PUFA, in vivo studies in humans show that asymptotically equal to 5% of ALA is converted to EPA and <0.5% of ALA is converted to DHA. Because the capacity of this pathway is very low in healthy, nonvegetarian humans, even large amounts of dietary ALA have a negligible effect on plasma DHA, an effect paralleled in the omega6 PUFA by a negligible effect of dietary linoleic acid on plasma arachidonic acid. Despite this inefficient conversion, there are potential roles in human health for ALA and EPA that could be independent of their metabolism to DHA through the desaturation - chain elongation pathway.

My comments: So I had originally planned to look at a paper on BMR and Spontaneous Ph in response to varying combinations of diet and exercise but, after last issue's massive feature article, I'm not sure it would have added much.

Also, a question I received regarding a statement I made in the updated Rapid Fat Loss handbook about flax oil no longer being an appropriate essential fatty acid (EFA) source, along with some general confusion on various Internet forums about the topic made me choose this week's paper. I'm going to skip what I think is some unnecessary detail and complexity since I don't think it adds to the practicalities of the question I want to address.

By way of introduction, early nutrition research was very concerned with determining what were the essential nutrients for human health and survival. By definition, an essential nutrient is one that is

a. Required by the body for survival

b. Can't be made by the body

It's a bit more complicated than that and there are some nutrients which are defined as conditionally essential (glutamine is one) but this covers the basics.

Vitamins and minerals are essential, about half of the amino acids are essential and, as early research fought to determine, it turns out that some fatty acids are essential. These are called, generally, the EFAs and, as we now know there are two of them.

Due to methodological issues that I won't detail, determining what fatty acids were actually essential was actually a fairly difficult problem in the early part of the 20th century. In early research, it was thought that there were three EFAs, alpha-linoleic acid (ALA, not to be confused with alpha-lipoic acid, an insulin sensitizer), linolenic acid (LA), and arachidonic acid (AA). When it was found that rats could make AA out of LA, it was dropped, leaving two EFAs. I'd note that, at one point, it was thought that LA was the only EFA but, as we now know, both ALA and LA are essential fatty acids.

These two fatty acids are also often referred to by their chemical names (which have to do with their structure) which are omega-3 (n-3,w-3) for ALA and omega-6 (n-6, w-6) for LA.

Now, both LA and ALA are metabolized in the body (this includes a variety of processes including oxidation in the liver) to other compounds, I'll spare everyone the biochemical details.

LA is metabolized to gamma-linoleic acid and then eventually to arachidonic acid. As mentioned above, this is why AA was removed from the list of EFAs; since the body can synthesize it from LA, it's not essential.

ALA is metabolized to EPA (you don't want to know the full name) which is further metabolized to DHA (same comment). EPA and DHA are more commonly referred to as the fish oils since they are found in high amounts in fatty fish.

Now, for the most part, I'm not going to talk much about the LA->AA pathway. The reason is that excess LA/AA is actually detrimental to the body. AA has inflammatory characteristics and excess LA (esp. in relation to ALA intake) is thought to be a harmful to the body. I'd note that studies show that the current ratio of LA:ALA is around 25:1. It's thought that a ratio of 4:1 or lower would be better.

Bottom line, most of us get way too much LA in the first place, unless you eat essentially a zero fat diet you get most of what you need, there's no real need to make lots of AA from a health or survival standpoint.

Of more concern is the EPA/DHA issue which is what I want to discuss in more detail. Both are critical for things like optimal health, fat burning, etc. It looks like DHA may be even more important. Babies accumulate DHA in their brains and babies who either don't receive sufficient DHA (from the diet) or have a rare genetic syndrome can end up with brain damage. DHA is present in large amounts in cellular membranes. Basically, sufficient DHA intake is critical.

Which brings us to the real topic of this week's paper: Can the body convert ALA to EPA/DHA in sufficient amounts? Because, if it can, then using a source of ALA such as flaxseed oil is sufficient. If it can't, then intake of preformed EPA/DHA via fish oils is going to be required.

Now it's clear that the human body possesses the enzymatic machinery to convert ALA to EPA/DHA. But there is an issue of whether the conversion process can occur in sufficient amounts.

Without going into the ridiculous detail of this week's paper, the short-answer is basically "No, it can't." Now, there are some methodological issues with the studies having to do with the amount (giving large amounts of ALA can cause an underestimation of true conversion) given and some other stuff but the bulk of the data points to the simple conclusion that the human body is simply terrible at converting ALA to EPA/DHA.

In fact, studies using flax oil supplementation show no change in DHA levels. None. It will raise EPA a bit but the conversion to DHA is essentially zero.

There are two odd exceptions to the above that I want to mention. The first is in vegans. Due to zero intake of animal foods, they have zero intake of DHA. But while they show lower levels of DHA, they don't show deficiency symptoms. While more research needs to be done, presumably pathways of conversion/production of DHA are up-regulated under this situation.

The other is in extreme w-3 deficiency, where plasma DHA levels typically rise after ALA supplementation. This is just a classic feedback loop, and occurs for other nutrients as well (for example, absorption of certain minerals will increase the more deficient someone is). This probably explains why a lot of bodybuilders (eating nearly zero fat) did get something out of flaxseed oil during the 90's, in a massive deficiency, they got better conversion. Once that deficiency is fixed, conversion rates drop into the toilet.

But beyond that, the overall impact of ALA supplementation plasma levels of EPA is small, for DHA essentially nil. And given the critical importance of both EPA/DHA on human health, fat loss and performance, the bottom line is that this makes ALA (via flaxseed oil or what have you) an insufficient replacement for preformed fish oils.

As a couple of final comments, I'd also note that supplementation of EPA doesn't raise DHA levels either. Since all commercial fish oils I've ever seen contain both EPA/DHA, this is a fairly non-issue. But it is yet another reason why ALA by itself is insufficient. Not only is the conversion of ALA to EPA small, the conversion of EPA to DHA is simply nil, hence ALA won't impact on the body's DHA levels.

Having established that ALA intake is ineffective at increasing EPA/DHA levels, a final and related question to address is whether ALA has any effects above and beyond what EPA/DHA are doing. This week's paper mentions one possibility which is a mild impact of ALA supplementation on cardiovascular disease. It also notes that EPA/DHA supplementation has a greater effect. Other researchers (not all agree) feel that the true EFAs are EPA/DHA, and that ALA is simply a parent compound that is not essential in its own right. Currently I tend to agree with this stance.

Summing up: the body requires EPA/DHA for optimal function. This includes fat loss, prevention of a lot of diseases, controlling inflammation, etc. While the body has the machinery to convert alpha-linolenic acid (ALA, found in high quantities in flaxseed oil), the amount of that conversion is small for conversion to EPA and negligible for DHA. Hence I don't feel that ALA/flax oil is an appropriate EFA source. You need to be taking preformed EPA/DHA (in either capsule or liquid form). This was one of the changes I made to the second edition of the Rapid Fat Loss handbook (the first edition allowed for flax to substitute for fish oil).

Feature Article

Interval Training Versus Steady State Cardio Part 1

In recent years, there has been quite the over popularization 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.

On internet forums, folks who have been taken by this idea are often trying to intervals 3-6 times per week (if they do cardio, they will only do intervals and since many do cardio every day) on top of heavy leg training. And wonder why they can't recover. It's gotten way out of hand.

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 (next week), 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, stair master, 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 and duration 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, 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 intensity of your workout. So say that you were doing the stair master 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.

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 stair master.

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, I'll examine some specific training situations to see which type of activity might be best under a given situation.

Questions and Answers

Q: I'm a 33-year-old male at a weight of 285 lbs (38% bf). I've been enjoying your newsletter for sometime and I really like the principles in the Rapid Fat Loss handbook that I recently purchased. I haven't tried the plan because I'm a little hesitant with the Ephedra recommended. It's not that I don't believe the information that you mention regarding its safety; it's just that I've had atrial fibrillation and a history of palpitations as well. Is there something else that I could substitute for the stack? I tend to tolerate Hot Rox Extreme pretty well (not sure if that's ideal or not).

A: In a situation like this, where there is a pre-existing condition, I would absolutely not recommend ephedrine-based fat-burners of any sort. Additionally, and this is something I discussed (although not in massive detail) in the Rapid Fat Loss handbook, the more body fat someone is carrying, the less of a concern metabolic slowdown tends to be. So better to ditch the ephedra and do the diet without it.

Q: I purchased the UD2 book and I was very fascinated by this method, and was more fascinated as to how everything unfolded as was predicted. The only problem I had was the swing from carb deprivation to calorie mania, and I just couldn't maintain enough control during the carb-load to set myself up properly for the next cycle, but we'll see in the future.

I have a question for you. I did find this method helped me to build extra strength in my legs, and since I compete in triathlons, was very excited about this. How would this strategy work during the week of the triathlon itself? I typically spend Mon thru Wed resting, and then do some light roadwork on Thursday and Saturday prior to the event on Sunday. If I worked this method into the event week, it would seem to me that I would have a lot of extra strength by way of the higher concentration of glycogen for riding, running, and swimming, since the extra strength in my legwork in the gym was amazing. The sprint triathlon is primarily anaerobic in nature, as I'm working at 95% of my max hr for a majority of the event. Do you think this strategy would help my performance if I scheduled the end of my carb-load to coincide with the triathlon?? I'm very fascinated by this possibility, because strength in the triathlon is a disadvantage for me with the competition that's out here (I'm 5-8, 165, genetically ungifted and have a very average Vo2max, although very muscular)

A: There's been some interesting research on this topic and *some* athletes appear to respond favorably in terms of performance to fat adaptation prior to a carb-load, others do not. There was also one study suggesting that fat adaptation impaired sprint performance

If I were going to set up UD2 towards a competition event, I think the key would be to finish the fat adaptation and get through the carb-load with at least a day of normal eating before the event. This should give the body time to normalize skeletal muscle function prior to the event such that sprint performance isn't impaired.

So working backwards from Saturday (day of race)

Friday: normal eating, light to no training

Thursday: perhaps one final low volume intense workout prior to carb-loading

Wed-Sun: low-carbs for fat adaptation

So you fat adapt for 4 days, carb-load and then get one day of normal eating before the race

At least one runner on my forum reported using something like this and setting a PR in a 10k