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The main focus of Ironman training and racing is on improving metabolic efficiency—which is nothing more than training the body to use aerobic energy systems at the highest paces and/or wattages possible. Being metabolically efficient is the least costly way to fuel the body during exercise.
There’s a great deal of debate on how best to develop this. Most would argue that training at intensities right around aerobic threshold (AeT) is the most effective method. A recent push, however, makes the argument that dietary changes can impact these adaptations; “starvation workouts,” or sessions where athletes essentially starve themselves in an effort to force the body to use fat as its fuel source, are gaining some traction. In my opinion, the research on this practice is very uncertain, and is accompanied by a great deal of potential detriments—none of which make it an acceptable risk. Here are some of the risks an athlete is facing when they engage in such workouts:
1) Starvation workouts can be extremely catabolic, as the body is forced to attack lean muscle mass in order to create carbohydrates for fuel. (Catabolism is the breakdown of complex substances into simpler ones.) This process of gluconeogenesis (when glucose is produced from non-carbohydrate sources like fats or proteins) is nightmarish for lower BMI athletes (who are already limited in strength), and older athletes (females older than 45 and males older than 50), who, because of age, have difficulty maintaining lean muscle mass. It’s an assault on the body that disintegrates muscle mass and exacerbates an already problematic limiter. Furthermore, depriving the body of the fuel that it needs to train over long durations can set the stage for a compromised immune system, leading to illness, and of course, missed training sessions.
The possible benefits of these workouts simply do not outweigh the potential risks.
2) Starvation workouts create the prime atmosphere for bonking. Be it a typical training workout or race day, bonking should never happen. Your workout will likely be limited by a lack of fuel before the body can be appropriately taxed and trained. This conflicts with the reason why we do all this training in the first place. The goal of any workout should be to promote an environment where the athlete can complete better and better workouts, pushing previous limiters, and increasing fitness. We make too many sacrifices aimed at improving our fitness already to allow something we have 100% control over to further limit us.
3) At the Ironman distance, training the gut to be able to absorb nutrients is part and parcel of executing a race plan. Starvation workouts don’t allow us to train this very important limiter, and we end up seeing athletes forced to walk because they haven’t trained their bodies to process the calories required to race effectively. As the coach of some of the fastest Ironman marathoners in the professional and age group ranks, I can tell you how important it is to practice your race fueling strategy every single day in training. (I can’t, however, even begin to tell you how many Power Bars and Power Gels my athletes consume throughout the year!)
I’ve always believed that the best way to approach limiters in triathlon is to first deal with those that exist in series with one another. For example, how well an athlete has fueled their race doesn’t typically become apparent until the run. With this in mind, and knowing that an athlete’s inability to handle their race nutrition is what typically undermines their Ironman, I try to first focus on this limiter as it typically occurs earliest in the chain of events. It really doesn’t do much good to focus on a limiter that occurs further down the line, since it may never have the opportunity to actually become a limiter on race day.
An athlete’s metabolic efficiency, on the other hand, is typically a limiter that appears in parallel with most of his or her other limiters—an athlete’s race will seldom come to a screeching halt due to poor metabolic efficiency. Therefore, not until we are 100% certain that an athlete doesn’t have a nutritional limiter should we begin to even consider unorthodox ways of improving metabolic efficiency.
If you insist on incorporating starvation workouts into your training, I recommend trying it no more than once a month, and not until you have full confidence in all aspects of your training, racing, and fueling. There simply has not been enough research published on the topic for me to feel confident endorsing it. The possible benefits of these workouts simply do not outweigh the potential risks.
Jesse Kropelnicki founded QT2 Systems, LLC; a leading provider of personal triathlon and run coaching, as well as TheCoreDiet.com a leading provider of sports nutrition. He coaches professional athletes Caitlin Snow, Dede Griesbauer, Ethan Brown, and Tim Snow, among others. You can track his other coaching ideas on his blog at www.kropelnicki.com.