How To Maximize Your Body's Ability To Use Fat For Fuel

Fascinating:

"When Torbjørn Sindballe was a professional triathlete, he used the most cutting edge science to make himself the best triathlete he could be. His efforts helped him break the bike course record at the Ironman World Championship, as well as place third there in 2007."

Unfortunately he discovered that some of the difficulties he had as an athlete were due to a congentical heart defect. That discovery ended his career.

But in the meanwhile, he made some interesting discoveries:

"...The easiest way to improve your ability to oxidize fat—turn fat into energy—is to train for long hours on the trails or in the saddle at a relatively slow pace. Generally, you don’t want to go much faster than your Ironman pace if you’re trying to stimulate your fat oxidation capabilities. While most athletes are well aware of this, there are several diet and training tricks out there that claim to increase the quality of the training stimulus these rides and runs provide. I have researched and tried most of these tricks myself while I was an Ironman pro and now have an understanding of what does and doesn’t work.... 

"...I tested the Paleo diet over a six-month period. While the challenge of eating 4,000 to 6,000 calories a day from a diet composed of only fruits, vegetables, meats and nuts was outweighed by the feeling of being super healthy, I did not see any gains in my performance. I kept my endurance, but over time I felt the upper end of my power and recovery fade as I had difficulty replenishing the calories I burned. For athletes with more balanced workloads, the Paleo diet might work fine, but for an Ironman pro with 25 to 40 hours of weekly training, it became insufficient. In other words, I have doubts about its performance potential and have yet to see a study that proves it enhances the body’s ability to burn fat....

I haven't seen any evidence that the Paleo diet "enhances" your ability to burn fat. And if I were a pro triathlete, I'd be eating some dairy and some more animal fats (like pemmican) as sources of high-calorie fats... Which is what I do now.

...After trying out the Paleo concept, I became interested in how my diet affected which fuels—carbs, fat or protein—my body used. I discovered that it is possible to shift our metabolism to burn mostly fat, but we need to eat excessive amounts of fat to do this. That is, up to 60 percent or 70 percent of our daily calories would need to be from fat—a percentage far above what the Paleo diet recommends. Despite the shift in metabolism and fat-burning capabilities, a high-fat diet has no effect on endurance performance, a review of studies by B. Kiens and Burke in 2006 concluded. What’s more, the diet diminishes one’s ability to do intense workouts, surges and sprints as well as the ability to adapt to training if the diet is maintained over a long period of time. These results, along with high-fat diets putting one at risk for developing severe malfunctions in metabolism, suggest that this approach should be categorized as a “useless tool.”

It appears that he was following Cordain's initial conception of a Paleo diet, which I think was overly-limiting and misguided in several ways. I have never seen any evidence that a high-fat diet results in "severe malfunctions in metabolism", or "diminishes one’s... ability to adapt to training"; to the contrary, it's been shown to be completely safe. So I'm not writing it off as "useless" based on this.

"...Inspired by the research, throughout 2007 I did several tests in which I ate a high-fat diet for five to six days followed by two days of carbo loading—I felt one day of carbo loading was too short for the glycogen tank to completely refill. Subsequently, I did a solid Ironman where I felt great the entire way—something that hadn’t happened in years—when I won the Vikingman in Fredericia, Denmark, in early August. I used the same protocol leading up to the Ironman World Championship in October, where I once again felt strong on the later part of the race and made the podium for the first and only time in my career...."

This sounds very similar to the approach used by Jonas Colting, who still eats roughly "Paleo", and has had a very successful career. However:

"...Despite achieving the best results of my life, I was still unconvinced about periodized diets, given there were other possible causes for my breakthroughs. I wanted proof, so in the spring of 2008 I hooked up with Danish scientist Lars Nybo Nielsen and Team Danmark to test the diet. I already had a natural fat-burning rate of 0.8 grams per minute at Ironman pace while taking in carbs during the test—higher than anyone in Carey’s study, even after his test subjects ate a high-fat diet for five to six days. The highest rate of fat burning achieved by the cyclists in Carey’s study was 0.7 grams per minute. In fact, my natural fat burning rate was on par with the highest fat oxidation rate cited by Tim Noakes in Lore of Running. During the days of eating a high-fat diet, I reached a fat-burning rate of 1.2 grams per minute at Ironman pace, confirming the theory that a high-fat diet shifts your body’s reliance on fat for fuel, but my rate shifted back down to 0.8 grams per minute after two days of carbo loading. It seemed the protocol had no effect on me...."

That's a fascinating bit of information. Eating carbs prior to the race significantly reduced his rate of fat burning. It wasn't that the protocol had "no effect", it was that insulin reduces the rate at which the body will produce fat. The effect was the expected one. I think carb-loading is probably not a good idea for this reason, unless your metabolism is super-flexible, and able to switch from one fuel to another quickly.

"...One could speculate that my fat burning ability was already high and that this strategy has the greatest effect on individuals who aren’t as fit as I was or that the two days of carbo loading was too much. I should also note that such a sudden switch in diet puts you at risk for constipation and other digestive problems. Despite the results of my personal study, I decided to use the periodized diet again before Kona in 2008, because it had been successful the year before and it might have an effect on the size of my glycogen stores that we had not yet been able to detect. Unfortunately, the risks caught up with me as my digestion literally stopped the Friday before the race until I was back home five days later. This mistake cost me dearly in the lava fields....

I wish he specified which type of carb he'd loaded with. I could see a pasta dinner having this effect, due to the toxic properties of wheat, but I've gone from days of low-carb eating to a meal with a lot of white rice with no ill effects whatsoever. At any rate, I don't think carb-loading's a great idea, but it shouldn't be this problematic to your gut. But then he discovers:

"...While Paleo, high-fat and periodized diets have little or no effect on enhancing one’s endurance, there is a less risky tweak you can implement in your training to improve your ability to burn fat for fuel—regular rides on water. I began to implement them back in 2007, and at first I could scarcely go for one-and-a-half hours before I bonked. But as my body adapted, I was able to ride three, four or five hours on water alone. This approach has a big effect in activating the genes that stimulate the production of enzymes involved in fat oxidation, as shown in a 2005 study by L.J Cluberton et al. In other words, the water-only rides might be the reason my ability to burn fat was already so high when I did the periodized diet experiment.

"If you decide to implement these water-only rides in your training, remember that these rides are depletion sessions, which leave you drained, and should always be followed by recovery days. During my Ironman building period, I had to work hard on consecutive days, so I did a modified version of these water-only rides that allowed me to maximize the stimulation of fat oxidation without requiring so much recovery. In short, I would do the first two hours of every training session on water alone and then add slowly absorbable, solid carbs, such as whole grain sandwiches or oatmeal-based energy bars. This process kept my blood sugar levels in check so I avoided bonking and could keep the intensity up late in the sessions. But at the same time this allowed my body to predominantly use fat for fuel, and it stimulated enzyme production. Early in the year, when intensity was more important, I would fuel rides from the start and only do a water-only ride once a week.

"My scientific team and I tested the water-only approach and found that during these rides, I would burn fat at a rate of 1.2 grams per minute—similar to the fat burning rate I achieved after high-fat eating on my periodization diet. This indicated that the training stimuli of the water-only rides were the same as those in a high-fat diet...."

Based on Jimmy Moore's interview with Tim Noakes, I think it's a little too soon to write off a low-carb, paleo diet as a fueling strategy. (And I'll definitely be skipping the "whole grain sandwiches".) Unless his "scientific team" was pretty cutting-edge, they were probably steeped in the idea of the supposed necessity of carbs. But the water-only (fasted, essentially) training runs are a great idea, I think. Fasted training sessions also cause the body to increase glycogen stores.

They don't have to leave you depleted, either. If you do them at your Maximum Aerobic Fitness pace, you'll feel just fine afterwards, in my experience. And not just my experience. As Mark Allen, one of the greatest triathletes put it:

"On top of the speed benefit at lower heart rates, I was no longer feeling like I was ready for an injury the next run I went on, and I was feeling fresh after my workouts instead of being totally wasted from them."

The only drawback of a high-fat, fat fueled training program is that if you're starting out of shape, it takes time to retrain your body. There is no short cut that I'm aware of.