Why Low Carb Diets Don’t Work For Triathletes

The Greedy Bastards in the Diet Industry are Not Your Friend

The weight loss industry is worth $72 billion. This behemoth sector includes everything from fad diets touted in best selling books to weight loss pills, “cleanses,” and gym memberships. Unfortunately, the rapid growth of the diet industry has seemingly little impact on Americans’ waistlines. 40 percent of American adults are obese, while another 32 percent are overweight. The rest of the population isn’t doing so well either; 90 percent of American men are “overfat,” according to a recent study. Overfat is a fairly new term that encompasses everyone whose health is impacted from excessive body fat (from the morbidly obese to those who are just a little leaner than overweight). Apparently 76 percent of the world falls into this category. In short, there is a large and growing market for the diet industry to push its untested and unproven diet schemes upon. And, because businesses require a never ending cycle of new products (thanks capitalism), the “optimal diet” is always changing, causing confusion and failed weight loss attempts. Which is a good thing for the weight loss industry, since its market never shrinks…no pun intended. 

Confused Athletes

It’s understandable that triathletes, runners, and other endurance athletes get sucked into these fad diets, because not only is extra weight undesirable for health reasons and societal expectations, but extra fat simply slows us down. It reduces our body’s ability to cool off during exercise, slows our run pace by 1.5 to 2.5 seconds per mile (per pound of excess weight), and increases our surface area in the water, to name a few of the downsides. Because of this, many athletes alter their diet as a way to shed minutes and seconds off their times, or to simply look and feel better. Eating low carb is the cool thing to do these days, and pseudo science even touts it as a way to increase athletic performance, when in fact eating low carb is harmful for every type of athlete, from weightlifters to marathoners. For the purpose of this article, “low carb” refers to any diet with less than 30 percent of total calories coming from carbohydrates. 

The Thermal Effect of Food

There is some efficacy behind low carb diets like Atkins, Ketogenic, and a low-carb paleo. It takes more energy for our bodies to digest protein than fat or carbohydrates, according to Precision Nutrition. 20 to 30 percent of calories in protein are used up just digesting it, compared to five to 10 percent for carbohydrates and zero to three percent for fats. This high thermal effect of protein is one of the reasons why low carb diets work (for a while anyway). Protein and fat also fill you up more than carbohydrates, and it’s pretty difficult to eat packaged junk food if you’re strictly staying away from sugar. Many people on low carb diets are successful in losing dozens of pounds in a relatively short period of time, though keeping the weight off is difficult for a number of reasons, particularly because eating a very strict low carb diet for the rest of one’s life isn’t very practical. It is not only impractical as an athlete, but detrimental to your performance and longevity in the sport.

As an Athlete, Weight Loss is Not Your Primary Goal

Having the energy to train is your first priority. Your goal as a competitive triathlete, cyclist, or runner should never be weight loss first and performance second. Some runners and cyclists in particular have a hard time remembering that the main reason they wanted to lose weight in the first place was to run or ride faster. Having a large calorie deficit, or depriving themselves of carbohydrates, is a great way to ensure that the end goal of better performance doesn’t happen. Dieting for weight loss or doing drastic experimentation with diets for performance should be taken on very carefully, preferably with the help of a nutritionist or coach. 

Your Body Can’t Burn Fat as a Fuel ALL the Time

During a half-distance triathlon, you’re constantly in and out of your threshold zone for four or more hours.

Some athletes get brainwashed into thinking that by going on the Keto diet, their body can be magically trained to burn stored fat as a fuel at all intensities, thereby allowing them to go without food for long rides or even during races. To put it politely, this is bullshit. Our bodies are always burning stored fat and carbohydrates (stored in the form of glycogen), at all times, even during sleep. For example, when you’re at rest sitting in a chair watching TV, you’re mostly burning fat as a fuel (though your brain only ever uses glycogen). When you’re riding at a low intensity, you’re still mostly burning fat if you’re well trained, but you’re still burning some glycogen. The higher the intensity, the more glycogen you use.

Even if your body is super efficient at using fat as a fuel source due to lots of endurance training, you can’t get it to burn fat as the main fuel source as you approach threshold because your body needs to conserve oxygen for working muscles, and breaking down glycogen requires less oxygen. And, because you spend a lot of time at or close to threshold in races, you will never be able to forgo carbohydrates during a race, even if you’re on the keto diet. 

This will not help you during your next 20-minute threshold test

Signs That You Aren’t Eating Enough Carbohydrates

As an endurance athlete, you need a good mix of fat, protein, and carbs, as well as an extra heavy dose of micronutrients from vegetables and fruit. But Karbs are King in the world of endurance sports. You should be getting about half of your calories from carbs alone during heavy periods of training, if not more (upwards of 65 percent). Consuming too few carbs during hard training blocks will cause the following:

  • Decreased immune system resulting in constant sickness;
  • Low testosterone levels;
  • Fatigue;
  • Difficulty with high intensity workouts (threshold or above) due to low glycogen stores;
  • Frequent bonking;
  • Poor ability to recover from sessions;
  • Brain fog; and
  • Irritability. 

So basically just the normal results of hard training, exacerbated. 

Bonking Hurts Your Immune System, Testosterone Levels, and Central Nervous System

If you don’t replenish your glycogen stores after a workout (which can only be accomplished by eating carbohydrates) you run the risk of having decreased performance during your next session. This is particularly true if you don’t fuel well with carbs before or during your next workout. Even worse than slogging through a workout with low energy is bonking, which occurs when you’ve fully run out of stored glycogen. Bonking only happens during longer workouts (generally two or more hours) and/or if you do multiple sessions per day and you don’t properly refuel in between. The sensation is probably familiar to you—extreme weakness, intense hunger, confusion, hot and cold flashes, excessive sweating, blurred or cross-eyed vision, and a general feeling of hopelessness.

A bonk causes extreme stress on your body even if you get home quickly and chug 40 ounces of soda. Bonking wrecks havoc on your immune system, opening you up to the possibility of a cold virus; is extremely harmful for your testosterone levels; and beats the shit out of your central nervous system, causing excessive fatigue and negatively impacting workouts over the next few days. Bonking is pretty easy to avoid if you fuel well with carbs before each workout, during each workout, and after each workout. Yes, a bonk might make you skinnier, but only because you’ll be throwing up from the flu for three days afterwards.

Bringing along 10,000 calories of Clif Bloks is one way to ensure your ride is bonk-free.

Be the Beast is Here For You!

If you want to lose weight, get faster, or just generally be healthier and perform better at life, the Boulder, Colorado coaches at Be the Beast Coaching are here for you. Your optimal weight loss diet may be lower in carbs than someone training 25 hours a week (maybe 35 percent of your calories from carbs, for example), but going on a true low carb diet would be disastrous for your performance as a triathlete and we want to help you avoid that. Whether you have years of experience or are just getting started, we’re confident that we can help you reach your nutritional and athletic goals. Contact us today for a free consultation by clicking here

Postscript: Go Eat a Loaf of Bread

In the past, Kennett fell into the habit of avoiding bread, rice, pasta, and other high carb foods simply because of the calories. As a larger cyclist, he was always trying to cut weight to make it up the climbs, and eating a bowl of vegetables with chicken versus a cup of rice with chicken was just as filling but contained much fewer calories, so he usually opted for the former. As a triathlete, he began eating more calories because weight doesn’t matter as much due to the flat nature of the courses, the lack of pack dynamics, and the absence of true drafting, allowing the effort to be more steady—going one minute faster on a climb won’t make or break your race. Anyways, once he became a triathlete, a bike racer friend of ours hammered home the fact that he wasn’t eating enough carbohydrates. He probably didn’t have enough information to really know this for sure, but he’s heavily opinionated and likes to make quick conclusions. Turns out he was probably right. “Go eat a loaf of bread, dude,” he scolded Kennett after Kennett had complained about being tired. “Eat a loaf of bread a day. You need those carbs and bread is the only way to get enough.” It’s not the only way to get enough (you can choose rice, oats, potatoes or a hundred other things) but the “go eat a loaf of bread” thing stuck with both of us. Hopefully it sticks with you too. When you’re feeling run-down and tired, have an extra hard or intense few days of training, or are tapering for a race, go eat a loaf of bread (or part of a loaf). You might feel better. 



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