The Paleo and Zone Diets have become very popular and many military athletes have chosen to go with low carb/high-fat diets to support their training. These diets can have some serious benefits, in terms of meal frequency, favouring animal proteins and whole foods etc. But, for the sake of this discussion, I’ll focus on the low-carb element. When it comes to a low carb/high-fat diet, the theory is one mole of fat produces more energy (ATP), than one mole of carbohydrates. The idea is if we can train our body to become fat adapted and use fat as its main fuel source, we can go longer, harder, faster.
There are several issues with this theory.
First, while fat does indeed produce more ATP than its equivalent in carbohydrates – because it takes longer for a fat molecule to move through Kreb’s Cycle and convert into ATP – this technique isn’t ideal for glycolytic training (i.e. that which requires sugar, the building block of carbohydrates – as a fuel source). It’s also not ideal when utilizing a training program that contains high volume of both endurance training, strength training, and strength endurance training.
The second is that these diets are based on theory, not results. In theory, low cab/high fat is a pretty good idea. BUT, after working with hundreds of athletes, and talking to my colleagues who’ve worked with thousands more combined, we’ve seen NOTHING but poor results on low-carb diets for the vast majority of tactical athletes.
The third issue is that fats are difficult to digest during exercise. Recent research has suggested that athletes can consume and use up to 90g of carbs per hour so long as there is a 2:1 ration of glucose:fructose. Fats are not easily digested during exercise.
The fourth issue is that even when fats can be digested, they will not replenish muscle glycogen levels – which are essential to aerobic performance. If an athlete switches to a low carbohydrate diet and are in control of their training regime then a low carb diet may work for them. When your training consists of dozens of hours of training per week, performing multiple sessions a day to prepare for two weeks of hell – you need to refuel, and you need to teach your body to refuel. Like it or not, on selection you are going to be eating military rations that are high in carbohydrates and your body better be used to it.
Do low-carb diets have a place in long-term health, longevity, mental acuity and disease prevention? Yes. But, from a goal-specific perspective, supporting those training for selection, low carb isn’t the way to go for high performance.
I see improved performance, leaner body composition and increased motivation from military athletes on high-carb diets. I repeat – increased performance and leaner body composition – just from eating carbs. High-carb diets are, hands down, the way to go for military athletes training for performance. Oftentimes athletes are looking for the next best thing and once someone with a six pack endorses a training method or nutrition protocol online it becomes the next best thing.
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It’s important to note, not all military athletes should start with performance as the primary goal. If an athlete shows signs of over-stress, metabolic syndrome, low libido, excess body fat, interrupted sleep and suppressed appetite, they may need to spend several months on a program to improve their overall health and biomarkers BEFORE focusing on performance.
This is why it’s SO extremely valuable to train under the watchful eye of an experienced coach, who can steer you in the right direction. Choosing the wrong focus and nutrition for your training can severely hamper the speed at which you can increase your performance. Choosing the right focus, nutrition and training plan will dramatically increase both your long-term athletic development and your performance during selection.
 Asker Jeukendrop (2014) A Step Towards Personalized Sports Nutrition: Carbohydrate Intake During Exercise.Journal of Sports Medicine, 44, pg 25-33.