10,080–that’s how many minutes are in a week. Maintaining a diet through all those minutes, for weeks or months, requires supreme, almost unwavering willpower.
Even The Rock doesn’t do it; his Sunday night cheat meals are stuff of legend, consisting of thousands of calories of his favorite food.
The social side of dieting is tough. It takes dedication to remain unmoved on a diet; happy hour invites, dinners out, work-sponsored lunches–saying “no” to all these are small wins on the battlefield of dieting. For a diet like the ketogenic diet, avoiding carbohydrates can feel like tip-toeing through a minefield of Western, carb-centric eating.
For athletes, it can be difficult because we rely so heavily on carbohydrates for fuel. Of course, there’s growing research about how to use bodily fat as a fuel source,1 but carbohydrates have been the gold standard exercise nutrition for years.
Carb cycling is planned consumption of different amounts of carbohydrates, usually throughout the week. Everyone can develop their own carb cycle based on need; for example, keto athletes might work in carb days during especially hard training blocks.
While carb cycling isn’t for everyone, it can be a great way to optimize a diet based on your personal needs.
What’s a Carb, Anyway?
There are three different types of macronutrient fuel sources in our food: fats, proteins and carbohydrates
The main function of dietary carbs is to be a source of energy. Some even argue they aren’t essential, and can be made from dietary protein and fat.2 This process is called gluconeogenesis, a metabolic pathway generating glucose from non-carbohydrate substrates.
Carbs (especially refined carbs) raise blood sugar, resulting in the body producing extra insulin to bring that blood sugar down. Insulin is a hormone that triggers fat storage–so more carbs means more insulin which means more conversion of carbs to fat stores.
As a fuel source, carbohydrates replenish glycogen stores in the muscle and liver. They also maintain blood glucose concentrations as fuel for the body, but also for the brain. That’s the spike in energy you experience after an afternoon stack, as blood glucose fluctuates throughout the day when we consume carbs.
Simply put, carbohydrates are the body’s most readily available fuel. But when we don’t use that fuel, carbohydrate manifest as fat.
When following a keto diet, lower carb intake is necessary (like 25g of carbs per day–the amount in a single banana). This encourages the body to burn fat and also to convert fat to ketones. Consuming carbohydrates causes insulin release, which inhibits ketone production in the liver.
Science Behind Carb Cycling
What is carb cycling, and why is it beneficial? Looking at the science can provide some clarity. Maybe a more accurate definition of carb cycling is carb manipulation.
The goal is to match the body’s need for glucose depending on activity or activity level overall.
High-carb days are usually matched with workouts when you might need more glucose–like high-intensity interval sessions or a long day in the weight room.
When you exercise at a high intensity, the body makes most of its energy from carbohydrates, either breaking it down aerobically (with oxygen), or anaerobically (without oxygen), forming lactic acid. This would be the optimal time to introduce a higher amount of carbohydrates into the diet because the body uses more carbohydrate during the workout itself, and then after the workout to make glycogen to refuel and decrease muscle breakdown.3
When looking for your highest possible power or speed output, carbs are often necessary for the body to produce its best results during intense training sessions.
In traditional carb-cycling, low-carb days are meant for days on which you do not train–the idea is the body doesn’t need carbs because its demand for fuel is far less than on workout days.
But further investigation by scientists have shown some of the advantages of training on these low carb days, which has two main benefits: it helps to speed up general adaptations to aerobic training, and it increases fat burning and thus improves endurance.
One of the key, groundbreaking experiments in this field was conducted using single-legged cycling exercise. Athletes had to cycle using just one leg at a time; the left leg cycled one hour straight, and the right leg did two half hours with a few hours in between where no recovery fuel was given. This means that the right leg was training in a carb depleted state during the second session. Muscle biopsy samples revealed that the twice-trained leg saw bigger gains in the enzymes that are key for aerobic respiration. This led to the conclusion that low-carb training could accelerate aerobic gains.4
Strategic low-carb days focus on switching the body back to using fat as energy and increase aerobic capacity. Research is continuing on this topic, but athletes are looking to boost the ability of the body to tap into fat as a fuel source, since we store more fat than carbohydrates.
Training in a low-carb state has been shown to increase the ability of the body to burn fat over the long haul, improving metabolic flexibility.5 There have even been studies noting keto-adapted athletes can use fat in preference to carbohydrates for moderate intensity endurance exercises, in which carbohydrates would usually be used as fuel.6
But it takes time. Robert Sikes is a professional bodybuilder and founder/owner of Keto Savage. He’s a bodybuilder on the keto diet; backstage at events, he receives inquisitive looks from competitors when they find out he’s keto. But the results speak for themselves and after events, he’ll even get asked about he’s able to train with such little carb intake. He says it can takes years to full fat-adapt, and that it’s something that doesn’t happen in the short term.
“You need to allow yourself to be completely adapted to life without carbs. Play the long game. Be diligent with hitting macros and eating wholesome foods.”Robert Sikes
It is becoming widely accepted that athletes should adopt carb cycling or periodization of carbs based on training needs. This ensures fuel for the work required (so training intensity isn’t compromised), while also empowering the body to metabolically trapease between carbohydrates and fats as fuel sources as available.9
This article was originally published on HVMN by Nate Martins