The ABC’s of Carb Periodisation

Jillian Mooney
October 12, 2019

Jill here – low-carb, high-carb, simple carb, complex carb and now carb periodisation!

I suspect it drives you crazy because you just want to eat the right kind of carb to train, recover and perform. But I bet you also want to eat just enough of the right kind carb so that your body is forced to break down and utilise some of your fat stores as energy – right?

Let’s face it, you want it all – productive and progressive training, excellent recovery plus a healthy decrease in body fat all resulting in a power to weight ratio that rocks!

So let’s talk carb periodisation. This blog will focus on the basics – the what, why & how to get started. It’s a huge topic so forgive the slightly longer read.

First a bullet point review so we’re all starting from the same knowledge base:

the function of carb is to provide a source of energy. It is the only macronutrient that is not used as a building block for cells or tissues. Protein and fat are.

If carb is available the body will prioritise it’s use first because the metabolic pathways that turn it into energy (ATP) are quick and efficient

extra carb will be stored first as glycogen in the muscles and then as fat

the body has limited places to store glycogen but unlimited places to store fat

in the right environment the body can be encouraged to utilise more fat to produce energy. Play it right and you have an unlimited energy supply sitting under your skin.

fat provides 9 cals per gram v carb at 4 cals per gram so utilising fat makes sense

the body makes moment by moment ‘decisions’ on what combination of fuel substrate to use depending on internal and external training conditions

fat utilisation is most effective in the presence of some carb, doesn’t have to be a lot

What is carb periodisation?

It is a targeted carb intake that aligns with your training goals of the day.

Do you know your daily training goals? Build aerobic base and mileage? Increase aerobic threshold? Work on sustainable power?, etc.

It’s relatively easy to fuel those goals with standard bottle mix and bars, just fuel consistently and you’ll get through. It’s when you add the goal of increasing fat utilisation to decrease body fat % that carb periodisation becomes a valuable tool.

So said another way, carb periodisation is a strategic manipulation of carb intake per session that balances all goals – training and fat utilisation.

Why is it such a valuable tool?

It’s a valuable tool because we know under what conditions the body will predominantly use carb or fat for energy production. We also know something about the limits to which we can manipulate that ratio.

For example, we know that the body prefers to produce energy from carb when heart rates are high and when oxygen is low. So think turbo sessions, interval training, or if your heart rate is drifting towards z3 on a longer ride. You’ll need MEDIUM or HIGH available carb during these sessions to maximise your training and set you up for a good recovery.

Keto or low carb folks will inevitably ask -but if I restrict carbs during these workouts can I train my body to utilise more fat?

Yes, you can…but only slightly…only as much as your chemistry allows.

You see under intense conditions the rate of energy production from fat utilisation pathways simply cannot keep up with the work demand for very long. You keep going down this route and all you will do is limit your training, recovery and adaptation. Over time you’ll also start to compromise your immune system and a whole host of other systems.

On the other hand, we know that a lower heart rate (z1-2) along with higher oxygen availability lends itself to the metabolic pathways that can comfortably utilise fat for energy production. Restricting carbs during these workouts makes complete sense. A LOW carb environment matched with these conditions will force your body to upregulate fat utilisation pathways to create energy without limiting your training. Bingo!

Higher carbs for more intense workouts and lower carbs for longer, lower rides.

Makes sense doesn’t it?

How to get started?

So we now know it’s about strategically aligning carb intake with all training goals but don’t get conned into thinking that’s an easy balance to strike.

There are few if any guidelines out there for what constitutes LOW, MEDIUM or HIGH carb intakes during training.

That’s because it’s so very individual. It depends on things like target heart rates, muscle mass, current metabolic pathway efficiencies, quality of off-bike nutrition…yada…yada.

That being said, you have to start somewhere so this is how I’d recommend you start:

start by noticing your calorie burn on each training session (yes, you need a Garmin for that). It’s not exact by any means but it’s a good place to start.

rough rule of thumb, a z1to lower z3 session can usually be sustained with 50% calories coming from food leaving 50% calories coming from a mix of glycogen and fat. Where are you currently in relation to that rough rule?

calculate how many grams of carbs you ingest during each session (1g = 4 cals) by looking at labels

calculate how many grams of fat (1g = 9 cals) and protein (1g=4 cals) you ingest

note how you felt in the session – strong? faded at the end? poor recovery?

experiment with different carb amounts. If you go lower on z1-2 rides do you still feel good? If you faded in your more intense sessions maybe increase your carb amount?

10 – 20g carb/hour is enough to add or subtract to your training when you’re working out your LOW, MEDIUM or HIGH ranges, especially if you are focused on body fat loss

You must now start to connect your dots…..heart rate, type of training session, carb grams, quality of training/recovery and decrease in body fat over time. I guarantee you’ll see a pattern emerge and from that pattern you will be able to determine the LOW, MEDIUM and HIGH ranges that align with your training goals.

Once you’ve got these, you’re on your way to on-bike, training specific, carb periodisation.

There’s lots of variation of how to use carb periodisation by the way, especially if you’re doing 2 training sessions per day or if you like your fasted morning rides but that’s another blog.

It’s way more effective if you combine it with off-bike nutrition too. There’s no point in periodising your training only to come home and eat cake and ice cream!

For some, It makes sense to periodise your whole day or the 6 hr block that includes your pre and post-training, e.g., a z1-2 training day = a low carb day or a low carb 6 hr block. That sounds complicated but it’s really not. Again… another blog.

I’ll finish by saying that when I work one-on-one with folks it’s surprising how quickly we can determine relatively accurate carb ranges which get more targeted week over week and month over month.

The key to how quickly we get there is YOU because you are the only one that can balance that subjective feeling of being strong and motivated throughout your training with good recovery and steady body fat loss.

I’ll leave it there but more than happy to continue the conversation so leave your comments/questions and let’s get this carb party started.

If you’re interested in learning more about how to make carb periodisation of any aspect of nutrition work for you drop me a line at or check out our performance coaching section. Both Joe and I are available for one-on-one coaching.