In a previous article ‘Can Fat Really Make You a Better Runner?‘ the term fat adaptation, the process of our bodies becoming better trained to use fat stores for energy, was explained, and the question, does it really benefit or hinder our performance? was answered.

Next, let’s look at how you can enhance your body’s ability to oxidise fat as fuel. To do this a more periodised approach is recommended, and this means tailoring nutrition, particularly carbohydrate intake, to training intensity and load. An important point to remember is this does not mean LCHF (Low carbohydrate, high fat).

Here are 12 tips to help you tailor your nutrition to training intensity and load.

1. Aim to include high carbohydrate choices around high-intensity training sessions and races – this will ensure that you can hit the target paces necessary for your progression.

2. In practice this means thinking about including carbohydrate 24-48 hours prior to your session/race, depending on the distance – so if you are planning on doing a track session on a Tuesday night, then you need to be considering fuelling for this as early as Monday’s evening meal, not the snack prior to training.

3. If you are preparing for a half marathon race on a Sunday, I generally recommend, increasing intakes of carbohydrates on Thursday and Friday and then returning to normal eating on Saturday.

This prevents any discomfort from over consuming the day before, which can contribute towards gut issues; it also ensures that you have full glycogen stores – it takes 24-48 hours for carbohydrate to be turned into glycogen stores.

4. How? The aim is to eat little and often so 3 meals a day with around 1/3 plate being made up of complex carbohydrate plus 2-3 carbohydrate-based snacks such as oatcakes with mashed banana or couple of slices of malt loaf or crumpets with jam/honey.

5. For those where time or food availability is a barrier, you can drink your carbs by having diluted fruit juice or smoothies instead of the additional snacks.

6. When it comes to those runs that are done at a low to moderate intensity, it is possible to avoid carbohydrate before and/or during (if long slow run). This will ensure that you use fat stores to fuel that session.

7. Remember we know the body will already use a higher proportion of fat for fuel at these low to moderate intensities.

By training at these paces in a carbohydrate-depleted state, the body will be even more reliable on this fat as fuel. With time, training in this way means that the body gets better at using a higher percentage of fat as fuel.

8. Practically, this means aiming to do these low-intensity/moderate-intensity runs in a fasted state or avoiding carbs for up to 4 hours prior – so if you are planning on doing this run after work, then aim to have carbohydrate at breakfast but keep lunch and snacks protein and fat based.

Remember this is not about losing weight or changing body composition, this is about allowing the body to adapt its fuel usage.

9. During the session, fluid should be drunk and possibly electrolytes if it is very warm; in longer runs, energy can be taken on in the form of fat or protein – good options include salted peanuts and beef jerky.

10. It is important to stress here that firstly these studies have been done on well-trained athletes so I would not recommend trying this if you are new to endurance sport.

Secondly, even in highly trained athletes, I would recommend NO MORE THAN three fasted or depleted sessions a week in order to prevent any issues with a depressed immune system or increase injury risk.

11. If this is something that you want to try but have never done before, remember it has to be a low to moderate intensity run; start short maybe 30-40 minutes and build up the time running fasted or depleted slowly.

12. Finally, it is important to highlight here that while these “fat adaptation” runs are important, it is equally critical to have some long slow runs where you mimic race day, including what carbohydrate fuel you will be taking. This prevents the down-regulation of carbohydrate oxidation, ensuring that you will be able to tolerate your chosen fuel. 

This is one of the biggest mistakes I have come across with the runners I work with, not practising on race day and then suffering severe gastro-intestinal problems on race day.

About the Author
Renee McGregor is a Performance Dietitian and author who works with elite athletes, coaches and sport science teams to provide nutritional strategies to enhance performance and manage eating disorders.

She is the author of Training Food, Fast Fuel books and Orthorexia, when soon to be released Healthy eating goes bad.