On the Second Nature programme, we recommend you follow a lower carb diet. This is because we know lowering your intake of refined carbs and processed foods will have a positive impact on your weight and overall well being.

However, if you’re someone who’s currently doing large amounts of exercise, this may leave you wondering how you’ll continue to meet your exercise goals with fewer carbs.

This is a common question we get asked and one that we’ll cover in detail in this article. But the short answer is: you might not need all those carbs to fuel your exercise after all.

First, it’s important to familiarise yourself with why we advise consuming a lower-carb diet. We’ve summarised the key points of this below, or feel free to read the whole evidence-based guide on the benefits of this approach here.

Key benefits of a lower-carb diet:

  • All of the leading theories of the development of type-2 diabetes include excessive consumption of refined carbs and sugar intake.
  • Evidence suggests lower-carb diets are the most effective for weight loss both in the short and long term.
  • Research shows that the natural increase in protein and healthy fat of a low-carb diet does not increase your risk of heart disease, but actually reduces your risk.

Evaluate your priorities

It is important to remind yourself of your goals and why you joined Second Nature in the first place.

  • Is it to achieve better overall health?
  • Is it to lose weight?
  • Is it to develop a better relationship with food?
  • Perhaps it is all of the above.

Throughout your transition to a lower carb diet, there’s a possibility that your exercise performance may dip. However, this will only be temporary and will resolve as your body adapts to your new pattern of eating.

It’s important to reflect on the bigger picture and ask yourself whether a temporary dip in your performance is worth it to improve your long term health.

This guide will also provide you with a few tips to try and minimise any impacts on your exercise performance throughout your transition to a lower carb diet.

How does our body create energy?

Our muscles are fuelled during aerobic exercise by the production of something called ATP. ATP is the end result of a complicated biological pathway that involves the combination of either fat + oxygen, or carbohydrate + oxygen.

In higher-intensity exercise (anaerobic) our muscles are fuelled by a process that is low in oxygen and predominantly requires glucose. This does not necessarily mean we need a high-carb diet to provide this, our body can also ‘make’ new glucose in the liver.

Glucose is regarded as the body’s ‘go-to’ fuel, if glucose is present, your body will prioritise glucose over fat. Why? Glucose has been shown to be a more efficient fuel in comparison to fat as it can produce more ATP (energy) per litre of oxygen used.

This seems to support the notion that higher-carb diets are needed for exercise. However, the research indicating this was conducted on participants that were used to higher carbohydrate diets, so you would expect to see these results considering their bodies were conditioned to ‘burn’ glucose.

Would the results have differed if the participants were consuming a lower-carb diet and conditioned to ‘burn’ more fat?

What are the limitations of this?

Your body can only store so much carbohydrate in the form of glycogen. The average person will have a max capacity of roughly 1500-2000kcal in their muscles and liver.

As the general consensus has been that glucose is the best fuel for exercise, nutrition recommendations have been aimed at ensuring that our body’s stores of glycogen do not empty during exercise (hence the use of glucose gels and drinks).

The idea is that as soon as glycogen is depleted, your performance will drop - think ‘hitting the wall’ in a marathon. For many individuals, and in particular high-level athletes, this is a tactic they can apply to their advantage without it doing any harm.

Is this a sensible or necessary approach for everyone?

For individuals living with type 2 diabetes or those trying to lose weight, large intakes of carbohydrates might not be the best option.

A high carbohydrate intake can lead to increased blood sugar levels and can prevent the body from burning excess fat stores, regardless of exercise.

What's the alternative?

Rather than an alternative, think of it as a complementary option. The body has another source of fuel, and one that is in much higher abundance; fat. Even a lean adult male will have around 40,000kcals of fat stores in their body; but without the right conditions, you will not be able to access this reserve without a drop in performance.

As we mentioned earlier, if you're conditioned to burn glucose due to a higher-carb diet, your body will be primed to use that. Then when it comes to a point that there is none left to use, it won't have the necessary capacity to burn fat to support the activity to the same level.

Our body has an amazing capacity to adapt over time. If we train our body to burn fat, alongside glucose (as with a lower-carb diet), when your body has run out of glycogen it can then turn to fat with more ease without having a negative impact on your performance. This is referred to as ‘metabolic flexibility’.

Research on cyclists has shown how the body will burn more fat in the absence of carbohydrates to fuel exercise. There seems to be a dose-response relationship, meaning that you effectively control what your body will burn depending on what you eat. If you have a lower-carb intake, your body will adapt to using more fat to make up for the lack of available glucose.

Does this impact on your performance? In the short-term, yes - your body won't adapt overnight. But, if you give your body time, research - also conducted on cyclists - appears to suggest that our body’s are more than capable of performing to a similar level when we're conditioned to burn fat alongside glucose.

This is all focused on athletes, what about the average person?

Well, let’s take a step back. We’ve discussed that when you consume a lower-carb diet, your body will adapt and burn more fat. And if your goal is to lose weight, then this would be a positive step. More exercise on a lower-carb diet also means that you'll burn more excess fat over time, rather than relying on topping up your glycogen stores.

This comes back to your goals and your current situation. You've joined Second Nature for a reason, and you clearly have a goal in mind. This should be your number one priority at this time, your exercise performance may suffer in the short-term.

What does all of this mean? The key points:

  • Each individual's exercise performance will respond differently to a lower-carb diet. Some may find a lower-carb diet improves exercise performance, while others might not see a major difference
  • It's worth trying a lower-carb diet for the other health benefits (i.e. weight loss, improved metabolic health, improved energy levels) and these outcomes will likely result in improved exercise performance over time

Practical ways to implement the Second Nature guidelines to your exercise routine

How can you actually apply this information to your exercise regime within the Second Nature guidelines? Below we’ve written a list of suggestions and possible solutions depending on your current situation.

Goal - weight-loss

  • Aim to limit your carbohydrate intake to the three servings recommended
  • Experiment with exercising after your carb free meal, this will ‘train’ your body to utilise fat as an energy source
  • Prioritise protein, healthy fats, and vegetables in your recovery meals post activity
  • If you're feeling constantly hungry, aim to increase consumption of protein or healthy fat, this can increase fullness without having a negative impact on your weight loss goal. And stay hydrated!

Goal - weight-maintenance

  • If you're struggling with only eating three carb servings a day, then you can perhaps be more flexible with your carb portions. Try adding an extra portion of high-fibre carbohydrates to your meals on days that you're active.
  • Experiment with exercising after your carb free meal, this will ‘train’ your body to utilise fat as an energy source
  • Prioritise protein, healthy fats, and vegetables in your recovery meals post activity
  • If you're feeling constantly hungry, aim to increase the amount of protein or healthy fat you're eating, which can increase fullness while maintaining your weight. And stay hydrated!

Feeding during exercise

  • The key adaptation your body undertakes with a lower-carb approach is that it has a greater capacity to burn fat alongside glucose. With this adaptation, it reduces the requirement of eating more glucose to fuel your activity.
  • It's likely that for most activities and events, having your three balanced meals during the day should be sufficient to fuel your activity, particularly those lasting less than 90-minutes
  • For endurance events lasting longer than 60-minutes, it's likely you’ll need to take in more food to help support your performance. Dried fruit is a good 'food-first' alternative to gels, and research indicates that it can be as beneficial to performance.
  • We'd also recommend using whole fruit, nuts, no-added sugar nut bars, and homemade energy bars (no-added sugar homemade flapjacks for example)
  • Many brands also now offer energy packs made from natural ingredients rather than isolated glucose, which can provide a much more stable release of energy when whole foods are not logistically possible (a half marathon or marathon for example).
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