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Carbs and carb loading.

Carbohydrates. A dirty word to some. A delectable one to others. I fall into the ‘others’ category. Blummin’ love carbs. My desert island delicacy…probably in the form of bread. Am literally salivating at the thought of being stuck on an island with nothing but BREAD. Someone shipwreck me NOW…

What are carbs?

Carbohydrates are a source of energy. When eaten, the body converts most carbohydrates into glucose (sugar), which is used to fuel cells such as those of the brain and muscles.

Different types of carbohydrate: sugar, starch and fibre:

Carbohydrate-containing foods generally have a combination of two types of carbohydrates: simple and complex.

  • Simple carbohydrates: They’re also known as sugar. This carbohydrate is made of one sugar or two sugar building blocks connected in a chain. The building blocks can be glucose, fructose and galactose. Because the chains are short, they’re easy to break down, which is why they taste sweet when they hit your tongue (sweets, honey, jams, fruits etc).

  • Complex carbohydrates: Complex carbs can be either starch or fiber. This carbohydrate is made of three or more sugars connected in a chain. They use the same sugar building blocks as simple carbs, but the chains are longer and take more time to break down, which is why they don’t taste as sweet. Foods high in complex carbohydrates include bread, rice, pasta, beans, whole grains and vegetables.

Why do we need carbs?

Carbohydrates are considered to be essential, and they’re found in almost all foods. To perform basic functions, our bodies need carbs, particularly glucose since it’s the preferred fuel for tissues and organs. In fact, glucose is the only source of fuel for our red blood cells. Without enough carbohydrates, the body will break down either hard-earned protein from muscles and organs to create usable glucose for these tissues and organs. Or it’ll break down stored fat to convert it into energy. This process causes a buildup of ketones in the blood, resulting in ketosis. Ketosis as a result of a low carbohydrate diet can be accompanied by headaches, weakness, nausea, dehydration, dizziness and irritability particularly in the short term.

How many carbs a day do I need?

The RDA for carbohydrates is 130 grams per day. This is the minimum amount required to fuel an adult’s brain, red blood cells and central nervous system optimally. If however you have an absolutely HELLISH hill training session with Will scheduled into your day, as I do, then I would times that by about 4 million, billion (possibly even trillion).

(Please don’t anyone be a total donut and take that literally).

Don’t protein and fat provide energy?

While carbs, fat and protein are all sources of energy in the diet, the amount of energy that each one provides varies:

  • carbohydrate provides: about 4kcal (17kJ) per gram

  • protein provides: 4kcal (17kJ) per gram

  • fat provides: 9kcal (37kJ) per gram

In the absence of carbohydrates in the diet, your body will convert protein (or other non-carbohydrate substances) into glucose, so it's not just carbs that can raise your blood sugar and insulin levels.

If you consume more calories than you burn from whatever source, carbs, protein or fat, you will gain weight. So cutting out carbs or fat does not necessarily mean cutting out calories if you are replacing them with other foods containing the same amount of calories.

What’s the role of carbs in exercise?

So we’ve established that carbohydrates, fat and protein all provide energy, but exercising muscles rely on carbohydrates as their main source of fuel. However, muscles have limited carb stores (glycogen) and they need to be topped up regularly to keep your energy up. A diet low in carbs can lead to a lack of energy during exercise, early fatigue and delayed recovery. Fat and protein are harder to turn into energy than carbs, which means you may feel low on energy during your exercise session.

Eating a higher-carbohydrate diet is beneficial to performance for daily exercise in moderate to vigorous aerobic activity (think running, swimming, biking). Why? Because the more carbs you eat, the more glucose you allow your body to store in the form of muscle glycogen. The more glycogen you store, the more fuel you have available for your next burst of exercise.

Carb loading, what is it?

This is used to describe a period of high carbohydrate eating to maximise the body's glycogen stores in preparation for an endurance event. The science and practice in this area has shifted a lot in recent years. Previously a 'classic' approach involved training hard to deplete the body's glycogen, followed by a seven-day, high carbohydrate diet to replenish stores.

It is now believed that carbohydrate stores can be maximised over the two days before a race. This is achieved with high carbohydrate intakes - a rough guide equates to approximately 10g carbohydrate per kilogram of bodyweight - so for example, a runner weighing 60kg would aim to consume 600g of carbohydrate each day.

Experienced runners, who are used to the classic seven-day carb-load, or who find it difficult to eat regularly, may wish to begin three days before the race. There is no need to follow the seven day approach - it may even increase fat stores in some runners.

What should my portion size of carbs be at each meal?

With each meal, try to aim to fill your plate half full with carbohydrate. Protein is less of a focus at the carb-loading stage, but still important for muscle tissue repair, so fill quarter of your plate with protein.

Practical guidelines:

- Make sure you start exercise with sufficient muscle glycogen

- Sufficient means high stores but these stores don’t need to be extremely high.

- For trained individuals this can be achieved by eating carbohydrate rich for 2 days prior to a race, whilst reducing glycogen use (reducing training)

- Because training is reduced and therefore energy expenditure is reduced, a higher carbohydrate intake should not be the result of just eating more. It should be the result of emphasising carbohydrate sources and reducing fat intake. Very often carb loading and overeating seem to be confused by athletes

- There are many different ways to achieve high glycogen stores. The type of carbohydrate seems to have little or no effect, both solid and liquid carbohydrate sources seem to have the same effects

- A carbohydrate intake of 5-7 g/kg per day seems to be sufficient in the majority of cases (with low energy expenditure)

And at this point my carb loading epiphany happens. The boxes I can tick are:

1. Eat a carbohydrate rich diet

2. Reduce training.

The only bit I’m missing is the ‘endurance event’ at the end.

Damn it.

References and quotations:

BBC Good Food.


I am not a dietician or a nutritionist, and make no claims to the contrary. What is written on this site should not be taken as fact or advice. It is merely an opinion blog.

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