Will I Gain Body Fat When Carbohydrate Loading for Races?

I’ll start todays post with a question:

During key races or hard training rides, can you start strong and finish strong with minimal deterioration in performance.

In other words, after 3-4 hours in the saddle, do you still have the legs to sprint to the finish line?

Ultimately, a cyclist’s ability to produce repeated efforts is essential to their success.

Repeatability from a nutrition perspective is largely determined by how much carbohydrate is stored in the muscle and liver in the form of glycogen.

This is often referred to as carbohydrate availability. In this sense, high carbohydrate (CHO) availability supports repeatable efforts and overall performance, where low CHO availability results in the opposite.

Most riders will know when they’re in a state of low CHO availability, as this is otherwise known as bonking, fading or hitting the wall...just a bad place to be.

During medium-high intensity rides, CHO utilisation will be far higher than our ability to consume, absorb and replenish stores. Therefore, the tanks will slowly empty, even with an optimal fuelling strategy and a well-trained gut..

Therefore, to reduce the likeliness of the tanks emptying, we must ensure that each race or hard training ride begins with an ample amount CHO on-board.

If for example, you had a very hard training week, it’s unlikely that your muscle and liver glycogen will be fully topped up and supercompensated going into the weekends big ride or race. Furthermore, if you've been restricting calories to drop body fat and improve body composition, the tanks will be much lower.

A CHO rich breakfast offering foods high in glucose and fructose will certainly help, but perhaps not to the extent you’d hope for. This is because CHO replenishment takes time.

With this in mind, there’s a need to CHO load the day before.

The concept of CHO loading is well understood amongst athletes. However, there’s often hesitation to its full implementation due to a fear of gaining unwanted body fat.

In essence, a CHO load requires the athlete to consume an excess of calories from CHO, where an excess of calories is often linked to an increase in fat storage.

So the question we need to answer is: Will the extra CHO be converted to fat when eaten in excess?

To answer this question, we’re turning the clocks back to a study in 1982 by Acheson and colleagues where they investigated the effect of glycogen and fat storage after they fed participants a very large meal containing 500g CHO with very little protein or fat.

That’s correct, one single 500g CHO meal consumed within a 50 minute period. Well, 479g of CHO from bread, jam and fruit juice to be exact.

Over the 10 hour monitoring period, they found that 133g of CHO, 17g of fat and 29g of protein were oxidised and used for energy, where 346g of the 479g CHO consumed was stored as glycogen.

Ultimately, the losses in fat and protein were greater than what they consumed in the single meal…where glycogen replenishment significantly increased, and as a result, their stores became supercompensated.

These results demonstrate that fat gain does NOT exceed fat burning after one low fat, very high CHO meal. Therefore, there was no net gain in fat mass.

When the intake of dietary fat is minimal, and the intake of CHO is very high, CHO becomes the primary fuel source to support the body’s energy requirements. In doing so, reduces fat utilisation/burning. So, you won’t lose any body fat, but you’re unlikely to gain any either.

So, not a single gram of fat was stored as body fat over the 10 hour period?

The researchers measured the small conversion of 45g of glycogen to 15g of fat over the 10 hour period. But that being said, ~20g of fat was simultaneously being used for energy provision. So, fat storage and burning balanced out (give or take 5g).

To put this into context, an 80kg athlete with 15% body fat will have approximately 92,000kcal of stored energy as body fat. Looking at this ratio, the mere 15-20g flux is very insignificant.

Therefore, when healthy individuals significantly increase the amount of CHO in their diet in absence of dietary fat, the CHO consumed is largely directed to glycogen stores.

Many athletes fail to CHO load properly as they often consume high amount of dietary fats in addition. I.e. pizza, lasagne and spaghetti bologenese with high amounts of cheese is not an effective CHO load strategy. Tomato Pasta, basmati rice, cereal, bread and fruit is.

This isn’t to say that athletes must eliminate fat from their diet when CHO loading, but we would recommended that dietary fat is kept on the lower side so it’s more aligned to the dietary conditions seen in this study.

From a practical standpoint, CHO loads can range anywhere between 8-10g/kg, meaning that an 80kg endurance athlete will consume 640-800g of CHO in the day prior to racing.

Dietary fat is then kept on the lower end of the recommended range at 0.5-0.75g/kg, which is approx. 40-60g for an 80kg athlete.

Dietary fat intake is typically lower than the ~1g/kg recommendation for normal day-day living, but for the infrequent occasion where a large CHO load is needed, this dietary eating pattern is recommended to maximise glycogen storage, increase your chances of winning, and minimising body fat gain in the process.

A win-win-win strategy!

- Coach Chris