# Longer than two hours: why fat and amino acids belong in a sports drink

> On very long sessions the body burns more than sugar alone. What research shows on MCT fat, BCAA oxidation and L-carnitine - and how WOO® Ultra Endurance Pfirsich puts it into practice.

From the third hour onwards, the question changes. It is no longer just about topping up carbohydrates, but about which other fuels the body draws on - and where it takes them from. Relying on sugar alone leaves part of the bill to your own muscles.

## What the muscle burns in addition after two hours

During short, intense efforts, carbohydrates supply virtually all the energy. The longer the session lasts and the emptier the **glycogen stores** become, the more the metabolism falls back on other sources - including amino acids from the muscle itself.

Leucine, isoleucine and valine are oxidised directly in the muscle, and their oxidation rate rises measurably as soon as carbohydrate availability drops. Their share of total energy stays small. What matters is the origin: the material comes from the working musculature. Drinks containing a little protein have been examined with exactly this in mind: several papers found a longer time to exhaustion and lower creatine kinase values, though the effect shrinks in calorically matched comparisons.

## Fat as a second substrate - and the special role of MCT

Gram for gram, fatty acids deliver more than twice the energy of carbohydrates, but they require more oxygen and more time. Medium-chain triglycerides, or **MCT**, reach the liver directly via the portal vein rather than the lymphatic route, and they cross the mitochondrial membrane without the carnitine transporter.

The research is sober: large amounts of MCT during exercise cause gastrointestinal complaints without any performance advantage, while small amounts are well tolerated and do not displace carbohydrate oxidation. That is why the fat content of an endurance drink should stay deliberately low - four grams per bottle, not forty.

Long-chain fatty acids need a transporter to enter the mitochondria: carnitine. Muscle carnitine content, however, can only be raised over weeks and only in combination with carbohydrates - a single serving during exercise fills no store.

## How WOO® Ultra Endurance Pfirsich is set up

The tin holds 1000 grams of powder, that is twenty 50-gram servings. The formula combines three carbohydrate sources - fructose, galactose and D-ribose - coconut fat powder as the fat component, all eight essential amino acids including a BCAA complex of L-leucine, L-isoleucine and L-valine, plus L-carnitine and sea salt. One serving provides 203 kilocalories, 32 grams of carbohydrate, 7.3 grams of protein and 4.1 grams of fat.

For the protein it contains, the authorised statements apply: protein contributes to the maintenance and growth of muscle mass and contributes to the maintenance of normal bones. Use as directed by the manufacturer: dissolve 50 grams in 750 millilitres of water and drink as required - before, during and after efforts lasting more than two hours.

## Frequently asked questions

**Is the drink worth it for a one-hour session too?**
For short efforts a plain carbohydrate solution is enough. The fat and amino acid content targets situations in which glycogen stores genuinely run short - and that only happens from around two hours onwards.

**Does the stomach tolerate fat during exercise?**
In small amounts, yes, particularly as MCT. Four grams per bottle sits well below the quantities at which complaints appeared in studies. As always: test it in training, not on race day.

**Does the drink replace the post-training meal?**
No. It supplies you during the effort. Refilling glycogen stores and taking in protein remain a separate job afterwards.

## Sources

Wagenmakers AJM (1998), Exercise and Sport Sciences Reviews - Muscle amino acid metabolism at rest and during exercise.
Jeukendrup AE & Aldred S (2004), Nutrition - Fat supplementation, health, and endurance performance.
Wall BT et al. (2011), The Journal of Physiology - L-carnitine and carbohydrate ingestion alters muscle fuel metabolism during exercise.
Saunders MJ, Kane MD & Todd MK (2004), Medicine & Science in Sports & Exercise - Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage.

*[WOO® Ultra Endurance Pfirsich](/en/shop/woo-ultra-endurance-peach-can) as a 1000 g tin - available in our shop.*