The Study That Changed Fuel Science

The 1995 Vist and Maughan study is one of the most cited in sports drink and gel formulation, and one of the most misunderstood. This post talks about what it actually showed, and why it’s still relevant after three decades.

What they asked

In 1994-1995, the key sports drink question was: how much carbohydrate can you put into a drink before it stops helping? Vist and Maughan designed a controlled study to measure gastric emptying rate at different osmolalities and carbohydrate concentrations, at both rest and during exercise, using a double sampling aspiration technique that allowed the stomach contents to be directly sampled.

What they found

The first key finding wasn’t just that osmolality slows gastric emptying—that was already suspected. It was the dose-response relationship: how dramatically emptying slowed as osmolality increased.

At isotonic concentrations, around 280-300 milliosmoles per kilogram, gastric emptying was relatively fast. As osmolality climbed above isotonic—into the range of most commercial energy gels—the emptying rate dropped sharply and nonlinearly. Beyond a certain threshold, the system clamped down hard.

The second key finding was that the type of carbohydrate mattered, independently of osmolality. At similar osmolalities, solutions made with longer-chain carbohydrates emptied faster than those made with simple sugars. This was the first controlled demonstration that the chain length of the carbohydrate impacts gastric emptying during exercise independently, not just through osmolality.

Why this matters for formulation

Before Vist and Maughan, the sports nutrition industry focused primarily on carbohydrate concentration as the key variable. The 1995 study shifted the conversation to osmolality as the mechanistically correct variable.

A product with 60 grams of carbohydrate per 100 milliliters made entirely from glucose will have an osmolality in the region of 3,000 milliosmoles per kilogram or more. The same 60 percent concentration from a low-DE maltodextrin will have an osmolality ten times lower. The carbohydrate concentration is identical. The gastric emptying rate is not.

The exercise part

Vist and Maughan also showed that exercise magnifies the effect of osmolality. Gastric emptying was slower during exercise than at rest for comparable solutions, and the emptying rate was more sensitive to osmolality during exercise. Products that were acceptable at rest became more problematic under race conditions at higher intensities.

Summary

The 1995 study cemented three things that are core to modern sports nutrition formulation. Osmolality is the primary variable governing gastric emptying rate. The relationship between osmolality and emptying is nonlinear and threshold-dependent. And exercise increases the sensitivity to osmolality. Every modern decision about carbohydrate chain length, concentration, and ingredient form in high-carbohydrate endurance fuel stems from that study.

References

Vist GE, Maughan RJ. (1995). The effect of osmolality and carbohydrate content on the rate of gastric emptying of liquids in man. Journal of Physiology. 486(Pt 2), 523–531.

Maughan RJ, Leiper JB, Vist GE. (2004). Gastric emptying and fluid availability after ingestion of glucose and soy protein hydrolysate solutions in man. Experimental Physiology. 89(1), 101–108.

Murray R. (1987). The effects of consuming carbohydrate-electrolyte beverages on gastric emptying and fluid absorption during and following exercise. Sports Medicine. 4(5), 322–351.