Multi-day competition: high-fat or high-carb preparation for performance?

Paper title: ‘Short fat-adaptation diet impact on a consecutive day of interval exercise performance’; Publication: Acta Scientiarum Polonorum Technologia Alimentaria 2021; Issue 20 (1) 47-54; Publication date: January 2021

As all athletes are (or should be!) aware, applying the right nutritional strategy is vital for ensuring athletic performance. Over the past 30+ years, hundreds and hundreds of studies have been carried out showing how best to fuel the body for an athletic event and to promote recovery afterwards. Now, even most recreational athletes have a good understanding of the importance of pre-event carbohydrate, and the role of protein in recovery. What’s far less understood however is how to optimize nutrition for multiday performance where athletic performance is required not just for an isolated event or match, but repeatedly on consecutive days.

Multiday requirements

Most of the studies investigating the influence of diet on performance do not take into consideration that an athlete may need to perform closely spaced, repeated events. During the competition season, races and games can be scheduled multiple times a week or even multiple times within a 24-hour period. This in turn can interfere with the usual timings of carbohydrate/protein intake, the athlete’s preferred ‘carbohydrate loading’ regimen, their hydration status and as a consequence, overall nutritional strategies.

Given the vital role of carbohydrate in performance – including multiday performance – some researchers have proposed that a preparation period in which carbohydrate intake is restricted for a period of time prior to a multi-day event and then reintroduced a couple of days beforehand could improve ‘metabolic flexibility’. The theory is that by increasing the athlete’s ability to oxidize fat for energy, this dietary approach can help increase the proportion of energy derived from fat and offset muscle carbohydrate (glycogen) used in initial bouts of exercise, which then spares the glycogen for improved performance in subsequent exercise bouts (rounds of competition/matches/games etc). But is this actually the case?

The research

To try and find answers, a team of Polish and US researchers have investigated whether a fat-adaptation diet is able to improve high-intensity exercise performance on consecutive days of interval exercise performed to exhaustion [Acta Scientiarum Polonorum Technologia Alimentaria 2021; Issue 20 (1) 47-54]. To do this, nine healthy, male amateur athletes were randomly assigned to consume two diets in a crossover study. These were as follows:

• A fat-adaptation diet - consisting of the first five days of a high-fat diet (2.62 grams per kilo of bodyweight per day (g/kg/day) of carbohydrates and 2.23g/kg/day of fat. Days six and seven of the fat-adaptation diet consisted of 5.42 g/kg/d carbohydrates.
• A balanced carbohydrate diet - consisting of all seven days consuming 5.33g/kg/day of carbohydrate.

On day seven of each diet protocol, all subjects performed a treadmill test comprising of repeated intervals, which terminated only when the athletes reached exhaustion. The exact same treadmill test was then repeated the following day (day eight) to see how each diet had impacted the athletes’ multiday performance. After the first dietary intervention, all the athletes returned to their habitual diets for a week then repeated the diet/testing protocol as above except that this time they switched diets – ie those athletes who had initially followed the fat-adaptation diet switched to the balanced carbohydrate diet and vice versa.

The findings

The main finding was that there was a significant decrease in the total distance run to exhaustion after the fat-adaptation diet compared to the balanced carbohydrate diet. The average distance covered in the first treadmill test on day 7 was 11.30kms with the balanced carb diet and 11.07kms with the fat-adaptation diet. On the second treadmill test (day 8), the athletes averaged 11.12kms on the balanced carb diet but only 10.66kms on the fat-adaptation diet. Another finding was the when consuming the fat-adaptation diet, the athletes’ lactate levels on the second day were markedly lower, suggesting they were unable to derive as much energy for the intense work from muscle glycogen stores.

Practical implications

The fact that the athletes ran significantly further on average over the two days on the balanced carbohydrate diet than on fat adaptation diet suggests that a fat-adaptation diet does NOT enhance multiday performance, and may actually impair it. As the researchers went onto explain: “The study does not support the hypothesis that adaptation to a high-fat diet will improve performance, and it is important to note that long-term high fat diet may be harmful for athletes; athletes training on a high-fat diet and using glycogen depletion techniques will train at lower capacities, therefore they may not prepare adequately for the season.”

Overall, we can conclude that when it comes to multiday competition performance, having adequate muscle glycogen availability (as a result of consuming a carbohydrate-rich diet) easily trumps any potential performance gains from cell (fat burning) adaptations caused by carb restriction in the run up to an event. Athletes undertaking multiday competitions are therefore strongly recommended to ensure their diets are rich in carbohydrate both during the week before and during the course of the competition. For a detailed discussion about importance of consuming adequate carbohydrate to keep muscle stores topped up, how much is needed, when and what types are best, readers are directed to this article, which contains all the answers to ensure maximum performance!