How to fuel a long ride

The short answer

Carbohydrate during a ride helps more the longer the ride lasts. A common guide is about 30 g an hour for rides of 1 to 2 hours, up to about 60 g an hour for 2 to 3 hours, and up to about 90 g an hour for rides over about 2.5 hours, from a mix of glucose and fructose. Your gut adapts to practice, so build up to the higher amounts on your long training rides before you use them in an event.

What the research shows

A systematic review gathered 61 studies that compared carbohydrate with a water-only placebo during exercise. 82% of them found a performance benefit, and the benefit grew as the exercise got longer (Stellingwerff and Cox 2014).

The reason changes with the length of the ride. In efforts of about an hour, the review describes the benefit as coming from the mouth, where carbohydrate signals reward centers in the brain, and the amount barely matters. In efforts over 2 hours, the muscles' own carbohydrate stores run low, and the benefit comes from delivering carbohydrate fast enough for the muscles to burn it.

How much, by length of ride

A 2014 review sets amounts by the length of the exercise (Jeukendrup 2014):

• About 1 hour: a small amount, or even a mouth rinse, can help.
• 1 to 2 hours: about 30 g an hour, from the paper's figure.
• 2 to 3 hours: up to about 60 g an hour.
• Over about 2.5 hours: up to about 90 g an hour, from a mix of sugars.

The same review notes that the amounts can come down when the effort is easy, since your muscles burn less carbohydrate at a low intensity. A relaxed 2 hour ride needs less than a 2 hour race. The review sets these amounts without adjusting for body weight or training level.

On a long day the totals add up quickly. A 4 hour ride at 80 g an hour is 320 g of carbohydrate, which is far easier to take in as small amounts every 15 to 20 minutes than as a few large ones. The regular timing comes from coaching practice.

The research behind the idea that carbohydrate helps in long events is strong. The exact grams per hour for each length of ride rest on fewer studies, so treat them as a starting range to adjust for yourself.

Why the mix of sugars matters

Your gut absorbs a single sugar, such as glucose, at a limited rate, and the body can burn up to about 60 g an hour from 1 source. Above that, the extra tends to sit in your gut rather than reach your muscles. Fructose is absorbed by a different route, so a mix of glucose and fructose lets you take in and use more (Jeukendrup 2014). Above 60 g an hour, check that what you eat and drink carries both.

The review says the carbohydrate can come as a drink or as food, so choose what sits well with you and is easy to eat on the bike.

Training your gut

The gut adapts to what you ask of it. In 1 trial, cyclists who trained for 28 days with plenty of carbohydrate burned more of the carbohydrate they drank during a 100 minute ride, 63.6 g against 54.6 g before (Cox 2010). Their performance improved by the same amount as the group that trained with less carbohydrate, so the trial showed a change in how much the body could use, without a separate gain in performance.

In runners, 2 weeks of practice taking in carbohydrate during exercise cut stomach symptoms about 60% and improved a 1 hour distance test, compared with a placebo (Costa 2017). A review of this work concludes that stomach emptying and comfort respond to practice, and that a high-carbohydrate diet raises how much carbohydrate the gut can absorb (Jeukendrup 2017). The trials are small, so the evidence is promising rather than settled.

Stomach trouble in races also tracks the person. In 221 endurance athletes, those who had stomach trouble in races tended to have a history of it. In Ironman races, higher carbohydrate intake went with more nausea and with faster finishing times (Pfeiffer 2012). That study observed athletes rather than testing an intake, so it shows an association rather than a cause.

A practical way to build up

One way to build up, from coaching practice, is in small steps on your long rides:

• Start at about 60 g an hour on your long rides, or lower if that is new to you.
• Add about 10 g an hour on the next long ride when your stomach handled the last one well, up to about 90 g an hour for rides over about 2.5 hours, or about 60 g for shorter ones.
• Hold the amount after a ride with stomach trouble, and step back if it happens twice.
• Start eating early in the ride, a common coaching habit.
• On race day, use the highest amount you practiced with no trouble.

The 10 g step comes from coaching practice rather than a trial. These are general ranges for healthy adults, and the right amount for you depends on what your gut tolerates (Stellingwerff and Cox 2014). If you manage diabetes, a gut condition, or another medical need, set your amounts with your doctor or a sports dietitian. This article leaves out fluid amounts, sodium, and caffeine, which are topics of their own.

Strength work around long rides

Strength for Cyclists places your leg days around your key rides. The day before a hard or long ride, split squats and other lowering-heavy lifts come off, so you start the long ride on fresher legs. The research behind the plan, and how it handles a race, is on the plans page.