What Endurance Athletes Eat When Training Goes Beyond 90 Minutes

Somewhere around the 90-minute mark, stored muscle glycogen stops being enough on its own, and everything an athlete eats from that point forward is working against a deficit that is already growing. That threshold is why fueling advice written for a 40-minute run is useless for a 3-hour one.

The Glycogen Timeline

Muscle glycogen supports roughly 90 to 120 minutes of continuous moderate to hard effort. Depletion is progressive. Stores begin falling off noticeably between 60 and 90 minutes at intensities in the 60% to 80% range of maximum oxygen uptake, and by the 90 to 120 minute mark they can be close to exhausted. What happens next is a change of fuel. The body shifts toward blood glucose and fat, both of which release energy more slowly than glycogen, which is why the wall arrives as a sudden loss of pace and mental sharpness. Everything eaten during a long session is aimed at delaying or preventing that transition.

Intake Targets by Duration

The standing recommendation for sessions past 90 minutes is 60 to 90 grams of carbohydrate per hour. Marathon data supports it directly. Runners who met the 60 to 90 gram range during competition were more likely to finish inside 180 minutes than those who did not.

Higher intakes have been tested. In a mountain marathon, athletes taking 120 grams per hour finished with a lower internal exercise load and lower markers of muscle damage 24 hours later than athletes taking less. A separate 2022 trial found no performance advantage for 120 grams per hour over 90, with the extra oxidation coming at the expense of fat oxidation instead of adding to the total.

The two findings point to a middle setting. Around 90 grams an hour is where most athletes should aim for sessions of two hours or more, and going higher is a recovery decision as much as a performance one.

Glucose and Fructose Transport Limits

The reason the ceiling exists at all is in the gut wall. Glucose crosses the intestinal lining through SGLT1 transporters, which saturate at roughly 60 grams an hour. Fructose uses a separate route through GLUT5, and because the two do not compete, combining them raises the total the body can absorb.

A 2:1 glucose to fructose ratio raises carbohydrate oxidation by around 50% compared with glucose alone and supports intakes up to 90 grams per hour. For athletes targeting 120, a 1:0.8 ratio is the formulation that has been studied. Any product claiming a high hourly delivery is built on that transport ceiling, and checking the sugar sources on the label is the fastest way to tell a serious formulation from a sweet one.

Format Choices at Race Pace

Format decides how much of the target actually gets consumed, since a plan that requires chewing solid food at threshold pace does not survive contact with the session. Drinks deliver carbohydrate and fluid together and suit steady efforts, which is one reason many runners who dislike taking gels during a race still hit their targets. Gels are dense and fast, with a typical unit supplying around 25 grams. Chewable formats fall between the two.

In long-course racing, energy gummies have become standard for that reason. A pouch can be taken a few pieces at a time across 20 minutes instead of all at once, which spreads the load on the stomach and gives the athlete something to do with their mouth other than swallow syrup. The one thing to check before a long session is the carbohydrate per piece, because reaching 90 grams an hour from small units means a lot of them.

Gut Training

The absorption ceiling is not fixed. Repeated exposure to carbohydrate during training increases expression of the intestinal transport proteins themselves, so an athlete who practices eating at 90 grams an hour tolerates it far better after several weeks than on the first attempt.

That makes fueling a trainable skill, and it explains most of the gastrointestinal distress people report in long events. Athletes who train fasted or under-fuel every session, then attempt a high intake on race day, are asking an untrained system to do something new under maximum stress. The fix is to rehearse the exact products and timing during long training sessions, which is also when an athlete finds out which items cause stomach problems for them specifically.

Sodium and Fluid Alongside the Carbohydrate

Carbohydrate needs fluid to move. Concentrated products taken without enough fluid draw water into the intestine and cause the sloshing and nausea that make athletes stop eating altogether, which is the beginning of a bad day. Sodium belongs in the same plan, both because it is lost in sweat and because it supports fluid retention. Most athletes settle on a rotation of a carbohydrate drink for the background intake and a solid or chewable product on a timer for the top-ups.

Real Food at Long Durations

Manufactured products are convenient and they are not required. Plenty of athletes use candy to fuel long sessions, which works for the same reason gels do and costs a fraction as much. Controlled work found potato ingestion as effective as carbohydrate gels for supporting prolonged cycling performance, and the potato group tolerated it as well as the gel group.

Bananas, rice cakes with jam, salted boiled potatoes and dried fruit all deliver carbohydrate at useful rates, and ultra-distance athletes lean on them heavily once palate fatigue sets in after four or five hours of sweet gels. The catch is that real food is slower to eat and harder to time, which is why most athletes use it in the early hours and switch to concentrated formats when the effort intensifies.

Timing Inside the Hour

Hourly targets are useful for planning and useless for execution, because nobody eats 90 grams in one sitting at pace. The workable pattern is a dose every 15 to 20 minutes, which turns 90 grams an hour into roughly 25 grams every 20 minutes or 20 grams every 15.

Starting early matters more than most athletes expect, and the foods to eat in the hours beforehand set the level the in-session intake is topping up. Carbohydrate taken in the first 30 minutes of a long session arrives in circulation while glycogen is still high, which slows the rate of depletion instead of trying to reverse it later.

Athletes who wait until they feel low are eating to recover ground that is already lost, and the gut is less cooperative at that point because blood flow to the digestive tract has already dropped.

The Number to Take Into Your Next Long Session

For anything past 90 minutes, plan on 60 grams in the opening hour and 90 grams in every hour after that, from a mixed glucose and fructose source, with fluid alongside every dose and sodium in at least one of them. Write the timing on your hand or set the watch, because the athletes who hit the target are the ones eating to a clock, and anyone waiting for a hunger signal is already behind when it arrives.

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