Every endurance cyclist has been there. One moment you are cruising along, feeling strong and confident. The next, your legs turn to concrete, your brain fogs over, and even the slightest incline feels like a mountain. You have bonked, and there is no quick fix once it happens. The only real solution is to prevent it from happening in the first place.
Bonking, also known as hitting the wall, is the dramatic depletion of glycogen in your muscles and liver. It is one of the most common problems that cyclists face on rides longer than 90 minutes, and it is almost entirely preventable with the right fueling strategy. Here is everything you need to know about keeping your engine running on long rides.
What Exactly Is Bonking?
Your body uses two primary fuel sources during cycling: fat and carbohydrates. Fat is abundant even in the leanest athletes, providing enough stored energy for hours of moderate exercise. Carbohydrates, stored as glycogen in your muscles and liver, are more limited but are the preferred fuel for moderate to high-intensity efforts.
When you ride at intensities above your fat-burning zone, your body increasingly relies on glycogen. The average person stores around 1,500 to 2,000 calories of glycogen, which can be exhausted in roughly 90 minutes to two hours of sustained moderate-to-hard riding. When glycogen runs out, your body is forced to rely almost entirely on fat oxidation, which produces energy too slowly to sustain anything more than a very easy pace.
The result is the bonk: a sudden, dramatic loss of energy, coordination, and mental clarity. Your brain, which relies heavily on glucose, is particularly affected. Riders who have bonked describe it as feeling disoriented, emotional, dizzy, and unable to process simple decisions. It is profoundly unpleasant and can be genuinely dangerous if it happens in traffic or on a technical descent.
Pre-Ride Nutrition: Starting With Full Tanks
Your fueling strategy begins long before you clip into your pedals. What you eat in the hours leading up to a long ride sets the foundation for your energy levels throughout.
The Night Before
Eat a carbohydrate-rich dinner the evening before a long ride to ensure your glycogen stores are topped up. This does not mean stuffing yourself with three plates of pasta. A normal-sized meal with a good portion of rice, pasta, potatoes, or bread, combined with some protein and vegetables, is sufficient. Avoid high-fiber or spicy foods that might cause gastrointestinal distress during the ride.
Morning of the Ride
Eat breakfast two to three hours before your ride to give your body time to digest. Aim for 100 to 150 grams of carbohydrates from easily digestible sources like oatmeal with banana, toast with jam, or rice cakes with honey. Keep fat and fiber moderate to prevent stomach issues on the bike. If you only have an hour before riding, opt for something lighter like a banana, an energy bar, or a sports drink.
Fueling During the Ride
This is where most riders go wrong. The goal is to replace a portion of the carbohydrates you are burning while riding, preventing your glycogen stores from dropping to critically low levels.
When to Start Eating
Begin eating within the first 30 to 45 minutes of your ride, well before you feel hungry. By the time you feel hungry, you are already behind on fueling, and it takes time for your body to absorb and process the food you eat. Think of it as topping up a tank that is slowly draining rather than waiting until the warning light comes on.
How Much to Eat
Current sports nutrition research suggests consuming 60 to 90 grams of carbohydrates per hour during endurance rides. For rides under three hours, 60 grams per hour is usually sufficient. For longer efforts, aim toward the higher end. To absorb more than 60 grams per hour, you need to use a combination of glucose and fructose sources, as your gut can only absorb roughly 60 grams of glucose alone but can handle an additional 30 grams of fructose through a separate transport mechanism.
What to Eat
The best on-bike fuel is whatever sits well in your stomach and is easy to eat while riding. Energy gels are convenient and deliver concentrated carbohydrates quickly. Energy bars provide a more sustained release and are good for the first half of long rides when your digestive system is functioning well. Real food options like bananas, fig bars, rice cakes with jam, dates, and gummy sweets all work excellently.
Sports drinks serve double duty by providing both hydration and carbohydrates. A standard sports drink contains around 30 to 40 grams of carbohydrates per 500 ml bottle. Combining a sports drink with solid food or gels makes it easier to hit your hourly carbohydrate targets without overloading your stomach.
Eating Strategy by Ride Duration
For rides under 90 minutes, water and a pre-ride meal are usually sufficient. You may benefit from a sports drink, but dedicated fueling is not critical for shorter efforts.
For rides of two to three hours, aim for 60 grams of carbohydrates per hour starting from the first 30 minutes. This could be one gel plus a bottle of sports drink per hour, or two energy bars plus water over the course of the ride.
For rides over three hours, increase to 60 to 90 grams per hour and start with solid food in the early hours before switching to gels and liquids as the ride progresses and your stomach becomes less tolerant of solids. Bring more fuel than you think you need, as running out of food three hours into a five-hour ride is a recipe for disaster.
Hydration: The Other Half of the Equation
Dehydration accelerates glycogen depletion and makes bonking more likely. Even a two percent loss of body weight through sweat can measurably impair performance. On a hot day, you can lose over a liter of sweat per hour.
Aim to drink 500 to 750 ml per hour in moderate conditions and up to a liter per hour in hot weather. Set a timer on your bike computer or watch to remind yourself to drink every 15 to 20 minutes. By the time you feel thirsty, you are already significantly dehydrated.
Include electrolytes in your hydration, especially sodium. You lose significant amounts of sodium through sweat, and failing to replace it can lead to hyponatremia if you are drinking large volumes of plain water. Electrolyte tablets or powders added to your bottles are an easy solution.
Training Your Gut
One of the most overlooked aspects of ride nutrition is gut training. Your gastrointestinal system adapts to the demands you place on it, just like your muscles do. If you never practice eating on the bike, your stomach will rebel when you try to consume 90 grams of carbohydrates per hour on race day.
What to Do If You Bonk
Despite your best efforts, bonking can still happen. If it does, stop and eat immediately. Fast-acting sugars like gels, sports drinks, cola, or even candy will raise your blood sugar most quickly. You will not recover fully on the ride, but you can bring your energy levels up enough to get home safely.
Reduce your intensity dramatically. Ride at the easiest pace you can manage while your body processes the fuel. Expect it to take 15 to 30 minutes before you start feeling human again. Do not try to push through a bonk, as your body simply does not have the fuel to sustain higher efforts.
Frequently Asked Questions
Can I train my body to burn more fat and avoid bonking?
Yes, to a degree. Consistent Zone 2 training improves your fat oxidation rate, meaning you burn more fat and spare glycogen at a given intensity. However, even highly fat-adapted athletes still rely on glycogen for efforts above a moderate pace. Fat adaptation complements a fueling strategy but does not replace it for most riding scenarios.
Are energy gels better than real food?
Not necessarily. Gels are convenient and quickly absorbed, which makes them useful during hard efforts or in the later stages of long rides. But real food like bananas, rice cakes, and fig bars work just as well and are often easier on the stomach, especially during the first few hours of riding. Many experienced riders use a combination of both.
How do I know if I am eating enough during a ride?
Track your intake for a few rides to calibrate your intuition. Count the grams of carbohydrates in each item you consume and note the total at the end. If you finish a long ride feeling strong and clearheaded, your fueling was adequate. If you fade badly in the final hour, you likely need to eat more or start eating earlier. Over time, you will develop an instinct for when and how much to eat.
