Road Worlds and Berlin Marathon: Why Endurance Fueling Changes With Exercise Demands

Published in connection with the 2026 UCI Road World Championships, September 20–27, and BMW Berlin Marathon, September 27, 2026

A steady hour of exercise, a long road race, and a marathon create different fueling problems. Muscles need a continuous supply of energy, but the amount and type of fuel they use change with the effort. Food and fluid must also be available, practical to consume, and tolerable while moving.

The 2026 UCI Road World Championships in Montréal, September 20–27, and the BMW Berlin Marathon on September 27 provide two settings for exploring these demands. Cycling and running differ in pacing and logistics, yet both require athletes to connect nutrition planning with the work ahead.^1,2

Exercise Demand Changes the Fuel Mix

Muscle contraction depends on ATP, the molecule cells use to transfer energy for immediate work. Because muscles store only a limited amount of ATP, the body must continually regenerate it. Carbohydrate and fat supply most of the energy for this process during endurance activity, while protein generally makes a smaller contribution.³

The body uses carbohydrate and fat together rather than switching completely from one to the other at a fixed time. Their relative contributions change with intensity, duration, training status, nutritional state, and fuel availability.³

Fat can provide a substantial share of energy at lower and moderate intensities. As relative intensity increases, carbohydrate generally becomes more important in meeting the demand for rapid energy production.³

A cyclist’s climb, attack, or sprint illustrates how quickly demands can change. Marathon running is often more continuous, but pace and terrain still affect the effort required. Large fat stores do not remove the importance of carbohydrate when an athlete needs to sustain demanding exercise intensities.^3,4

Carbohydrate Planning Includes Both Quantity and Tolerance

Some carbohydrate is stored as glycogen, mainly in skeletal muscle and the liver. Muscle glycogen supplies fuel locally, while liver glycogen helps maintain blood glucose. Prolonged or demanding exercise can substantially reduce these finite stores.^3,4

As glycogen availability declines, maintaining a demanding pace can become more difficult. Carbohydrate intake during exercise is therefore relevant in many endurance events, although duration, intensity, starting fuel availability, and performance goals all affect the plan. A short, easy session does not create the same needs as several hours of racing.^4,5,6

For endurance exercise lasting approximately 1–2.5 hours, established guidance commonly recommends 30–60 grams of carbohydrate per hour. For longer efforts, particularly those lasting more than about 2.5 hours, intakes of up to around 90 grams per hour may be appropriate, depending on demands, tolerance, and practicality. These are guidance ranges rather than compulsory targets for every athlete.^5,6

At higher intake rates, carbohydrate type matters too. Combining carbohydrates that use different intestinal transport pathways, such as glucose and fructose, can support greater carbohydrate delivery and use than glucose alone. Tolerance still needs to be established in training.^5,6

Practicing food and fluid intake before or during exercise is sometimes called gut training. A systematic review found that such strategies may reduce gut discomfort and improve some measures of carbohydrate tolerance, but results varied across gastrointestinal outcomes. Practice can help refine a plan; it does not guarantee tolerance of any intake target.⁷

The form of carbohydrate is another practical choice. A carbohydrate-electrolyte drink can supply fluid, carbohydrate, and sodium together when all three are useful. Foods and other sports products may also fit the plan. Sports drinks are not necessary for every short or easy session.^5,9

Hydration Planning Must Account for Losses and Access

Exercise produces heat, and sweat evaporation helps the body lose heat. Sweat losses vary with environmental conditions, intensity, duration, clothing, body size, heat acclimatization, and individual physiology.^8,9

A single hourly drinking target therefore cannot fit everyone. Planning should consider likely losses and opportunities to drink. Estimating sweat losses during training in similar conditions can help inform that plan.^8,9

Both insufficient and excessive intake can cause problems. Substantial dehydration can increase physiological strain and impair performance. Drinking more fluid than the body loses can also be dangerous and contribute to exercise-associated hyponatremia, a low concentration of sodium in the blood during or after exercise. A sodium-containing sports drink does not eliminate this risk when fluid intake is excessive.^8,9

Logistics affect how a plan works. A cyclist may carry bottles and receive supplies while riding. A runner may use aid stations, carried supplies, or both. Intake must fit those opportunities while remaining comfortable at race pace.

A workable hydration plan aims for sufficient intake without overdrinking and can be adjusted when conditions change.^8,9

Recovery Priorities Depend on the Next Effort

After prolonged endurance exercise, recovery may involve replacing fluid losses, replenishing glycogen, and consuming enough protein and total energy to support tissue repair and adaptation. How quickly these priorities need attention depends partly on the time before the next demanding effort.^5,6

An athlete competing again within hours has less time to restore fuel and fluid than someone with several days before the next hard session. The recovery timetable should reflect that difference.^5,6

Ordinary meals, snacks, and drinks can provide carbohydrate, protein, fluid, and electrolytes. Specialized products may offer convenience when appetite, food access, or a short turnaround makes eating more difficult.⁵

The most useful preparation is to connect the race schedule with a plan that has been practiced: what can be consumed, when supplies are available, and what recovery time follows. That makes nutrition a practical part of race preparation rather than a set of numbers first attempted on race day.