On a long ride your overall goals should be to maintain fluid and energy balance on a day-to-day basis.

by Susan I. Barr, Ph.D., RDN and John Hughes

Susan Barr, is a Professor of Nutrition, University of British Columbia. She is a veteran of the Rocky Mountain 1200, Paris-Brest-Paris, Team Furnace Creek 508, Pacific Crest and PAC Tours. John Hughes is a former director of the WUCA, has been certified by the NSCA as a personal trainer and by USA Cycling as a coach. Learn about Hughes’ coaching at www.coach-hughes.com.


On a long ride such as a double century, brevet, 24-hour race or Paris-Brest-Paris your overall goals should be to maintain fluid and energy balance on a day-to-day basis. We are assuming that you aren’t doing the event as part of a crash weight-loss program! Although it’s possible to ride during a chronic energy shortage, it’s not recommended (nor much fun). In endurance riding, available fuel (not training) limits our pace. Studies with the Tour-de-France cyclists suggest that racers who maintained their weight over the race were more likely to be able to complete the tour and to ride well. For the cyclists studied, that required an average intake of about 6,000 Calories per day. In this article we’ll discuss developing a fuel replacement plan that balances energy requirements and fuel supplies. In the next issue, Lulu Weschler will discuss balancing fluid and sodium needs.

Estimating Energy Needs

Calorie needs while riding vary in proportion to your body weight, the terrain you’re riding through, the road surface, the weight of your bike and type of tires you use, and wind resistance (which includes how much time you spend on someone else’s wheel and whether you’re using aero bars or not) and how fast you’re cycling.

The most accurate way to estimate energy expenditure would be to have an individually calibrated regression of heart rate versus oxygen consumption determined in an exercise physiology lab. Even that can be misleading, though, since during long rides, heart rate typically drifts upward even when energy expenditure isn’t changing. (For example, you start a long ride at a heart rate of 125, and ride at the same pace for three hours, by which time your heart rate might be 135. This would suggest that you were burning more Calories according to the relationship between heart rate and oxygen consumption, when in fact you’re not.)

Approximate Calorie Needs While Riding
Speed (mph)
12 5.6
13 6.2
14 6.8
15 7.4
16 8.1
17 8.9
18 9.8
19 10.7
20 11.8
21 12.9
23 15.5
*Weight in kg = Weight in lbs/2.2

A lab test costs several hundred dollars. If you’d rather spend the money on cookies and bananas, you can “guesstimate” your energy needs while cycling by using the chart on the left, which shows Calories needed per kilogram body weight per hour while riding at different speeds. Obviously, if you’re riding downhill with a tailwind or laboring up a pass at eight miles per hour, the estimates will be wrong. But they’re a reasonable place to start. As an example, a 70 kg cyclist who averages 145 mph (including stops) for a 14 hour double century would need 6,664 Calories (6.8 Calories/kg/hr x 70 kg x 14 hrs), or about 500 Calories / hour.

To the above estimate, add energy needed for the rest of the day. We’ll assume that before and after the ride you’re mainly eating, sleeping, or relaxing. Accordingly, an estimate for this part of the day is about 1 Calorie/kg/hr. Our 70 kg cyclist would be off the bike for 10 hours, so energy needs would be 700 Calories (1 Calorie/kg/hr x 70 kg x 10 hr). The daily total is thus 7,364 Calories (700 + 6,664), or since it’s a guesstimate, about 7-8,000 Calories. That’s a lot of food! The same cyclist, if riding for a full 24 hours, would burn 11,424 Calories (6.8 Calories/kg/hr x 70 kg x 24 hrs).

Sources of Energy

During a ride, the source(s) of energy will vary, depending on the intensity of the ride. At moderate intensities fat contributes a significant fraction of the energy. As the intensity increases, carbohydrate provides more energy. At exercise intensities below the lactate threshold (LT), fat and carbohydrates provide approximately equal amounts of energy, and above LT the major energy source is carbohydrate. If you do a lab test to determine total energy needs at different heart rates, the lab can also tell you what fraction is coming from carbohydrate and what fraction from fat at different heart rates.

An important criterion is where LT falls for a given individual. For many people it’s at 60-70% max, but can range up to over 80% of VO2 max for very fit individuals. Astrand’s Textbook of Work Physiology:

Approximate Sources of Energy While Riding
% of VO2 max CHO/Fat
20-50% about 50/50
60% about 60/40
70% about 70/30
80% about 80/20
90% 90-100% CHO.

A second consideration is what you’re eating. Particularly during very long rides (e.g., Paris-Brest-Paris), your body will use whatever you’re feeding it. So if you’re eating 70% carbohydrate, 20% fat and 10% protein, that’s what you’ll use, while if you’re eating 50% carbohydrate, 40% fat, and 10% protein, that will be your fuel mix. The fat used for energy can be either fat in the diet or body fat. Some riders conclude that they can eat less than they are actually burning, making up the deficit from the midriff. While this will lead to weight loss, it may affect performance in the event. It’s better to diet during training and to make sure that the fuel tank is kept full during an event.

A particular risk in under-eating is that you won’t consume enough carbohydrate. Metabolizing fat for energy requires some carbohydrate; the saying is that “fat burns in the flame of carbohydrate.” Further, the brain can only metabolize glycogen (from carbohydrate) for energy. When you run out of glucose (i.e., deplete your glycogen stores), your eyes cross and your brainturns to mush – you’ve bonked! When you deplete glycogen stores, the body will metabolize protein to provide glucose through a process knows as neoglycogenesis. After months of training your quads, you’ll ride better if you don’t eat them!

Thus, the optimal situation would be for energy intake to match expenditure over a 24-hour period. In events other than RAAM and its relations, that leaves time off the bike to make up energy deficits that may occur on the bike.

Eating During an Event

You’ve estimated your energy needs for 24 hours, including the event. You have four opportunities to take on fuel, and you need a plan so that Calories in = Calories out. Before a long brevet or randonnée, John develops a spreadsheet detailing how much he’ll consume at each of these times:

  • Before the ride / after getting up from a sleep break
  • On the bike
  • At rest stops
  • After the ride / before a sleep break

Eating a large breakfast is a good way to get a head start on your energy and fluid needs for the day. John tries to eat at least 1,000 Calories before a brevet, including a generous amount of carbohydrate. Because you’ll start to ride almost immediately after you eat, choose foods you know will sit well when you start riding. Many riders find that adding some protein helps sustain them for a longer period of time.

On the bike we recommend eating a minimum of 300 Calories every hour, primarily from carbohydrate. This is the minimum for most riders to keep from bonking. For example, 24 oz. of Gatorade contains 150 Calories (and helps meet your hydration needs) and a granola bar will provide another 150 Calories. The rest of your hourly energy needs can be made up at rest stops. If you are doing a RAAM-style event with a crew and want to minimize time off the bike, then you can consume more per hour on the bike.

“On the bike we recommend eating a minimum of 300 Calories every hour, primarily from carbohydrate.”

Some riders have trouble consuming more than 350-400 Calories / hour while riding. There is not a fixed physiological limit to how much you can digest per hour; rather, it relates to how hard you are riding. At high intensities, most of the blood supply is going to the working muscles (to transport oxygen and energy) and to the skin (for cooling). Little blood is available to move energy sources from the digestive system. Thus, you may need to be tactical in your eating. Eat less on a long climb, eat at the top, and digest on the descent. Or, after a big meal at a rest stop, ride at “digestive pace” until you’ve processed the food. If, on long rides, you are chronically unable to eat enough to meet energy requirements, then your pace is outstripping your fuel supply and you should slow down to a pace where you can eat enough.

Finally, when you get off the bike, either at the end of an event or before a sleep break, is a great time to take in more Calories. You may have read that eating immediately after exercise is important for glycogen restoration. The most recent research indicates that when you’ve got eight hours or more until the next day’s ride, chowing down immediately after racking your bike isn’t critical, provided enough carbohydrate is consumed over 24 hours.

However, if you are just taking a short sleep break, this is an excellent time to eat about 1,000 Calories, primarily of carbohydrate, since this is the only recovery time you’ll have before getting back on the bike. Some research indicates that including some protein in the diet will increase the replacement of glycogen.

Real food?

Scientific studies generally indicate that plain food, bought in grocery stores, is as effective at meeting energy needs as special sports drinks and bars. The number one criterion is personal preference. Some people find it easier to drink their Calories on the bike, meeting fluid and energy needs concurrently. Others prefer to drink water and eat food.

A consideration is always “What will be available?”. If you’re on an unsupported ride, you may not be able to carry large quantities of sophisticated liquid food, gels or bars with you. Knowing what you can buy and eat at a mini-mart is a good idea.

Cost is also a consideration for some of us. At $1-$2 per energy bar, the cost of long rides can add up quickly.

The bottom line is that if you like it and eat it (or drink it), it will help.

We are each unique in our requirements and tastes. As you build up to long rides, estimate your personal energy requirements and figure out a personal plan for nutrition. Part of what’s great about this sport is it gives each of us an opportunity to eat a lot and to experiment with what works for us. Bon appetit!