Eating After the Ride Part 2

Posted on May 28, 2011 by Kevin Murnane

A streamlined version of the information presented in this post can be found in Nutrition for Cyclists: Eating and Drinking Before, During and After the Ride which can be purchased on Amazon.com. For information about the book and how it relates to what I’ve posted to Tuned In To Cycling, please check out this post.

A comment on our Eating After the Ride post raised the question of whether the recommendation to consume one half gram of carbohydrate for each pound of body weight during the 30 minutes after you finish a bike ride is contradicted by recommendations to avoid all carbohydrates immediately after exercise because carbs supposedly disrupt a two hour “synergy window” during which the release of human growth hormone (HGH) by the body is claimed to produce a wide range of miraculous effects. The HGH industry is a cesspool of fraud, ignorance, scams and ridiculous claims that are completely unsupported by scientific research (more on this can be found in Human Growth Hormone and Cycling).

One piece of HGH-related nonsense about the so-called “synergy window” that has been copied and reproduced on many, many websites and blogs cites a study published in the Journal of Applied Physiology as evidence in support of its claims. The research that is cited has nothing whatsoever to do with HGH or a two-hour post exercise window but it is relevant to concerns of cyclists who are concerned with what to eat after a ride.

The study was carried out by S.A. Newsom and colleagues. It is titled “Energy deficit after exercise augments lipid mobilization but does not contribute to the exercise-induced increase in insulin sensitivity” and you can read it for yourself here. The investigators were interested in the consequences of replacing the energy stores burned during exercise with either fats or carbohydrates. They carried out a carefully controlled study that involved different groups of experimental subjects engaging in a period of controlled exercise followed by the ingestion of carefully controlled meals and snacks for the rest of the day. The investigators varied whether energy stores were replaced by carbs or fats and measured insulin sensitivity (an indicator of the degree to which the system is primed and ready to process glucose into glycogen) and lipid metabolism (an indicator of the extent to which adipose tissue, i.e., fat, is being mobilized or broken down) the following day.

Here’s what they did.

Nine men between 28 and 30 years of age participated in the study. There were four experimental conditions and each participant took part in each of the four conditions over four different experimental sessions.

The following general procedure was carried out in each of the four experimental sessions:

* Participants fasted over night and were admitted to the hospital where testing would take place the next morning.

* After admission and a 30 minute rest period, oxygen consumption and carbon dioxide production were measured.

* This was followed by approximately 90 minutes of exercise in 3 of the 4 conditions. The 4th condition was a control where participants did not exercise. The exercise was split evenly between a treadmill and an exercise bike and each participant burned approximately 800 kilocalories (kcal) during the exercise period. Oxygen consumption and carbon dioxide production were measured at several points throughout the exercise period to insure participants were exercising at the required rate and expending the required amount of energy.

* The participants ingested meals at periods of 30 minutes, 5 hours, and 10 hours after exercise. The experimental manipulation was in the nutritional make-up of these meals.

* Three hours after the last meal all of the participants ingested an identical snack to control for any effects of the last food eaten.

* The participants then spent the night at the hospital and a variety of physiological measures were taken the following morning.

There were four experimental conditions in the study. These were:

1. A Control condition in which participants did not exercise. Participants were fed meals that maintained their fat and carbohydrate balance.

2. A Balanced condition in which participants were fed enough carbohydrate to replace the glycogen lost during exercise and enough fats to replace the fats lost during exercise.

3. A Low Carbohydrate condition in which participants were fed meals that did not contain enough carbohydrate to replace the glycogen burned during the exercise period. The total energy loss of the exercise (kcal burned from both fats and glycogen stores in the body) was offset by increasing the amount of fat in the meals.

4. A Low Energy condition in which participants were fed enough carbohydrate to replace the glycogen lost during exercise but were not fed enough fat to replace the fat burned during exercise.

There are two important comparisons to consider with regard to the consequences of failing to replace either fats or glycogen (by ingesting carbs) after exercise.

(A) In the Control condition no exercise takes place and energy balance is maintained by replacing energy lost (during rest) to fat metabolism with fat in the diet and energy lost to burning glucose with carbohydrate in the diet. In the Low Carbohydrate condition energy balance is also maintained but it is accomplished by shorting the amount of carbohydrate in the diet and replacing the missing carbohydrates with fats. Testing the next day showed that the amount of glycogen stored in muscle tissue was significantly lower in the Low Carbohydrate condition than in the Control condition. Insulin sensitivity was also higher in the Low Carbohydrate condition than in the Control condition. This means that insulin was more active the following day in the Low Carbohydrate condition. Insulin plays a critical role in converting blood glucose into glycogen that can be stored in the muscles (and liver) and the system would be expected to show higher sensitivity to insulin when it is in glycogen debt and operating to replace lost glycogen stores.

(B) In the Balanced condition exercise take place and energy balance is maintained by replacing energy lost (during exercise) to fat metabolism with fat in the diet and energy lost to burning glucose with carbohydrate in the diet. In the Low Energy condition energy lost to burning glucose is replaced by carbohydrates in the diet (in other words, muscle glycogen lost to exercise is completely replaced) but energy lost to burning fats is not. Testing the next day showed no differences in muscle glycogen between the two groups. However, there was an increase in plasma fatty acid mobilization and oxidation and an increase in plasma triacylglycerol concentration the next day in the Low Energy condition as compared to the Balanced condition. This means that fat metabolism was higher in the Low energy group.

What does this mean for the active cyclist?

The results discussed in (A) above provide another source of evidence that failure to ingest enough carbohydrate following exercise results in lower stores of muscle glycogen the next day. A deficit in muscle glycogen translates into less energy on the bike, lower performance levels, and an increased tendency to bonk on the ride. The critical need to replace muscle glycogen after exercise is the basis for the recommendation made in Eating After the Ride to ingest a heavy carbohydrate load during the first 30 minutes after you get off the bike in order to take advantage of the brief period during which a high-efficiency glycogen storage process take place that allows blood glucose to be stored as muscle glycogen without the use of insulin.

Note that this study by Newsom et. al. provides evidence that muscle glycogen is depleted the day after exercise if carbohydrates are not consumed in sufficient quantity during the 12 hours or so after exercise. Although the investigators made sure that participants were fed a meal withing 30 minutes of exercise, the study is not concerned with the brief period of enhanced, efficient glycogen storage that takes place immediately after exercise and provides no evidence one way or the other about the consequences of ingesting or failing to ingest sufficient carbohydrates immediately after exercise.

The results discussed in (B) provide evidence that fat metabolism is higher the day after exercise if fat intake in the hours after exercise is depressed. This is of interest to cyclists who are concerned with losing weight. Body fat is being burned at a higher rate the day after exercise if the fats burned during exercise are not replaced with fat in the diet. Note that there is no indication here one way or the other whether the increased amount of fat metabolism shown the following day is sufficient to produce noticeable weight loss. However, if you are interested in losing weight through the loss of body fat, increased levels of fat metabolism have to be better than no increase in fat metabolism in the long run. Note also that fat metabolism was increased in the Low Energy condition even though carbohydrate intake was kept high enough to replace the muscle glycogen lost to exercise. Taking in enough carbohydrate after exercise to replenish glycogen stores allows you to be ready for an exercise session the next day and does not stop fat metabolism that is breaking down body fat to supply energy.

In summary, what you eat after a ride makes a difference. It isn’t the case that calories ingested from fats are equivalent to calories ingested from carbohydrates when replacing the calories burned during exercise. Eating carbs after a ride replaces lost muscle glycogen, gets you ready to ride the next day, and does not stop fat metabolism. Refraining from eating fats after a ride increases the burning of body fat the day after the ride and does not interfere with glycogen storage. The take home message seems simple: Replace glycogen by ingesting carbs after a ride; metabolize fat and possibly lose weight by not eating fats after a ride.

Cycling Nutrition: Eating After the Ride

Posted on May 11, 2008 by Kevin Murnane

Post ride recovery in Ireland

The information in this post has been revised and substantially enhanced in Nutrition for Cyclists: Eating and Drinking Before, During and After the Ride which can be purchased on Amazon.com. The revisions include new information about the relationship between protein and carbohydrates in post-ride recovery based on research published after this post was written. The book also has new sections devoted to rehydration and glycogen, protein, and electrolyte replacement following the first hour after you get off the bike. For information about Nutrition for Cyclists and how it relates to what I’ve posted to Tuned In To Cycling, please check out this post.

I’ve seen this happen time and time again. Laura and I have had the good fortune to go on several bicycle tours that last one to two weeks. The tours are advertised for advanced or experienced riders and typically feature hilly or mountainous terrain and daily rides in the 60 to 125 mile range. You ride from place to place and a van carrys your luggage. The other riders on the tour are almost always experienced cyclists, at least in the sense that they have been riding for many years and are used to riding long miles. These tours usually schedule a day or two off when the riders are free to do whatever they want. This has always puzzled me. Why would experienced cyclists pay the steep cost of going on one of these tours, go through all the hassle of getting their bike to some exotic location, and then spend a day or two not riding in terrain that provides spectacular cycling? The people who run these tours obviously know more about it than I do because by the third or fourth day of the tour almost all of the riders are noticeably lacking in energy and enthusiasm, are irritably fretting about why they feel so tired, and are looking forward to the break. Meanwhile, Laura and I are riding extra miles every day because we’re having so much fun, are fresh and ready to go every morning, and are typically the only ones out on our bikes on the day off.

What’s going on? Why are we riding more miles with less overall fatigue than almost all of the other riders? I don’t know for sure, but I’m fairly certain the answer lies in post-ride nutrition. Many of these other riders are active members of their local cycling clubs. They shine on organized centuries and long weekend rides with members of the club. After the ride everyone goes out for ice cream or pizza and beer. They are clueless about post-ride nutrition and have given no thought at all to how what they eat when they get off the bike can affect how they will ride the next day and the day after that. They finish the first day in glycogen debt and fail to adequately replenish their glycogen stores before the next day’s ride. Every day the situation gets worse and the riding becomes more unpleasant until by the third or fourth day their blood sugar levels are so low they’re grinding it out with their head down and need a day off to physically and mentally recover. All of this can be avoided if you pay attention to what’s happening in your body when you get off the bike and take advantage of the opportunity your body gives you to prepare for strenuous activity on the following day. Most of it comes down to what you eat in the first 30 to 40 minutes after you get off the bike.

When you finish a long ride your glycogen stores are exhausted and you are very likely to have low blood glucose. Your body responds to the glycogen debt by going into overdrive to replace the missing glycogen. Excess glucose in the bloodstream is converted to glycogen and stored in the muscles and the liver. Under normal circumstances insulin is used in this conversion process. However, after an extended period of exercise when the muscle glycogen stores are exhausted an abbreviated and accelerated glycogen-storage process kicks into gear that converts glucose into glycogen and stores it in the muscles without the need for insulin. This period of intense glycogen production and storage lasts for 30 to 60 minutes.

In order to take advantage of this brief period of accelerated glycogen storage the system must have blood glucose that can be converted to glycogen. And there’s the problem. When you finish a long or intense ride you are almost certainly low on blood glucose. Your system is ready to rapidly and efficiently replenish your empty glycogen stores but it doesn’t have the glucose it needs to make the glycogen.

The solution is to flood your system with carbohydrates that can be quickly converted to blood glucose which will in turn supply the accelerated glycogen production and storage mechanism with the glucose it needs. Although the enhanced glycogen production mechanism will operate for roughly 60 minutes after exercise has stopped, keep in mind that it takes time for carbohydrates in the stomach to be broken down into useable blood glucose. Food you eat during the second half of that 60 minute window may still be in the stomach being digested when the enhanced glycogen-storage process ends. The first 30 minutes after you get off the bike are critical. If you are going to fully replenish your glycogen stores for the next day’s ride, you must ingest enough carbs during those 30 minutes to flood your system with glucose. If you don’t, it doesn’t matter what you eat for the rest of the day; you will be building on a weak foundation and you won’t have the glycogen reserves you need to ride with strength day after day. This cannot be stressed enough; you have to reload your system with carbs during the first 30 minutes after you get off the bike.

How many carbs do you need to eat during the critical 30 minutes? Current thinking holds that you should aim to ingest one half gram of carbohydrate for each pound of body weight during the 30 minutes after you get off the bike. This is easy to figure out; simply divide your weight in half and eat that many grams of carbs. For example, I weigh about 160 lbs so I need to eat 80 grams of carbs within 30 minutes of getting off the bike. There is also some evidence that combining these carbs with protein may facilitate the glycogen production and storage process. The recommended ratio of carbs to proteins is 4 to 1. Thus, at 160 lbs I need 80 grams of carbs and 20 grams of protein.

Eating enough food to provide this much carbohydrate in the first 30 minutes after you get off the bike can be very difficult. The 30 minute part is much more important than the specific amount of carbs and protein part. If you can’t manage to choke down the full recommended amount, eat as much as you can, but make absolutely certain you do it in the first 30 minutes after you get off the bike.

You can eat any kind of food you like as long as it’s high in carbs. Simple carbohydrates that can be more quickly broken down into blood glucose are better than complex carbohydrates that take a longer time because you need to get the glucose in the blood stream within a short window of time. There are two key factors that will end up driving your 30 minute carbohydrate feast; the food has to be available immediately when you get off the bike, and you have to be willing to eat it. The carb sources you’ve been eating on the bike will work equally well during this critical 30 minute window but you may be sick and tired of sports drink, energy gel, low-fat fig newtons or whatever you’ve been eating by this time. Laura and I drink a recovery drink called Endurox that contains carbs and proteins in the recommended 4 to 1 ratio. We find it’smuch easier to drink a large number of carbs than eat them immediately after a long ride. It’s also very easy to have the drink ready at the end of the ride. Endurox comes in a powdered form that you mix with water. We premeasure the powder, put it in a baggie, and carry it with us on the ride. Water is almost always available at ride’s end and we simply mix the powder with fresh water in our water bottle and chug it down. Although the manufacturer would have you believe otherwise, there’s nothing special about Endurox other than that we like the way it tastes. A number of companies make recovery drinks that provide huge carbohydrate loads for immediate post-exercise glycogen replacement.

After the critical 30 minute window, try to continue to ingest carbohydrate at regular intervals throughout the remainder of the day. Eat small amounts steadily rather than eating nothing and then pigging out at dinner. Avoid alcohol because it will interfere with the uptake of glycogen and will also dehydrate you. Avoiding alcohol is especially important immediately after the ride when the body is in the critical glycogen restocking period.

What you eat during the 30 minutes after you get off the bike is probably the single most important factor affecting how you will fare if you’re riding more than 90 minutes a day for more than 2 days. If you get the carbs you need during this 30 minute window, you can ride for days and days without problems; if you don’t, you’re most likely going to be tired and out of energy by the third or fourth day.

For more information about what to eat (and what to avoid eating) after a ride, see Eating After the Ride Part 2.