Timing of Carbohydrates
The most important factor with regard to body composition and performance is eating a diet that provides a calorie deficient / surplus / balance and long term adherence. Timing of nutrients will have little long term effect, if you are under / over eating relative to your goals (1).
However, If two diets provide equal macronutrients and calorific intakes then it could be suggested that the diet that provides better calorie portioning (Ie. Where calories are directed) will have a more significant impact on body composition, well that’s the theory anyway. A factor that influences where calories are directed is when they are eaten in relation to exercise.
Let's look at the key timing periods below:
Pre training: This is one of the times that eating carbs can have a significant effect on performance, particularly for longer sessions. When carbs are eaten at this time they provide a number of functions (2, 3).
Top up carb stores; provide readily available energy for the upcoming session rather than being stored for later use.
Help Spare muscle glycogen which comes in useful at the end of a long chipper, AMRAP or hero wod.
Helps the uptake of amino acids from pre training protein into the working muscles helping to limit muscle breakdown during a session.
How much you eat you pre training is going to be down to individual preference, how close to the session you eat and your goal, whether it be body composition based or performance. Additional it was suggested that pre exercise carbs would hinder fat burning and slow the rate of fat loss, but as we know, acute reductions in fat burning don’t result in impaired fat loss over a longer time frames and since Crossfit WODs burn through a load of carbs rather than fat to power the sessions it makes sense to fuel the body for performance to get the most out of the session, this may translate to higher exercise intensities being maintained with the knock on effect being a greater post exercise metabolism and higher levels of fat burning for up to 24 hours after the WOD (4).
So pre exercise carbs, improved exercise performance and the possibility of greater long term fat burning sounds like a win: win to me
During Training: The need for these really depends on your training goals and diet set up, The need for them for the average crossfit session lasting less than 60 minutes is pretty much nil with regard to enhanced performance
(3) , but could be useful when using a targeted carbohydrate diet (i.e. only eating carbs at specific times in order to maximise where they are directed and used) using them during training means they will be used up at a time when the body is efficient at using carbs, Limiting carbs to during and post training is often an approach used in those that are less sensitive to carbs at other times of the day. For those that train with high volume or do multiple training sessions per day, carbs during training may aid recovery for later sessions and improve performance during longer sessions while preventing muscle breakdown during the session its self (1). The need for carbs during training is determined by your goals and diet set up, hence there is no requirement to have then during a session. Interestingly there is emerging evidence that simply using a carb based drink as a mouth wash during training may improve performance by activating the reward centres in the brain, without having to digest the calories, although research is still conflicting with regard to how significant this effect may be. This could be useful for those managing carb intakes in relation to their goals while stilling looing to maximise performance (5)
This is the traditional time where we have all heard we should be eating our carbs to refuel. There is certainly truth to this and it is a time we should aim to take advantage of, but once again hitting daily macronutrient targets is more influential for recovery then simply eating carbs straight after training. If your only training once a day and there is at least 24 hours between sessions, then as long as total carbohydrate intakes are met, muscle glycogen storage will be comparable to eating a ton of carbs post training and not at any other time between the sessions, this does however change as the recovery period between sessions decreases and taking advantage of this post training window of opportunity becomes more important.
During the initial post exercise stages of recovery Glut 4 (Up regulation of Glut 4 protein expression, results from muscular contraction and glycogen depletion) levels are at their highest which allows for carbohydrates to pass through the cell membranes more easily and without the need of insulin to help ‘push’ the carbs inside the muscles (6, 7). This means that any carb source can be used post exercise to restore muscle glycogen even in the presence of fat which was initially thought to hinder the process (8). This causes our muscles to store more carbs as glycogen as they are more insulin sensitive and your fat cells are less insulin sensitive. This means that your muscles will act like a sponge to absorb incoming carbohydrates as a way of restoring the carbohydrates that have been used for energy during exercise. (9).
The longer the duration or higher the exercise intensity of exercise, the greater your muscles sensitivity to insulin = better direction of carbohydrates towards muscle.
As crossfitter’s, we love to train. But sadly the body needs a couple of days off from time to time to help us recover from the hammering that it’s been given. On these days nutrition can change slightly as expenditure isn’t as high. Total calorie and carb intake can be reduced, how much (if any at all) is down to your goals
Fat loss: Reduce calories / Carbs by 20%
Maintain: Eat at an energy balance, maybe reduce carbs and increase fat slightly depending on your general activity levels.
Muscle gain / Maximise performance: Keep eating as normal, maintain a calorie surplus and maximise recovery from training.
Previously it has been suggested that carbohydrates should be eaten in the morning and avoided after 6pm as after that time they would be converted to fat. This is one of the long standing myths in nutrition and is simply not true. New evidence is suggesting that eating the majority of your daily carbohydrates in the evening may actually have a more positive effect on body composition (10, 11)
This may be for the following reasons
1) Your body is able to mobiles and burn fat more efficiently when insulin levels are low, this occurs after a fast (i.e. when we have slept overnight). When carbohydrates are eaten insulin levels are then raised which inhibits fat burning until they return to fasting levels. First thing in the morning insulin levels are at their lowest so your body is in the best metabolic position to burn fat better than at other times of the day compared to if carbohydrates are eaten earlier on in the day. It is also suggested that insulin sensitivity in muscle may increase during the day as a result of keeping carbohydrates low allowing greater partioning of calories towards muscle and away from fat. This effect is further enhanced if exercise is performed later on in the day or evening. This is ideal for people who exercise in the evening after work
2) Eating carbohydrates in the evening is associated with improved sleep quality as they cause the release of serotonin from the gut which is then up taken by the brain and has a relaxing effect which helps induce sleep. Improved sleep quality is strongly associated with greater control of hunger /cravings, blood sugar control, increased metabolism, reduced stress hormone (cortisol) release and higher levels of growth hormone and testosterone which are required to help burn fat.
3) Eating the majority of your daily carbohydrate intake in the evening by prevent hunger the following day by changing your hormonal curve as there a 8 to 10 hour time delay from when we eat carbohydrates to when a hormone called leptin is released. This hormone helps prevent hunger; hence by eating carbs in the evening it means that this hormone peaks the following morning, limiting hunger and cravings.
(11). Alternatively, for those that experience cravings and hunger in the evening, placing the majority of carbohydrates at the start of the day may prevent evening craving and hunger due to the same time delay in leptin, within peaking in the evening. This highlights how important it is to listen to your body and understand how your body reacts to different eating schedules.
4) From a social and behavioural point of view, it make may make sticking to a eating plan easier as you can eat a 'normal' evening meal with other people that may not be following a specific diet. In England the evening meal tends to be the one that is most commonly eaten with other people. Eating carbohydrates in the even allows for breakfast, lunch and snack to be controlled while limiting the effect that it may have on others. Evening meals can then be based around carbohydrates as is typically done in the western world. This also allows for a flexible approach to coping with evening meals out, parties and other social gatherings revolving around food as day time meals can be controlled without impacting others, which is often be a barrier to dietary adherence.
It is important to note that only eating carbohydrates in the evening is not a rule that has to be followed, but rather it may be an approach that may fit in with your lifestyle or one that can be used to cope with a specific event or situation. The most important factor is whether is allows a way for you to eat that you can maintain and be flexible with it. Take notes about how your body responds to different eating patterns a see how areas such as hunger / cravings / energy / concentration change if you eat a different way. Science can provide and disprove pretty much anything, at the moment it is leaning towards eating more carbs in the evening, but that can change easily if new research suggest otherwise.
Take Home Point: If eating the majority in the evening works with your lifestyle then you my gain a slight advantage with regards to improved body composition. However, if you prefer to have carbs spaced out throughout the day, the fact that you are able to adhere to that eating style is likely to help maintain progress over the long term, after all, eating the right account in total is going to outperform a diet that eats the wrong amounts but at the right times.
Fuelling the work required - Carb Cycling
Carbohydrate cycling is when your carbohydrate intake varies from day to day, allowing for lower carbohydrate, higher fat and protein intakes on some days and lower fat and protein intake on others while increasing carbohydrate intake, This allows flexibility within a diet while limiting the possible negative effects of a standard low carbohydrate diet. There is no right or wrong way to cycle your carbohydrate intake and it can easily be combined with and structured exercise programme (12)
* Allows the benefits of a low carbohydrate diet while limiting the possible negative hormonal effects of a continuous low carbohydrate.
* Raising carbohydrates regularly helps prevent a drop in leptin and thyroid hormone, preventing metabolism from falling. While controlling the stress hormone cortisol, which can be increased during periods of low carbohydrate intake as a way of raising low blood sugar levels
* Provide a progressive way to a more contestant low carbohydrate diets if an individual finds that way of eating suitable and maintainable.
* Provides psychological relief as only a couple of days of carbohydrate restriction maybe required bore such foods are eaten again, this makes adherence to such a eating plan easier
* Provides flexibility to a eating routine, for example an individual could
* Carbohydrate intake can be matched with exercise duration and intensity. As carbohydrate fuels high intensity exercise more carbohydrates could be eaten on training days which would allow greater partioning towards muscles, improve exercise recovery, while on days that an individual is not exercising and is less active, hence less carbohydrates are being used by the body for fuel, as such less are required by the body. This works well if your box posts workouts in advance, if you know tomorrows session you can match your carb and calorie intake relative to the sessions volume, with heavy lifting low volume sessions needing less total carbs on that day and lighter lifting but high volume lifting, gymnastics and monostructual work needing more carbs. As the nature of Crossfit is that it is constantly varied it allows for carbs to be cycled quite efficiently as the volume of a session is unlikely to constant.
An Example of carb cycle would be
Rest days: Lower carbs relatively speaking, eat them at times which suits you the best
Low volume session: training (21 -15 -9 / strength only / deloads etc: As above, but with an additional portion of carbs post training (i.e. 1 fist full portion if carbs)
Moderate volume (5 – 12 minute AMRAPS / Monstructual component): As above , but with addition portion of carbs pre training (i.e. 1 fist full portion of carbs pre and post)
High volume (12 – 20 Minute AMRAPS / Hero wods / longer Monstructual component). As above but 2 portions of carbs both pre and post, or carbs during the session (i.e. 1 fist full portion if carbs pre and post)
The important point is that low, medium and high carb intake is relative to the individual, so what is low for one person as an absolute amount could be high for another (hopefully part 1 helped you out with this). There is no right or wrong way to cycle carbs so trial and error is the key and noting how you feel on high, medium and low carb days, how performance is effected, how well you are recovering and how easy it is to adhere to, especially when living / eating with other people that don’t follow a carb cycling based plan. All these factors will influence the extent to which you may cycle carbs from day to day.
- Pre training carbs may be useful to provide energy for Crossfit sessions that are heavily dependent on carbohydrate
- During training carbs is likely to have little impact on performance if previous meals have been eat and sessions are shorter than 60 minutes
- Post training carbs are directed more readily towards muscle tissue to help restore depleted glycogens that Crossfit sessions heavily rely on
- Nutrient timing is less important than reaching specific macronutrient targets, the greatest peri-training nutrition protocol will have little effect if the rest of the diet as a whole is taken care of.
- Timing becomes more of a factor when recovery periods between sessions are reduced.
There is no need to be worried about eating carbs, firstly focus on the total amount of carbs you may required then worry about timing of those carbs after that. Placing these carbs around training is likely to improve performance and recovery, and this becomes more important when there is a reduced time period between sessions. On Rest days place carbs wherever you feel they help you maintain adherence, placing them in the evening is looking on paper to be the most efficient place to put them, but from a practical point of view personal preference should dictate when you eat them.
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9) Kerksick C et al, International Society of Sports Nutrition position stand: nutrient timing. J Int Soc Sports Nutr. 2008 Oct 3;5:17
10) Keim NL, et al. Weight loss is greater with consumption of large morning meals and fat-free mass is preserved with large evening meals in women on a controlled weight reduction regimen. J Nutr. 1997 Jan;127(1):75-82.
11) Sofer S, et al. Obesity (Silver Spring). Greater weight loss and Hormonal changes after 6 months diet with carbohydrates eaten mostly at dinner. 2011 Apr 7.
12) American Association for Cancer Research. Intermittent, Low-Carbohydrate Diets More Successful Than Standard Dieting, Present Possible Intervention for Breast Cancer Prevention. 2011
About the Author: Paul Johnson
Paul holds and BSc in Sport & Exercise Science and MSc in Exercise & Nutrition Science, while being accredited by the SENr (Sports & Exercise Nutrition register). He works full time as a Exercise referral specialist working with cardiac rehab, COPD, chronic pain patients. While coaching both training and performance nutrition to functional fitness and indoor rowing athletes online , While as an athlete himself he has competed in Crossfit and currently hold 4 British Indoor Rowing records.
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