Is effective nutrition like a good joke – is it all about timing?
Thursday, September 28, 2017. Author Nathan West Ph.D.
Thursday, September 28, 2017. Author Nathan West Ph.D.
Recently the International Society of Sports Nutrition (ISSN) published their 'position stand' on nutrient timing, which is the consensus opinion of a group of extremely experienced and knowledgeable researchers, professional nutritionists, and trainers, supported by 175 scientific references, and peer-reviewed by an additional panel of independent experts. As well as being an excellent summary of the most up-to-date science, the review paper is also useful for coaches, trainers, nutritionists, athletes and any other individual who wants to optimize their nutrition. Here’s a summary of the main points:
What is 'nutrient timing'?
Nutrient timing is the purposeful ingestion of nutrients at specific times during the day to favorably impact the adaptive response to the short and long-term effects of exercise. In other words, eating at the correct times to improve things such as physical performance, recovery, muscle protein synthesis (MPS), nutrient utilization, body composition, muscle strength/power, VO2 max, etc.
While most of the research on nutrient timing has focused on competitive athletes or highly active individuals, nutrient timing is often considered an additional tool to help the “average person” better achieve their exercise and body composition goals.
In the 1970's-80's, the initial research on nutrient timing focused on the effects increased carbohydrate consumption had on glycogen stores and exercise performance. More recently, research has shifted to the timing of protein and amino acids (with and without carbohydrates) in the diet. There is unfortunately very little information on the timing of fat consumption, so this was excluded from the report.
The report concludes that you can maximize your body’s glycogen stores by consuming 8-12 g of carbohydrate per kg of total body weight per day. For a 75kg individual, that equates to 600-900 g of carbs or roughly 2,400-3,600 calories. Now, some of you are saying, “That’s a lot of carbs and I would get fat if I ate that much.” You're probably right - but bear in mind that this is a recommendation for male endurance athletes doing upwards of 12 hours training per week at moderate to high intensity.
Carbohydrates before endurance exercise
For most of us, eating such a high amount of carbs is only appropriate when participating in activities likely to deplete our glycogen stores, such as competing in an endurance event or doing a training session lasting more than 90 minutes. Eating like this before an endurance event is commonly known as "carb loading" and usually involves consuming a very-high carb diet in the 1-3 days leading up to an event/session. Think of runners piling up plates of pasta before a marathon. Some people choose to deplete their glycogen stores before carb-loading. Whether or not this is required is still being debated.
As well as increasing carb intake in the days before a long endurance session, for optimal performance it’s advisable to also consume carbs (meals or snacks containing 1-4 g per kg) in the hours just before a session. This is especially important for people who haven’t eaten sufficiently in the run-up to an event, either through necessity (e.g. – a weight cut) or through lack of preparation (e.g. – not eaten enough, not rested/recovered properly). Both liquid and solid carbs can be consumed. The exact type and amount of carbs is down to the individual and what their digestive system can tolerate.
Carbohydrates during endurance exercise
During long, intense sessions it is important to continually refuel by taking on carbs. The ISSN recommend 30-60 g (depending on body size/composition and tolerance) of carbohydrate per hour, ideally in 6-8% carbohydrate-electrolyte solution (6-12 fluid ounces or 170-340 ml) in small amounts every 10-15 minutes.
Carbohydrates after endurance exercise
Post endurance exercise, it’s crucial to replenish lost glycogen. The sooner (within 30 minutes vs. 2 hrs) carbohydrates are consumed post-exercise, the higher the rate of glycogen replenishment.
According to the research, 0.6-1.0 g of carbs per kg of body weight within the first 30 minutes post-exercise and then every two hours for the next 4 to 6 hours was shown to induce maximal glycogen replenishment. 1.2 g per kg every 30 minutes over 3.5 hours had a similar effect.
However, this is only really needed for people requiring rapid glycogen replenishment, such as those training twice daily or partaking in prolonged (85-90 minutes or more) intense exercise on consecutive days. Where rapid recovery/replenishment is not required (i.e. - most of us), matching your daily energy demands is more important than the timing of your carbohydrates. In simple terms: for most people, it’s how much rather than when you eat that matters.
Carbohydrates and resistance exercise
Reduction in glycogen stores during resistance exercise is modest and often overstated compared to intense endurance exercise. You can still effectively perform resistance exercise under moderate glycogen depletion. While taking on carbs during resistance exercise does maintain muscle glycogen stores, it doesn’t seem to have a significant impact on performance under normal conditions (i.e. – not completely glycogen depleted).
So, for the average gym goer, carbs are not needed during a workout. As long as you eat enough carbs throughout the day to meet your daily energy demands, you should be fine. For someone exercising more than once a day, taking on carbs during, between, and after sessions will be more important and help maintain/maximize glycogen stores and performance.
Carbohydrates + protein and endurance exercise
Consuming a mixture of carbohydrate + protein before, during, and after a bout of exhaustive endurance exercise will help improve performance and reduce muscle damage. This may be particularly useful for people who cannot tolerate eating carbohydrates during or just before exercise – you can substitute protein for carbs. Also, if you have a short window of recovery between bouts of exercise, or if you eat sub-optimal amounts of carbohydrates, then adding protein can help glycogen replenishment and reduce symptoms of muscle damage.
Carbohydrates + protein after endurance exercise
There are conflicting reports on the benefits of consuming carbohydrates + protein post-exercise to maximize glycogen replenishment. Some studies show a positive effect, while others show no improvement over-consuming carbohydrates alone. However, it appears that glycogen replenishment is augmented by protein when carbohydrate ingestion is low (less than 1.2 g per kg per hour). 0.2-0.4 g of protein per kg per hr seemed sufficient to aid glycogen replenishment and reduce muscle damage.
Carbohydrates + protein and resistance exercise
Consuming carbohydrate + protein or essential amino acids (EAA – the amino acids your body cannot synthesize and must get from your diet) before, during or after resistance exercise has many positive effects. This combo can decrease cortisol (a stress hormone) levels and markers of muscle damage, stimulate muscle protein synthesis (MPS), help aid long-term adaptations (e.g. – hypertrophy) and improve performance.
Combining carbs + protein seems most important when the availability of protein is low. For example, when sufficient amounts of protein (containing at least 10-12 g of EAA or just EAA alone) are provided around training, MPS is maximally stimulated. When less protein is consumed, the addition of carbs helps rescue maximal MPS stimulation.
Protein and resistance exercise
Protein helps build muscle. But how should you time your protein intake? A 20 g dose of whey protein or 25 g dose of a blended protein (a mixture of whey, casein, egg white and glutamine) before or after a workout has been shown to stimulate MPS. It’s a good habit to consume protein within 2 hours after a workout, but the exact timing is unlikely to significantly impact muscle synthesis – so don’t lose too much sleep over missing the “anabolic window”. It is more important to consume sufficient doses of protein throughout the day. Spreading your total protein intake throughout the day into adequate portions (~20-40 g) and consuming it every 3-4 hours should aid consistent MPS.
Protein during resistance exercise
Athletes completing high training volumes (>12 hrs per week) and multiple sessions per day may benefit from consuming protein during a workout. If you’re doing a lot of weight training, you need to eat regularly and consume a large amount of protein, so having protein during a workout can be beneficial especially if you are struggling to eat enough throughout the rest of your day.
Pre-sleep protein intake
Should you eat just before going to bed? Studies suggest that a shake containing 30 g of whey, 30 g of casein and 33 g of carbohydrates consumption, 30 minutes pre-sleep, result in elevated morning resting metabolic rate. In both short and long-term studies, pre-sleep protein consumption has been shown to be advantageous for MPS, muscle recovery, and overall metabolism. However, the exact timing of protein intake may not be as important as eating sufficient total protein spread throughout the day.
1. Making sure you eat enough is more important than when you eat
The total amount of calories and macronutrients are more important than the timing of any single nutrient or meal. Think of the total caloric and macronutrient intake as the foundations and structure of a building. Everything else (timing, supplements and even to a certain extent training) are the aesthetics and decoration. Without both the foundations and structure, a building will collapse, and so will your fitness goals, whether that is fat loss, muscle building or a more specific athletic endeavor.
2. Carb load if you have a long endurance event and want to optimize performance
3. Spread protein intake out throughout the day, including eating protein at breakfast
4. Eat mostly mixed meals (e.g. – meals containing at least carbs and protein sources). This is the best way to replenish glycogen stores and stimulate MPS and recovery
5. Do not be afraid to eat close to bedtime if you haven't consumed all your allocated calories for the day.
6. The more specific your training goals, the more specific you need to be with nutrient timing. Athletes who train hard multiple times a day and/or many hours a week need to think more about what, when and how much they eat than the average person who exercises 3-5x per week, “just to keep fit”. This is partly because the more serious athletes are limited by short recovery between sessions/events.
One thing that wasn't really covered in this otherwise excellent paper was the effect of nutrient timing or meal frequency on appetite, hunger levels and aiding fat loss. Again, this need not be overly complicated for someone looking to shed a few pounds, but someone looking to get shredded might need more stringent nutrient timing information. At FitnessGenes we give you genetically tailored nutrition advice to help you manage your hunger and appetite levels and to better achieve your fitness goals.
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