By Matt O'Neill, MSc(Nut&Diet), APD
Twitter | Facebook | LinkedIn
Nutrient timing is the hot new nutrition term buzzing around gym floors and PT classes. With a mountain of mixed information on the topic how can you put the science of eating around exercise into practise? In this article I show you how to decide what to eat and when.
Nutrient timing involves consuming specific nutrients in the correct amounts at particular times before, during and after exercise to optimise performance and body composition.
It's an attractive proposition that you could reward yourself with better physical results from your training just by getting food timing and selection right. Body builders have been disciples of nutrient timing for years, chugging down protein shakes during workouts rather than risk a metabolic shortage of vital nutrients.
In recent years, weight-pit trial and error has transformed into hard core scientific trials to explain how and why nutrient timing works. Here's what the latest science has to share and real-world implementation advice.
First, choose your goals
If you just want to become more active and drop a few kilos you won't need to become a nutrient timing stickler who monitors every mouthful down to the minute. Simply eating fewer calories every day and getting to the gym on time will deliver the reduced waist line you desire.
But if you are a fitness enthusiast or athlete who wants to build a better body and optimise muscle levels for performance, the evidence is mounting that nutrient timing will give you the edge. What you eat before and after your exercise sessions may now be just as important as your day-to-day diet, especially for building muscle size and strength.
Getting it right will still take some personal experimentation, especially when you'll be juggling nutrients, hormones and workouts. Any body builder will tell you it's hard to gain massive amounts of muscle in an anabolic (growth or bulking phase) whilst minimising body fat. Reducing body fat is best achieved during a catabolic (leaning or cutting up phase) which if too severe or extended for too long can deplete body protein and shrink muscles.
Your results will depend on your body composition, training effort, attention to diet and genetics. The balance you arrive at may vary from your initial objective based on your experience. For example, you may be able “lean-up” and cut body fat but the considerable effort it takes means you can only stay at a lower body fat level for a few weeks until you need to relax the regime.
Now, let's look at your nutrient timing before, during and after exercise.
If you already have enough carbohydrate stored in your body in the form of muscle glycogen, the carbohydrate you eat in the hour or so before exercise may make little difference to exercise performance.
But carbohydrate combined with protein (co-ingestion) 30 minutes pre-exercise can result in peak levels of protein synthesis after training. Amino acids available from the outset of training and increased blood flow during exercise are thought reduce acute muscle damage and enhance protein replenishment after training.
Adding protein pre-workout may even increase blood levels of growth hormone and testosterone, which are key anabolic hormones.
Pre-exercise feeding studies have used varying mixes of carbohydrate and protein with success so you may not need to be exact. However, the International Society of Sport Nutrition (ISSN) recommends 1-2 grams / kg carbohydrate and 0.15 - 0.25 grams / kg protein.
From experience, for a 75 kg individual this means a practical target of 10-20 grams of protein most of which should be consumed 30 minutes before a workout. The 75-150 grams of carbohydrate can be split up between a meal 2-3 hours before and 30 minutes before training.
The traditional fuel source recommended during exercise has been a sports drink with 6-8% carbohydrate. A target of 30-60 grams of carbohydrate per hour when exercising for more than one hour is prudent.
Now, the addition of protein at around one quarter of the carbohydrate hourly dosage has been found to improve endurance and resistance training performance.
Recommended protein ranges from between 6 -15 grams per hour during training. Specialist sport drinks with added protein offer a convenient source of both nutrients, but the taste and texture may not be appealing.
Co-ingestion of protein with carbohydrate during early recovery from exercise can enhance muscle glycogen synthesis, particularly if carbohydrate intake is less than optimal. Dietary protein after exercise will also increase synthesis of muscle proteins.
Studies have revealed benefits with post-workout timing ranging from immediate feeding up to three hours later. Even so, a replenishment window of 30 minutes is often used to keep stimulating the rebuilding process.
The target mix is similar to that before exercise with a 4:1 ratio carbohydrate to protein. With 1.2 grams / kg the target for carbohydrate, this requires a 0.3 gram / kg protein dose or 22 grams for our 75 kg exerciser.
Although the nutrient timing protocols outlined are what the latest science says works, what you find works in terms of results and practicality may vary. Start by checking what you usually eat or drink around exercise sessions. You may be surprised to discover that chocolate milk delivers around a 4:1 ratio of carbohydrate to protein.
Lastly, keep in mind that the amounts of nutrients discussed in this article relate to individuals who are exercising strenuously for either aerobic or strength training often for over an hour at a time.
If you are not exercising at this level or need to reduce body fat significantly, it may be more appropriate for you to focus on improving your core diet and getting your calorie intake correct. If you have graduated your training and physique to a higher level of performance, nutrient timing could offer you additional rewards.
Kerksick, C., et al., International Society of Sports Nutrition position stand: Nutrient timing, Journal of the International Society of Sports Nutrition, 5:17, October 2008 (Available for download free from http://jissn.com/content/5/1/17)
Get Matt O'Neill's monthly SmartShape eNews
MORE FROM SMARTSHAPE
Download a webinar or attend a live event
Enrol in the Weight Loss Coaching Course
Follow Matt O'Neill