The carbohydrate has had a bit of a hard time recently. Carbs make us fat, sugar is evil, and we should all switch to a high-fat diet or we will get diabetes. While that may sound extreme it certainly isn’t a rare opinion. We, humans, love to see things in black and white and nowhere is a better example of this than in the fitness and nutrition world.
People love to put themselves in one group or another. Try telling a cyclist they should do some strength work, or tell a bodybuilder a bit of cardio won’t make their training go amiss and you’ll quickly find yourself in an argument. It is a similar situation with the popularity of low-carb diets. There is some basis for advocating a reduction in carbohydrate consumption, especially refined carbs, and simple sugars. But does that mean we should all go from the classic high-carb diet to a ketogenic diet?
The more we learn about the human body the more we realize that, while there are some basic concepts that work for everyone, the “one size fits all” diet just doesn’t exist. Rigidly sticking to any dietary dogma is not going to be very helpful in your journey towards your training goals let alone your mental well-being. You have to be flexible with your diet and this is the fundamental concept of periodized nutrition.
Most people who read this site will be familiar with the concept of periodization of training, the progressive approach to planning training as you move towards your goal. Periodized nutrition (or nutrition periodization) can be thought of as tailoring your diet to meet the demands of your current training regimen. In the same way that you should be planning your training, you should be planning your nutrition. Below I am going to give an example of when deciding to reduce your carbohydrate intake is a good idea and also when it is not.
Evaluate Your Carbs
When thinking about how much or how little carbohydrate to include in your diet you should ask yourself two questions:
- What is my current goal?
- How hard is my current training regimen?
These may seem like very simple questions, but they can keep you focused on benefitting as much as possible from your diet. Do you want to lose weight? Do you want to gain weight? Are you a football/rugby player who plays a match every weekend and trains twice a week? Do you have a marathon next month? Are you training for an Ironman? Whatever your current goal is it will have a direct effect on how hard your training sessions are and also your dietary needs.
Nutrition Coach Baz Wakelin of Valladolid, Spain
Notice how I have said “current goal”—it is possible to have several athletic goals throughout the year. For example, somebody who has an Ironman event in August may want to lose a few kilos in January, therefore their training and diet will look very different in the winter than it will in the late spring.
When to Go Low Carb
Without getting lost down a biochemistry rabbit hole we can work with the generalization that if we take on more energy than we expend we will gain weight. Obviously, from the science point of view it is more complicated than that, but from a practical point of view of it really doesn’t have to be complex.
But why should we reduce carbs and not fat or protein? The simplest answer is because the carbohydrate usually makes up the largest proportion of our diet (often at least 50%), so if we reduce our carbohydrate intake we are reducing our overall energy intake. The more complicated answer is when carbohydrate (glucose) is being used as a fuel it reduces lipolysis, the process by which fat is used as a fuel. To add to this when energy intake is higher than demand (i.e. we are eating more than we need to once muscle and liver glycogen stores are filled) the excess glucose is converted to fatty acids and sent to the adipose tissue to be stored as body fat.1
So, carbohydrate hinders fat utilization and can be stored as body fat pretty easily. In terms of protein intake, while it is also possible for excess protein to be converted to fatty acids and stored as fat, this rarely happens and current evidence suggests that during dieting protein intakes should actually be increased in order to preserve muscle tissue.2 I’m fairly certain I don’t need to explain why preserving muscle tissue is a good thing. In our clinic, we often see an overreliance on animal protein so we change some for vegetable sources to increase fiber content of a diet. But in terms of total amount of protein, we rarely see someone who is overdoing it.
When my partner and I are assessing somebody’s diet who wants to lose weight the first two places we look are alcohol intake and what we call “junk” or “wasted” calories. Alcohol is an obvious one, but it is difficult to deal with because often you can’t get an honest answer from your client about their alcohol intake and/or they are unwilling to significantly reduce it. But if you are serious about your diet and your training goals then reducing your boozing will only have positive effects.
Moving on to the wasted calories, in our experience, these are nearly always excess carbohydrate, usually in the form of added sugars, which can easily be removed from the diet. Breakfast cereals, fizzy drinks, pasta, rice, and potatoes—these are all things that can be reduced or removed from your current diet quite easily without having to go to the extreme of a ketogenic diet.
Ultimately, if you want to lose weight or improve body composition and/or your training load is not particularly high then a reduction in carbohydrate intake will be helpful. In terms of numbers, between 3g and 5g per kg of body weight is the current recommendation.3 If you keep a diary of your intake on an online tracker, which if you are trying to diet I recommend that you do, then you will notice you can hit that 3-5g/kg amount pretty easily, so we always recommend getting most of your carb intake from vegetables and legumes before touching the pasta, rice, etc. to ensure a good intake of fiber and micronutrients.
Another area of interest within nutrition periodization and low carb living that has increased in popularity recently is the idea of “training low.” This is essentially training with limited access to or complete avoidance of carbohydrate, or training in a state of glycogen depletion. The proposed benefits include increased protein synthesis and increased fat oxidation, the double Holy Grail for strength and endurance enthusiasts alike.4
There are several methods of training low, but the most widely used is probably fasted training. I would wager that most early morning exercisers (or those that ride/run to work) perform fasted training without intention. It is basically training before you have breakfast.
Early research is promising regarding this method of training, especially in terms of increased fat oxidation. However, it is too early to give specific recommendations in terms of duration, frequency, etc. If you want to include fasted training into your program I would recommend keeping the duration quite short (around 60 minutes) and keep the intensity low.
When Not to Go Low Carb
At first glance, the reasoning behind advocating a low carb even ketogenic diet is pretty sound. We only have a small amount of stored carbohydrate (stored as glycogen in the muscle and liver), whereas we all have a practically limitless supply of body fat. Why not teach the muscles to preferentially use fat as a fuel and leave the precious carbohydrate to tissues that use glucose either exclusively or preferentially, such as red blood cells or the brain?
The problem with low carb or ketogenic diets is with performance. Several studies have shown that following an LCHF (low carb high fat) diet will certainly increase your capability to use fat as a fuel, but sadly this does not translate into improved performance.5 The advocates of the LCHF movement often cite research showing improved TTE (time to exhaustion) after reducing carb intake to a minimum and becoming what they term “keto-adapted”—the process by which your body has begun to use ketones as a major fuel source.6
There is a rather large “but” here and it is the fact that TTE studies are not performance studies. TTE is as it sounds, a participant exercises at a given intensity until they are completely exhausted and have to stop. Can you think of a single sport where the athletes all start at the same time and keep going until they drop one by one? You won’t be able to because such a sport does not exist. The results from TTE studies are usually extrapolated to endurance sports, but the aim of endurance sports is to get from point A to point B in the quickest possible time. This is an important point because it renders TTE and LCHF studies useless in another way and that is that often the studies are performed at a moderate intensity (from 50% – 70% VO2 max), which, if anyone has run a marathon, done a triathlon or raced a bike will know that these are all performed at an intensity much higher than 70% VO2 max, often with periods of near maximal effort.
Once we get past a certain intensity, whether we are “keto-adapted” or not, our bodies will begin to use only carbohydrate as a fuel source because the process of using fat is just too slow. Of course on paper the LCHF idea sounds perfect, we use more fat at the lower intensities and save more of our glycogen for when the going gets tough. The problem is that it appears that becoming keto-adapted hinders our ability to use muscle glycogen, so when we need it most we can’t access it.5 In a recent study by Louise Burke at the Australian Institute of Sport7 she revealed a performance decrease when elite race walkers switched from their habitual diet to an LCHF one, it is worth noting they used a performance test (a race) not TTE.
In terms of resistance training, while lifting weights does result in glycogen depletion, it is not currently thought to be the limiting factor in performance unless you are training more than once in a day or have not recovered properly and are starting a session with depleted glycogen.8 Even though many people do not train more than once a day, those that have a physically active job who then train in the evenings should keep in mind that they need to replenish their glycogen stores if they plan a hard session after work. This should be taken into account by team sports players, especially sports such as rugby where players would probably train in the weight room during the week and then play a match on the weekend. You would want to ensure your glycogen stores are replenished come match day. To add to this, consuming carbohydrate (around 1g/kg body weight) after a workout with your usual post workout protein has been shown to decrease muscle protein breakdown.8 This is ideal for those of you who are wanting to gain muscle mass.
When performance is the goal of your training or you are mid-season or even if you simply want to gain muscle mass then following a low carbohydrate diet would not be optimal for your training needs. Current guidelines are 5-10g/kg body weight of carbohydrate. I would advise the lower end of that scale as realistically only professionals would require more than 7g/kg.3 And remember to include at least 1.6g/kg of protein from a mixture of animal and vegetable sources.
Periodize Your Nutrition to Work for You
When thinking about the periodization of your nutrition in relation to carbohydrate intake, following either a low or high carb diet throughout the year is not going to be optimal and may be in fact detrimental to your training and performance. If you want to lose weight and/or you are not currently training particularly hard, then reducing your carb intake is certainly worth considering. Conversely, if your training load is high at that particular time, you are mid-season or if you want to bulk up, then you will need to consume a moderate to high amount of carbohydrate depending on how hard you are actually training. By “high training load” I mean 1-3 hours of daily training not spending most of your gym time taking selfies or spending your group rides sitting in the wheels pushing 130 watts.
1. Gropper S.S, Smith J.L, 2012. Advanced Nutrition and Human Metabolism. Wadsworth
2. Stokes T. et al. 2018. Recent Perspectives Regarding the Role of Dietary Protein for the Promotion of Muscle Hypertrophy with Resistance Training. Nutrients. 10, 180.
3. American College of Sports Medicine, 2016, Nutrition and Athletic Performance. Medicine and Science in Sports and Exercise. 48 (3) p543-568.
4. Jeukendrup, A, E. 2017. Periodized Nutirition for Athletes. Sports Medicine. 47 (Suppl 1)
5. Burke L.M, 2015. Re-examining High-Fat Diets for Sports Performance: Did we call the Nail in the Coffin Too Soon? Sports Medicine. 10, 1007.
6. Volek J. Phinney S. 2012. The Art and Science of Low Carbohydrate Performance. Beyond Obesity LLC.
7. Burke L.M, 2016. Low Carbohydrate, High Fat Impairs Exercise Economy and Negates the Performance Benefit from Intensified Training in Elite Race Walkers. Journal of Physiology 595 (9) p2785 – 2807.
8. Campbell B, 2014. Sports Nutrition, Enhancing Athletic Performance. Taylor and Francis Group LLC.