Nate Miyaki is a fitness author, personal trainer and nutrition consultant, and the author of The Truth About Carbs: How to Eat Just the Right Amount of Carbs to Slash Fat, Look Great Naked & Live Lean Year-Round. He is based in San Francisco, California.
There is so much noise around the issue of ideal carbohydrate intake for optimal performance that it can be hard to separate the fact from the fiction when trying to ascertain exactly how many carbs you need per day to be at your best.
But the answer to this all-consuming question is actually quite simple. You need to apply the principle of specificity to your diet programme, just like you would to your training programme. Anyone who has dared to ‘take a walk on the iron side’ has heard of the SAID principle of specific adaptation to imposed demands. Good coaches utilise this principle every time they design a targeted training programme.
It may sound complicated but all it means is that your body adapts to the type of training that you do. You simply have to match your training programme to the specific physiological demands of your sport in order to attain optimal results. It’s really just using common sense rather than a complex or mysterious process.
What does this mean in reality? That the training for a powerlifting meet is different to that of a CrossFit competition, which is different to that of a bodybuilding show, which is different to that of training for the Bedroom Olympics. Of course there is overlap amongst them all, but there are clear distinctions in terms of the details and variables of the programme.
Matching diet to activity level
The specificity principle is equally applicable to designing targeted nutrition programmes in that you need to match your diet to your individual situation, metabolic condition, training regime and specific performance or physique goals. What is your take on low-carb diets? Given the answer above, I’m assuming you like them for some and not so much for others? And that’s exactly right. For certain people with certain aims low-carb diets can work like magic. For those with different goals, they suck.
Lower carb diets may be the best approach for improving body composition, and biomarkers of health for obese, insulin resistant, and sedentary populations. You give your body just enough carbs to support liver glycogen stores and fuel the brain and central nervous system at rest, have good cognitive function, energy, and mood, but without overshooting your daily needs and gaining fat.
I’ve consulted with a few corporate wellness programmes that have used this strategy to collectively achieve thousands of pounds of weight loss, and even more importantly, dramatic improvements in biomarkers of health. A plethora of research supports this approach. One study demonstrated that increasing the proportion of protein to carbohydrate in the diet of adult women has positive effects on body composition, blood lipids, glucose homeostasis and satiety during weight loss.
A meta-regression analysis showed that haemoglobin A1c, fasting glucose, and some lipid fractions (triglycerides) improved with lower carbohydrate diets. The overall effect on weight was equivocal amongst the studies evaluated in this research.
Those findings are interesting for the Average Joes who lead a predominately sedentary life, but what are the implications if you’re a fully signed up member of the Iron Game? The short summary is that anaerobic exercise, which includes strength training, cross training, HIIT and intermittent sprint sports, creates a unique metabolic environment, which changes the way your body processes macronutrients for 24-48 hours after the completion of such a session.
If you exercise three to five days per week, then your body is virtually in a recovery mode 100% of the time. You are in an altered physiological state permanently, therefore your nutritional needs are completely different to the average office worker. A good analogy is your car. If your car has been sitting in the garage it doesn’t need gas. Loading up on carbs is like trying to fill up a full tank. It just spills over the side. In the human body, this overspill equates to sugar backing up in the bloodstream, resulting in high blood-glucose levels. This in turn leads to body-fat storage and a host of other negative effects like elevated triglycerides and cholesterol, insulin resistance, and, eventually, type 2 diabetes.
However, if you drive your car around every day, sometimes for long mileage, you have to fill it up often. If you don’t you will run out of gas. An empty tank in the human body equates with fatigue, depression, lethargy, irritability, impaired performance, muscle loss, stubborn fat, insomnia, low testosterone, impaired thyroid production and resting metabolic rate, foul mood, and frustration that despite dieting and training hard your body stubbornly refuses to change.
The case for carbs
The primary goal for most competitive athletes is to perform at the highest level. Because carbohydrates are the fuel for high-intensity exercise, most sports nutrition diet plans focus on carbohydrates first. Most research focuses on the optimum amounts to keep liver and muscle glycogen at near full levels to maximise recovery and performance, both during training and during competition.
According to the NSCA, endurance athletes may need up to 10g of carbs per kilo of bodyweight to maximise glycogen stores. Strength training athletes may only need half that, so around 5g per kilo.
Recommendations developed on behalf of the International Olympic Committee suggest 5-7g of carbs per kilo during regular training, and between 7-10g per kilo during bouts of increased training, with a recovery period of no less than 24 hours for maximal glycogen restoration.
We know why an athlete or regular exerciser can handle more carbs than a sedentary person. But it’s also important to understand that the needs and goals of high-level performance athletes are different to those who are competing in the physique arena.
The training of performance-based athletes tends to be higher in duration and frequency: they may train two to four hours per day, sometimes twice a day, six days a week. A traditional hypertrophy routine may consist of three to five, 40-60 minute strength-training workouts per week.
So performance athletes obviously have much higher calorie and carbohydrate demands than Speedo-wearing stage dynamos. Besides, the goal of achieving high levels of performance is much different than losing maximum amounts of body fat. There can be overlap for sure, but there are also clear distinctions.
Eating 10g of carbs per kilo of bodyweight for a 90kg (198lbs) male equates to 900g of carbohydrate per day. For a 60kg (132lbs) female it’s 600g of carbs. While you might have a ton of energy and perform well with those numbers, most would have a very hard time getting lean on such a high intake of carbs.
The goal would be to move closer to the middle ground and provide just enough carbs to properly fuel and recover from strength training sessions without any excess being stored as body fat.
So, the big questions is, how do you get there? There is a wide range of appropriate carbohydrate intakes based on specific activity levels, individual metabolic factors, and body composition goals. A good ballpark starting point would be somewhere in the range of 2-5g of carbs per kilo of lean body mass or target weight.
Those with good insulin sensitivity, on the higher end of training intensity or volume, and/or looking to gain muscle mass would lean towards the higher end. Those with poor insulin sensitivity, on the lower end of training intensity or volume, and/or looking to lose fat would lean towards the lower end.
Ultimately, my advice for working out your own carb customisation strategy is to start with my suggestions based on your own unique profile and physical exertions. From there, as with any aspect of fitness, you need to monitor your progress and adapt based on how your body responds.
1 Layman, et al. A Reduced Ratio of Dietary Carbohydrate to Protein Improves Body Composition and Blood Lipid Profiles during Weight Loss in Adult Women. J. Nutr. February 1, 2003 vol. 133 no. 2 411-417
2 Kirk, et al. Restricted-carbohydrate diets in patients with type 2 diabetes: a meta-analysis. J Am Diet Assoc. 2008 Jan;108(1):91-100.
3 Burke, et al. Recommendations developed on behalf of the International Olympic Committee by experts in Sports Nutrition