The British Dietetic Association (BDA), the UK’s go-to pros for dietitians (https://www.bda.uk.com/), sorts carbs into three essential types: sugars, starches, and dietary fibre.

Table 1: Adapted from the BDA (2016)

Putting the fancy "saccharide" talk to one side, just remember: Simple carbs = fast fuel. Complex carbs = steady fuel.

How Your Body Turns Carbs Into Power.

So, you've eaten your carbs. What now? Your gut breaks most of them down into individual sugar units, which then hit your bloodstream as glucose.

• Simple carbs? They get absorbed fast, spiking your blood sugar quick. Perfect for immediate energy.
• Complex carbs? They take their sweet time, delivering a slower, more sustained rise in blood sugar. Ideal for longer-lasting power.

Once that glucose is in your bloodstream, it either powers your cells (muscles, brain) directly, or your body stores it as glycogen in your liver and muscles [1, 4]. Think of glycogen as your personal, ready-to-deploy fuel tanks.

Glycaemic Index (GI) & Glycaemic Load (GL): The Smarter Carb Tools.

The old "simple vs. complex" carb talk is fine, but for true performance, you need more. Enter the Glycaemic Index (GI). This measures how fast and how much a carb makes your blood sugar jump.

• High-GI foods (like white bread) send your blood sugar soaring quickly. Great for a rapid energy boost or reloading after a brutal session.
• Low-GI foods (slow-release carbs) deliver a gentle, steady rise. Good for sustained energy.

Here's the catch with GI; it measures foods based on 50g of carb content, not a typical serving. That's why even carrots can look "high GI" – because you'd need to eat an insane amount (like 700g!) for that effect.

That's where Glycaemic Load (GL) steps up. GL takes into account both GI and how much carb is in a real-world serving. So, those carrots? High GI, but a very low GL. Meaning you can enjoy them without worrying about a major blood sugar spike. It's about smart portions, not just raw numbers.

Carb Strategy for Elite Performance and for You!

The pros aren't arguing about "low carb" or "high carb" anymore. They're doing something smarter; carbohydrate periodisation, or "fuel for the work required."

Your muscles store carbs as glycogen. When you train hard, you burn through it. The tougher or longer the session, the more you torch. Sprints? Glycogen gone fast. Endurance grind? Slower burn, but still depletes [5].

The game-changer? Match your carb intake to your training. Light day? Less carbs needed. Heavy, intense, or long session? You'll need more to top up those fuel tanks.

What Does That Mean For Your Performance?

Serious athletes might need 8–12g of carbs per kilo of body weight to fully recover glycogen after intense, prolonged activity [2,3]. But here’s the reality: many active people aren't hitting those numbers.

Fall short on carbs, and you'll feel it:

• Capped performance in high-intensity and long workouts.
• Brain fog during those extended sessions.
• Crashed energy levels that leave you drained.

On rest or lighter days, dial back the carbs. It's about smart adjustments to match your output.

Five Common Carb Myths, Busted.

• "Carbs are Unhealthy." False. They're your primary energy source and many carb-rich foods pack vital fibre, vitamins, and minerals. Don't ditch them; choose wisely.
• "Eating Carbs Makes You Fat." Nope. Every gram of carb stores with water, so you might see a temporary weight bump (that's just water!). Carbs only add fat if you're consistently eating too many calories overall.
• "Low-Carb Diets are the Only Way to Lose Fat." Low-carb days can have their place for specific goals, but ultimate fat loss always boils down to a healthy calorie deficit. No magic bullet here.
• "Don't Eat Carbs Before Exercise." Training in a low-carb state can trigger cool physiological adaptations. But this is advanced stuff, only for controlled situations with pro guidance. Don't risk a bad session without proper support.
• "Carbs After 6pm Make You Fat." Your total daily calorie intake matters far more than when you eat your carbs. Period.

Your Key Takeaways.

• Carbs are your go-to fuel, classified as simple (fast) or complex (steady).
• Your body breaks them down into glucose for immediate use or stores them as glycogen.
• GI measures speed, GL measures impact – know the difference.
• Fuel for the work required: Match your carb intake to your training intensity and duration.
• Skimp on carbs, and your performance, focus, and energy will suffer.

There you have ’em. Carbohydrates…ready to power your next session.

References

1. Burke, Louise M.a; Hawley, John A.b. Carbohydrate and exercise. Current Opinion in Clinical Nutrition and Metabolic Care 2(6):p 515-520, November 1999. https://journals.lww.com/co-clinicalnutrition/abstract/1999/11000/carbohydrate_and_exercise.15.aspx

2. Nutrition and Athletic Performance. Medicine & Science in Sports & Exercise 48(3):p 543-568, March 2016. https://journals.lww.com/acsm-msse/fulltext/2016/03000/nutrition_and_athletic_performance.25.aspx

3. Louise M. Burke, Luc J. C. van Loon, and John A. Hawley Postexercise muscle glycogen resynthesis in humans Journal of Applied Physiology 2017 122:5, 1055-1067 https://journals.physiology.org/doi/epdf/10.1152/japplphysiol.00860.2016

4. Jeukendrup AE. Carbohydrate feeding during exercise. International Journal of Sports Medicine 1992; 13: S126-S128

5. Hargreaves, M., Hawley, J. A., & Jeukendrup, A. (2004). Pre-exercise carbohydrate and fat ingestion: effects on metabolism and performance. Journal of Sports Sciences, 22(1), 31–38. https://doi.org/10.1080/0264041031000140536