Carbohydrates and Training

Overview

Carbohydrate is the fuel that high intensity work runs on. The harder and more repeated the effort, the more it matters.

It is also the most demonised macronutrient of the last two decades, largely because cutting it produces fast initial weight loss that is mostly water.

Quick Answer

Carbohydrate is the main fuel for high intensity exercise. Most people who train need roughly 3 to 6 grams per kilogram of bodyweight per day, rising towards 6 to 10g per kg for endurance athletes training daily.

Key Points

Carbohydrate fuels high intensity work; fat fuels low intensity work.
Muscle glycogen is what runs out during hard sessions.
The initial weight drop on low carb is water, not fat.
Endurance athletes need substantially more than lifters.
Low carb training is possible but usually costs performance in hard sessions.

How much you need

Training type	Carbohydrate per kg bodyweight
Mostly sedentary	2 to 3g
Resistance training 3 to 4 days a week	3 to 5g
Hard training most days	5 to 7g
Endurance training, high volume	6 to 10g

For an 80kg lifter training four times a week, 240 to 400g per day is a sensible band. In a calorie deficit that comes down, because carbohydrate is the flexible macro once protein and minimum fat are set.

Glycogen, in plain terms

Carbohydrate is stored in muscle and liver as glycogen. A trained adult holds roughly 400 to 500g in total, of which about 80 percent sits in muscle.

Each gram of glycogen is stored with around 3 grams of water. That is why:

-Cutting carbohydrate hard drops 1 to 2kg of scale weight within days.
-Reintroducing carbohydrate puts it straight back.
-Neither event tells you anything about body fat.

Glycogen also explains the pump and the fuller look after a high carbohydrate day.

When carbohydrate matters most

Session type	Carbohydrate importance
Heavy singles and triples	Moderate
High volume hypertrophy work	High
Intervals and repeated sprints	Very high
Long steady cardio	High for duration, moderate for intensity
Low intensity walking	Low

The sessions where carbohydrate availability makes an obvious difference are the long, repeated, high effort ones. A five rep set of squats is not glycogen-limited. Twenty sets across ninety minutes is closer to it.

Around your session

Timing	Practical guidance
2 to 3 hours before	A normal mixed meal with carbohydrate
30 to 60 minutes before	Something easy to digest, if you want it
During	Only relevant beyond about 90 minutes of hard work
After	Part of your next normal meal is sufficient

For a typical hour-long gym session in someone eating adequate carbohydrate daily, intra-workout fuelling is unnecessary.

Low carbohydrate approaches

Low carbohydrate and ketogenic diets can produce fat loss, because they produce a calorie deficit. They also tend to reduce performance in high intensity and repeated effort work, at least for the first several weeks and often beyond.

If you enjoy eating that way and your training is mostly low intensity, it is a reasonable choice. If your training is hard and repeated, you are choosing a handicap.

Common Mistakes

Mistake	Why it causes problems	Better approach
Cutting carbohydrate to near zero while training hard	Performance falls, sessions get worse	Keep enough to fuel key sessions
Reading the water drop as fat loss	Sets false expectations	Judge over weeks, not days
Carb loading before a normal gym session	Unnecessary for an hour of lifting	Save it for genuine endurance events
Avoiding fruit for its sugar	Removes fibre and micronutrients for no benefit	Fruit is fine
All carbohydrate from refined sources	Poor fibre and satiety	Mostly whole grains, fruit, vegetables, legumes

Frequently Asked Questions

Do I need carbs to build muscle?

Not strictly, but they help. Adequate carbohydrate supports training quality and spares protein from being used for energy, both of which support muscle gain indirectly.

Are carbs bad at night?

No. Total daily intake determines body composition. Meal timing has a small effect on performance and essentially none on fat gain.

Should I cycle my carbs?

Carb cycling, eating more on hard training days, is a reasonable refinement if you already track consistently. It is not necessary for good results.

What are the best carbohydrate sources?

Mostly whole sources: oats, rice, potatoes, pasta, bread, fruit, legumes. More refined sources around training are fine and often easier to digest.