Carbohydrates: how much do you need?
Carbohydrates can be confusing: one moment you hear that you don’t need them at all, and the next that your workouts will go nowhere without them. The simple truth is that your needs depend on whether you spend most of the day sitting, do strength training or are preparing for a long endurance workout.
This article explores a practical range, looking at ketosis, the impact of training, and the lower and upper limits. A slow-carb diet can be one way to bring structure to your eating, but your intake still needs to suit you, your training load and your goals.
Carbohydrates and ketosis: why does it matter?
Ketosis is often discussed as though it were either a miracle or a danger. The reality is simpler. When carbohydrate intake is severely restricted and your body uses large amounts of fatty acids, your liver starts producing ketone bodies. Many cells and tissues can use these for energy when carbohydrates are scarce.
Nutritional ketosis is not the same as diabetic ketoacidosis. It is your body’s way of adapting to a limited supply of a particular nutrient. Many very low-carbohydrate diets, such as the Atkins diet, are based on ketosis. Stricter ketogenic diets keep carbohydrate intake at around 30 g per day, and even low-calorie vegetables often supply that amount.
This is where the friction starts. Some keto advocates will argue over an intake even slightly above that level. In practice, any diet with less than 100 grams of carbohydrates per day causes some degree of ketosis. The lower the intake, the more ketone bodies are usually produced.
Ketostix test strips, which indicate ketone levels in urine, have often been used to gauge the depth of ketosis. They do not always give an accurate picture. The amount of ketone bodies in your urine may not reflect what is actually happening in your body.
At 15 – 20 grams of carbohydrates per day, ketosis is virtually guaranteed. However, an intake this low may not always be enough to spare your body’s proteins. Dietary variety also quickly suffers. Frankly, this is too restrictive for many people.
Your body’s absolute physiological requirement for carbohydrates may be 0 grams per day. The practical question, however, is different: how much do you need to feel well and spare your body’s proteins, including muscle mass? If you do not exercise and lead a fairly inactive life, 50 grams per day can be considered a practical minimum. This assumes that your diet provides enough protein.
Translator’s note: I want to stress here that this 50 grams clearly applies when you are not exercising and are simply going about an ordinary, inactive life.
Ketosis does not suit everyone. Some people become sluggish, struggle to think clearly and feel awful. Sometimes even several weeks of adaptation do not help. If your body is clearly telling you that this way of eating does not suit you, there is little sense in stubbornly sticking with it.
Translator’s note: it is also likely to be a poor fit for the dieter’s individual metabolism and circumstances.
Tolerance is also linked to insulin sensitivity. People with good insulin sensitivity often tolerate higher-carbohydrate diets better and very low-carbohydrate diets less well. Those with lower insulin sensitivity sometimes do better with a lower carbohydrate intake. There is also a third group: metabolically flexible people who can adapt to either approach. The original author referred here to his article “Insulin Sensitivity and Fat Loss”.
Carbohydrates when you train
If your goal is to avoid ketosis and your physical activity is minimal or nonexistent, 100 – 120 grams of carbohydrates per day should usually be enough. This amount supports normal functioning but does not cover the demands of serious, intense training. Training uses up a large share of it.
Without substantial training, the practical range is therefore around 50 – 120 grams per day. The lower end suits those who tolerate ketosis. The upper end suits those who do not, or who want to avoid it. These figures are not set in stone; they help you gauge where your minimum might lie.
Body size does not affect this minimum as much as you might expect. Much of this comes down to the brain’s needs, and brain mass does not increase in proportion to body weight. A woman weighing 60 kg and a man weighing 100 kg may therefore have quite similar physiological carbohydrate needs in practice.
Training changes the picture. Low-intensity aerobic activity, such as easy jogging or walking 3 – 5 times a week, does not increase carbohydrate needs very much. In that case, the same practical minimum is often enough.
Strength training also requires fewer carbohydrates than is often assumed. According to the original calculation, every 2 working sets use around 5 grams of carbohydrates, provided each set lasts 30 – 45 seconds. If your workout includes 24 working sets, you need around 60 additional grams of carbohydrates to replenish the glycogen used.
If your daily minimum was 50 grams and you add one day of strength training with 24 sets, that brings you to around 110 grams of carbohydrates. If your starting point is 100 – 120 grams, a solid strength workout of 24 sets may bring your daily intake to 160 – 180 grams. For a typical male gym-goer, this often means a maximum of 2 g/kg of body weight.
Based on experience, bodybuilders have recommended 2 – 2.2 g/kg of body weight during fat loss phases and 6 – 6.5 g/kg of body weight during mass gain phases. This range of 2.2 – 6.5 g/kg is fairly close to the 5 – 7 g/kg range found in nutrition guidelines, especially when the aim is to support strength sports or higher training volumes.
Translator’s note: I certainly take issue with the author’s recommendation of “about 5 grams for every two working sets” completely ignoring the type of exercise involved. A 45-second set of squats and a 45-second set of barbell biceps curls cannot possibly have the same energy cost!
How much should you choose?
For high-intensity endurance training, the range is much wider. A sprinter running 60-meter intervals does not need huge amounts of carbohydrates each day. An endurance athlete training close to the anaerobic threshold, however, can deplete their stores in 1 – 2 hours.
Even lower-intensity workouts can deplete carbohydrate stores in both the muscles and the liver if they last a very long time, such as 2 – 6 hours. For an athlete training intensely, full depletion can mean using at least 300 – 400 grams of carbohydrates. For an endurance athlete of average body weight, this can mean as much as 6g/kg or even more.
Endurance athletes who train seriously are often advised to consume 7 – 10 g/kg, but several studies have shown that many endurance athletes consume an average of up to 5 g/kg. These are people who train at high volumes and intensities every day. Recreational athletes usually need nowhere near this amount.
These recommendations assume that the goal is to maintain or restore muscle carbohydrate levels. During fat loss, you may need to accept lower levels. This does not automatically mean better results, just a different goal: a lower energy intake and greater control over how much you consume.
Sometimes the goal is to increase glycogen stores through carbohydrate loading. This involves eating more for a period of time than you would normally need to maintain those stores. Endurance athletes sometimes do this to improve performance.
The theoretical upper limit would be a situation in which carbohydrates provide 100% of your daily calorie intake. An average man’s daily calorie intake might be 31 – 35 kcal/kg. Since carbohydrates provide 4 kcal per gram, this would mean 8.8 g/kg in this example. But that would leave no room for protein or fat, which is not sensible.
Very large amounts have also been used after muscle carbohydrate stores have been depleted. Intakes of up to 16 g/kg over a 24-hour period have been achieved without adverse effects. This is probably among the highest amounts used in practice, but it is a special case, not a routine dietary recommendation.
Carbohydrates: a practical summary
Carbohydrate needs can vary enormously. For the same 73 kg man, the range can extend from 0 grams to 1170 grams per day. No wonder people are confused.
If you do not work out, 50 grams may be a practical lower limit, provided ketosis suits you and you get enough protein. If you want to avoid ketosis, 100 – 120 grams is a more sensible starting point. If you do strength training, factor in your training volume. If you do long or intense endurance workouts, your needs rise quickly.
A diet based on slow-digesting carbohydrates may help keep your blood sugar and appetite more stable, but it does not make the math disappear. Potatoes, buckwheat, rolled oats, rice and vegetables can all fit into your diet. What matters is the amount, the timing and what your body actually tolerates.
Related articles:
How many carbohydrates do we actually need… Part I
How many carbohydrates do we actually need… Part II
FAQ
Are carbohydrates essential for the body?
The absolute physiological requirement may be 0 grams per day because the body can also use other energy sources. In practice, the picture is different: well-being, training, maintaining muscle mass and dietary variety make some carbohydrate intake beneficial for most people.
Is ketosis suitable for everyone?
No. Some people feel good, while others become sluggish and cannot train normally. If you still feel unwell after the adaptation period, there is no need to force yourself to continue a low-carbohydrate diet.
How many carbohydrates should you eat on a strength training day?
It depends on your training volume. The original simple estimate suggested about 5 grams for every 2 working sets, but the difficulty and duration of the exercise change the picture. A substantial leg or back workout is not the same as a short arm workout.
Author: Janar Rückenberg (translation)
Source:Turg.Fitness.ee
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