Carbohydrates
Carbohydrates are the sugars, starches and fibre in plant foods and milk. They're your body's preferred fuel for hard training, and your brain's main fuel.
On this page
Why carbs matter
- Fuel for hard work. Muscles store carbohydrate as glycogen and burn it fastest during heavy sets, sprints and intervals.
- Fuel for your brain. Your brain alone uses around 100–120 g of glucose a day1.
- Spare your protein. With enough carbs, protein can go into repair instead of being burned for energy.
- Bring fibre with them. Wholegrains, fruit, vegetables and beans are where most of your fibre comes from.
Carbohydrate has 4 kcal per gram. UK food labels list fibre separately, so the carbohydrate figure on a label doesn't include it.
Simple vs complex carbs
| Simple carbs (sugars) | Complex carbs (starches and fibre) | |
|---|---|---|
| What they are | One or two sugar units: glucose, fructose, sucrose (table sugar), lactose (milk sugar) | Long chains of sugar units: starch, and fibre that you can't digest |
| Found in | Fruit, milk, honey, sugar, syrups, sweets, fizzy drinks | Oats, bread, rice, pasta, potatoes, beans, lentils |
| How fast | Usually absorbed quickly | Absorbed more slowly, especially when wholegrain and high in fibre |
The split isn't the whole story. Whole fruit is "simple" but comes packed with fibre, water and vitamins, while white bread is "complex" and digests almost as fast as sugar. It's more useful to ask how processed a carb is and how much fibre comes with it. Glycaemic index measures how fast it raises blood sugar.
How many carbs you need
| Who | Guideline |
|---|---|
| Most adults (UK)2 | About half your daily calories from carbohydrate, mostly starchy, high-fibre foods |
| Strength training most days4 | About 4–7 g per kg of body weight a day |
| Moderate exercise, about an hour a day5 | 5–7 g per kg a day |
| Free sugars (everyone)2 | Under 5% of calories: no more than 30 g a day |
Lifters don't need as many carbs as endurance athletes, but training on very low carbs tends to hurt volume and performance. Around your sessions is the best place to put them: see Pre- and post-workout nutrition.
Best carbohydrate sources
| Food | Per 100 g | Per serving |
|---|---|---|
| Oats, dry | 60 g | 24 g40 g |
| Wholemeal bread | 41 g | 32.8 g2 slices (80 g) |
| White rice, boiled | 28 g | 50.4 g180 g |
| Wholewheat pasta, boiled | 24 g | 43.2 g180 g |
| Brown rice, boiled | 22 g | 39.6 g180 g |
| Banana | 20 g | 24 g1 medium (120 g) |
| Potatoes, boiled | 17 g | 34 g200 g |
| Sweet potato, baked | 17 g | 25.5 g1 medium (150 g) |
| Kidney beans, canned, drained | 13 g | 15.6 g120 g |
| Lentils, boiled | 12 g | 18 g150 g |
| Apple | 11.5 g | 17.2 g1 medium (150 g) |
Aim for most of your carbs to come from wholegrains, potatoes with the skin on, beans, fruit and vegetables. They bring fibre, vitamins and minerals that sugary foods don't.
Common myths
MythCarbs make you fat.
FactEating more calories than you burn does, whatever they come from. In a year-long trial of 609 adults, healthy low-carb and healthy low-fat diets led to about the same weight loss89.
MythDon't eat carbs after 6pm.
FactThe clock doesn't decide whether carbs are stored as fat; your total intake over days and weeks does. See The best time to eat.
MythFruit is too sugary to eat on a diet.
FactSugar in whole fruit isn't a free sugar. Fruit is filling and low in calories for its size. Juice and smoothies are the ones to keep to 150 ml a day.
Track this in NutriLog
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References
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. The National Academies Press, Washington, DC, 2005. doi:10.17226/10490
- Scientific Advisory Committee on Nutrition. Carbohydrates and Health. The Stationery Office, 2015.
- NHS. Sugar: the facts. nhs.uk.
- Slater G, Phillips SM. Nutrition guidelines for strength sports: sprinting, weightlifting, throwing events, and bodybuilding. J Sports Sci. 2011;29 Suppl 1:S67-S77. doi:10.1080/02640414.2011.574722
- Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement: Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016;48(3):543-568. doi:10.1249/MSS.0000000000000852
- Public Health England. McCance and Widdowson's The Composition of Foods Integrated Dataset (CoFID). GOV.UK, 2021.
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central. fdc.nal.usda.gov.
- Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype or insulin secretion: the DIETFITS randomized clinical trial. JAMA. 2018;319(7):667-679. doi:10.1001/jama.2018.0245
- Hall KD, Guo J. Obesity energetics: body weight regulation and the effects of diet composition. Gastroenterology. 2017;152(7):1718-1727.e3. doi:10.1053/j.gastro.2017.01.052