Suggs Gym | Member Education
Nutrition Fundamentals:
Protein, Carbohydrate, Fat, Fibre and Minerals -
How to use this guide
This guide explains the building blocks of food: what each nutrient is, what it does in your body, how much you need, and where to find it. Understanding the “why” makes the “what to eat” far easier, and it helps you judge the nutrition claims you see online.
All figures are for healthy adults and follow UK guidance (SACN, the Eatwell Guide, UK Dietary Reference Values) alongside sports nutrition position stands (ISSN, ACSM). Needs vary with age, body size, training load, health conditions and medication, so treat these as starting points and talk to your coach for personal targets. If you have a medical condition, are pregnant, or take regular medication, speak to your GP or a registered dietitian before making big changes.
1. The big picture: macronutrients and micronutrients
Food supplies two broad groups of nutrients.
Macronutrients are needed in large amounts (grams per day) and provide energy: protein, carbohydrate and fat. Fibre is a type of carbohydrate that we treat separately because of its unique roles. Alcohol also provides energy but is not a nutrient we need.
Micronutrients are needed in small amounts (milligrams or micrograms) and do not provide energy, but your body cannot function without them. They are the vitamins and the minerals.
Energy in food
Energy is measured in kilocalories (kcal), often just called “calories”. On UK food labels the energy values used are approximately:
Nutrient Energy per gram
Fat 9 kcal (37 kJ)
Alcohol 7 kcal (29 kJ)
Protein 4 kcal (17 kJ)
Carbohydrate 4 kcal (17 kJ)
Fibre about 2 kcal (8 kJ)
Fat is the most energy-dense, which is why small changes in oils, spreads and fatty foods can have a big effect on total calories. Your total energy intake compared with what you burn (energy balance) determines whether you maintain, lose or gain weight. The split of macronutrients then influences body composition, performance, appetite and health.
2. Protein
What it is...
Proteins are long chains of smaller units called amino acids. Your body uses around 20 amino acids to build thousands of different proteins. The sequence and shape of each protein decides its job.
Essential amino acids cannot be made by the body and must come from food. There are nine: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. The rest are “non-essential”, which means the body can make them, not that they are unimportant.
What it does
• Builds and repairs tissue: muscle, tendon, ligament, bone matrix, skin, hair and nails all rely on protein.
• Makes enzymes and hormones: many enzymes that run your metabolism and hormones such as insulin are proteins.
• Supports immunity: antibodies are proteins.
• Transports and stores things: haemoglobin carries oxygen in your blood; other proteins carry fats, iron and vitamins.
• Maintains fluid balance and pH in the blood.
• Provides energy (4 kcal/g) when carbohydrate and fat are not sufficient, though this is not its preferred role.
Muscle protein turnover
Muscle is constantly being broken down and rebuilt. When muscle protein synthesis (building) exceeds muscle protein breakdown, you gain or maintain muscle. Two things switch synthesis on: resistance training and eating protein. Together they are more powerful than either alone. Protein eaten in a meal raises amino acid levels in the blood, and the amino acid leucine in particular acts as a trigger for muscle building. Roughly 2 to 3 g of leucine per meal is a useful target, which is usually met by a serving of 25 to 40 g of good-quality protein.
Protein quality: complete and incomplete proteins
A complete protein contains all nine essential amino acids in useful amounts. Animal foods (meat, fish, eggs, dairy) and some plant foods (soy, quinoa) are complete. Many plant proteins are lower in one or more essential amino acids; for example cereals are lower in lysine and pulses are lower in methionine. This is easily solved by eating a variety of plant proteins across the day (for example beans with rice or wheat, hummus with bread). They do not need to be combined in the same meal.
Quality is also affected by digestibility. Scientists measure this using scores such as PDCAAS and the newer DIAAS. Animal proteins and soy score highest; most other plant proteins score lower, so vegans and vegetarians may benefit from aiming for the upper end of the ranges below and including soy, pulses and mixed sources.
How much do you need?
• Population minimum: the UK Reference Nutrient Intake is 0.75 g per kg of body weight per day for adults. This is the amount to prevent deficiency in the general population, not an optimal amount for training.
• Active people and those training for strength or muscle: around 1.4 to 2.0 g per kg per day is supported by research, and some people in a calorie deficit or at higher training loads benefit from up to about 2.2 g per kg. A good gauge is 1.8-2.0g per day.
• Older adults (65+): about 1.0 to 1.2 g per kg or more, because muscle becomes less responsive to protein with age.
• Spread it out: about 0.25 to 0.4 g per kg per meal (roughly 20 to 40 g for most people) across three to five eating occasions gives the best muscle-building response. A larger portion at one meal is not harmful; it is just not used as efficiently for muscle building.
Example: an 80 kg member aiming for 1.6 g/kg needs about 128 g of protein a day, which might be four meals of about 30 to 35 g each.
Good sources (approximate protein)
Food Portion Protein
Chicken breast, cooked 100 g 30 g
Salmon fillet, cooked 100 g 22 to 25 g
Eggs 2 large 12 to 13 g
Greek yoghurt, plain 200 g 18 to 20 g
Cottage cheese 100 g 11 to 12 g
Tofu, firm 150 g 15 to 20 g
Lentils, cooked 150 g 12 to 14 g
Whey protein powder 1 scoop (30 g) 20 to 25 g
Values vary by brand and cooking method; check labels.
Common questions
• Is high protein bad for your kidneys? In people with healthy kidneys there is no good evidence that higher intakes within the ranges above cause harm. People with existing kidney disease must follow medical advice.
• Do I need supplements? No. Powders are a convenient way to reach your target, not a requirement. Food first, supplements to fill gaps.
• Does protein help fat loss? Yes, indirectly. It is the most filling macronutrient, has the highest thermic effect (your body uses roughly 20 to 30% of protein calories digesting it), and helps preserve muscle in a calorie deficit.
3. Carbohydrate
What it is...
Carbohydrates are compounds of carbon, hydrogen and oxygen. They are classed by the size of the molecule.
• Monosaccharides (single sugars): glucose, fructose, galactose.
• Disaccharides (double sugars): sucrose (table sugar: glucose and fructose), lactose (milk sugar: glucose and galactose), maltose.
• Polysaccharides (long chains): starch (digestible, found in grains, potatoes, pulses) and fibre (largely indigestible, see section 5).
When you digest starch and sugars, they are broken down to glucose and absorbed into the blood.
What it does
• Primary fuel for high-intensity exercise. Carbohydrate can be broken down quickly, with or without oxygen, so it powers sprints, lifting, intervals and hard endurance work.
• Fuel for the brain and nervous system. The brain uses around 120 g of glucose a day. When carbohydrate is very low it can use ketones, but glucose remains important.
• Stored as glycogen. Glycogen is the storage form of carbohydrate, held in muscle (about 300 to 500 g in total, depending on size and training) and in the liver (about 80 to 100 g). Muscle glycogen fuels the muscle it is stored in. Liver glycogen keeps blood glucose stable between meals. Each gram of glycogen is stored with around 3 g of water, which is why scale weight can change quickly when you change carbohydrate intake.
• Spares protein. When carbohydrate is available, the body is less likely to break down protein for energy.
Types of carbohydrate food
Starchy carbohydrates form the base of the UK Eatwell Guide, which suggests they make up just over a third of the diet, choosing higher-fibre or wholegrain options where possible: oats, wholemeal bread, brown rice, wholewheat pasta, potatoes with skins, beans and lentils.
Naturally occurring sugars in whole fruit, vegetables and plain milk come packaged with fibre, water, vitamins and minerals, and are digested more slowly.
Free sugars are sugars added to foods and drinks, plus sugars in honey, syrups and fruit juices and smoothies. UK guidance (SACN) recommends free sugars provide no more than 5% of total energy, about 30 g (roughly 7 teaspoons) a day for adults. Free sugars are linked to tooth decay and, when they displace more nutritious food or push calories too high, to weight gain.
Glycaemic index and glycaemic load
The glycaemic index (GI) ranks foods by how quickly they raise blood glucose compared with pure glucose. Low-GI foods (most pulses, oats, many fruits) cause a slower, smaller rise; high-GI foods (white bread, white rice, sports drinks) cause a faster, larger one. GI is influenced by processing, cooking, ripeness and what you eat with the food. The glycaemic load also considers portion size.
For general health, choosing mostly lower-GI, high-fibre carbohydrates is sensible. Around training, high-GI options are useful on purpose because they digest and absorb quickly.
How much do you need?
UK dietary guidance suggests around 50% of food energy from carbohydrate for the general population. Athletes and active people should scale carbohydrate to the demands of training. Sports nutrition guidelines suggest approximate daily ranges:
Training load Carbohydrate per kg body weight per day
Light (low intensity or skills sessions) 3 to 5 g
Moderate (around 1 hour a day) 5 to 7 g
High (endurance training 1 to 3 hours a day) 6 to 10 g
Very high (more than 4 to 5 hours a day) 8 to 12 g
Most members training 3 to 5 times a week with strength and conditioning work will sit around 3 to 6 g per kg, adjusting up on heavy or long days and down on rest days.
Carbohydrate around training
• Before: a meal containing carbohydrate and some protein 2 to 4 hours before, or a small carbohydrate snack 30 to 60 minutes before, helps top up fuel.
• During: for sessions under about 60 minutes, water is usually enough. For 1 to 2.5 hours, aim for roughly 30 to 60 g of carbohydrate per hour. For longer or very hard efforts, up to 90 g per hour is used by trained endurance athletes, using a mix of glucose and fructose to maximise absorption. Train your gut with practice in training.
• After: if you will train again within about 8 hours, take around 1.0 to 1.2 g per kg per hour for the first few hours alongside protein to speed glycogen refuelling. If you have 24 hours or more, normal meals will restore glycogen.
Low-carbohydrate diets
Very low-carbohydrate and ketogenic diets can work for weight loss and some medical purposes, but they usually reduce capacity for high-intensity training. Carbohydrate is not essential in the strict sense (the body can make glucose from protein and fat), but there is little reason to avoid it for most active people, and carbohydrate-rich foods supply fibre and micronutrients.
4. Fats
What they are...
Fats (lipids) are made mostly of triglycerides: a glycerol backbone with three fatty acids attached. The type of fatty acid determines how the fat behaves in food and in the body. Fats are not just stored energy; they are essential.
What they do...
• Energy: the most concentrated source at 9 kcal/g, and the main fuel at rest and during low-to-moderate exercise. Even lean people store tens of thousands of kilocalories as body fat.
• Cell membranes: every cell in the body is wrapped in a fat-based membrane.
• Hormones: cholesterol is the raw material for steroid hormones including testosterone, oestrogen, progesterone and cortisol, and for vitamin D. Very low-fat diets and very low body fat can disrupt hormones.
• Absorbing fat-soluble vitamins: vitamins A, D, E and K need fat to be absorbed.
• Brain and nerves: the brain is about 60% fat by dry weight, and nerves are insulated by fat-rich myelin.
• Protection and insulation for organs and body temperature.
• Taste, texture and satiety.
Types of fat
Saturated fat has no double bonds, and tends to be solid at room temperature. It is found in fatty meat, butter, cheese, cream, lard, coconut oil, palm oil, and many pastries and biscuits. A high intake raises LDL (“bad”) cholesterol, which is linked to cardiovascular disease. UK guidance is for saturates to provide no more than about 11% of food energy, roughly 30 g a day for men and 20 g for women.
Unsaturated fat has one or more double bonds and is usually liquid at room temperature.
• Monounsaturated fat (olive oil, rapeseed oil, avocado, many nuts) helps maintain healthy cholesterol when it replaces saturated fat.
• Polyunsaturated fat includes the two essential fatty acids:
– Omega-6 (linoleic acid): sunflower, corn and soya oils, many nuts and seeds.
– Omega-3 (alpha-linolenic acid, ALA): flaxseed, chia, walnuts, rapeseed oil. The body converts a small fraction of ALA to EPA and DHA, the long-chain omega-3s found directly in oily fish (salmon, mackerel, sardines, herring, trout) and algae oil. EPA and DHA support heart, brain, eye and possibly joint and recovery health.
Trans fats are produced by industrial hydrogenation (and occur naturally in small amounts in dairy and meat). Industrial trans fats raise LDL and lower HDL and are the most harmful type. Intakes in the UK are now low; keep them as low as possible, and certainly under 2% of food energy.
Essential fatty acids
Linoleic acid (omega-6) and alpha-linolenic acid (omega-3) cannot be made by the body and must be eaten. Deficiency is rare in people with normal diets.
How much do you need?
• UK guidance suggests total fat should provide no more than about 35% of food energy, with most coming from unsaturated sources.
• For athletes, around 20 to 35% of energy from fat is typical, with about 0.5 to 1.5 g per kg of body weight a day often used. Going below roughly 20% for long periods may compromise hormone function and fat-soluble vitamin intake.
• Oily fish: aim for at least two portions of fish a week, one of them oily (a portion is about 140 g cooked).
• Practical swaps: replace some butter, lard, fatty meat and pastries with olive or rapeseed oil, nuts, seeds, avocado and fish.
Cholesterol
Cholesterol is a fat-like substance made mostly by your liver. For most people, the saturated fat you eat influences blood cholesterol more than the cholesterol in food. Eggs and shellfish are fine for most people as part of a balanced diet. People with high cholesterol or a family history should follow their doctor’s advice.
A note on fat and exercise
Trained people burn more fat at a given intensity, but fat cannot supply energy fast enough for sprinting or heavy lifting. You do not need to “eat fat to burn fat”; body fat is lost through an overall calorie deficit.
5. Fibre
What it is...
Fibre is the part of plant foods that your small intestine cannot digest. It is a carbohydrate (or carbohydrate-like substance) that passes to the large bowel, where it is either fermented by gut bacteria or adds bulk. Fibre is only found in plant foods; there is none in meat, fish, eggs or dairy.
Fibre is often split into two types, though most plant foods contain both.
• Soluble (and viscous) fibre dissolves or swells in water to form a gel. Examples: beta-glucan in oats and barley, pectin in apples and citrus, and the fibre in pulses. It slows digestion, helps lower LDL cholesterol and moderates blood glucose.
• Insoluble fibre does not dissolve. Examples: wheat bran, wholegrain cereals, skins of fruit and vegetables, nuts and seeds. It adds bulk and speeds the passage of food, helping to prevent constipation.
Resistant starch (in cooked-and-cooled potatoes, rice or pasta, under-ripe bananas and pulses) behaves like fibre and feeds beneficial gut bacteria.
What it does
• Bowel health: softens and bulks stools and reduces constipation; a high-fibre diet is linked to lower risk of bowel cancer and diverticular disease.
• Feeds the gut microbiome: bacteria ferment fibre to produce short-chain fatty acids (such as butyrate), which nourish the cells lining the bowel and have anti-inflammatory effects.
• Heart health: soluble fibre helps reduce LDL cholesterol.
• Blood glucose control: slows absorption of sugar, lowering the risk of type 2 diabetes.
• Fullness and weight management: high-fibre foods are filling and often lower in energy density.
How much do you need?
The UK recommendation (SACN, 2015) is 30 g a day for adults (and 16- to 18-year-olds). Children need less: about 15 g for ages 2 to 5, 20 g for 5 to 11, and 25 g for 11 to 16. Most UK adults eat only about 18 to 20 g a day.
Easy ways to reach 30 g
• Choose wholegrain or higher-fibre bread, cereals, pasta and rice.
• Make oats, wholegrain cereal or fruit part of breakfast.
• Add beans, lentils or chickpeas to stews, soups, salads and chilli.
• Eat at least five portions of fruit and vegetables a day (80 g each), keeping skins on when you can.
• Snack on fruit, raw vegetables, nuts, seeds or popcorn.
Practical tips
• Increase gradually over a couple of weeks to avoid bloating and wind.
• Drink enough fluid. Fibre absorbs water; without enough fluid it can worsen constipation.
• Around hard training or races, some athletes reduce very high-fibre foods in the hours before to limit stomach upset. Practise in training.
• Fibre can slightly reduce the absorption of some minerals if intake is extreme, which is not a concern with a normal mixed diet.
6. Minerals
What they are...
Minerals are inorganic elements that the body cannot make. They come from soil and water, taken up by plants and then by animals. They are involved in building bone, nerve and muscle function, fluid balance, oxygen transport, energy production, immunity and hormone production.
Minerals are divided by how much we need.
• Macrominerals (major): needed in amounts of hundreds of milligrams a day or more: calcium, phosphorus, magnesium, sodium, potassium, chloride and sulphur.
• Trace minerals: needed in small amounts (milligrams or micrograms): iron, zinc, iodine, selenium, copper, manganese, fluoride, chromium and molybdenum.
Minerals compete for absorption and too much of one can reduce another, so supplements should be used with care. A varied diet usually meets needs, and minerals should not be supplemented without a reason (a blood test, medical advice or a clear dietary gap).
The figures below are UK Reference Nutrient Intakes (RNIs) for adults aged 19 to 50 unless stated.
Calcium (RNI 700 mg a day)
• Roles: about 99% is in bones and teeth; also essential for muscle contraction, nerve signalling, blood clotting and enzyme function.
• Sources: milk, yoghurt, cheese, calcium-fortified plant milks and tofu, tinned fish with bones (sardines), kale, broccoli, almonds.
• Notes: peak bone mass is reached around 30, so bone health in your teens and twenties matters for life. Vitamin D is needed for absorption. In the UK, everyone is advised to consider 10 micrograms of vitamin D daily in autumn and winter because sunlight is too weak. Low energy intake in athletes can harm bone health. Weight-bearing and resistance exercise strengthen bone.
Phosphorus (RNI 550 mg a day)
• Roles: bone and teeth structure, ATP (the cell’s energy currency), cell membranes, DNA.
• Sources: meat, fish, dairy, eggs, nuts, pulses, wholegrains. Deficiency is rare.
Magnesium (RNI 300 mg men, 270 mg women)
• Roles: cofactor in over 300 enzyme reactions, including energy production and protein synthesis; muscle and nerve function; bone health.
• Sources: nuts, seeds, wholegrains, leafy greens, pulses, dark chocolate.
• Notes: many UK adults fall short. Very high supplemental doses can cause diarrhoea. Supplementing is usually not needed for muscle cramps without evidence of deficiency.
Sodium and chloride (together: salt)
• Roles: fluid balance, blood volume and pressure, nerve impulses, muscle contraction, nutrient absorption. Sodium is the main mineral lost in sweat.
• Guidance: adults should eat no more than 6 g of salt a day (about 2.4 g sodium). Most UK adults eat more, mainly from bread, processed meat, sauces, ready meals and snacks. High intake raises blood pressure.
• Athletes: heavy sweaters in long events or hot conditions may need extra sodium during and after exercise, especially when drinking large volumes of water. Most gym sessions do not require special salt supplementation.
Potassium (RNI 3,500 mg a day)
• Roles: fluid balance, nerve signals, muscle contraction and heart rhythm; helps offset the blood-pressure effect of sodium.
• Sources: potatoes, bananas, beans, lentils, spinach, tomatoes, oranges, avocado, yoghurt, fish.
• Notes: most people who eat enough fruit, vegetables and pulses meet this. People with kidney disease or taking certain blood pressure medicines must be careful and follow medical advice.
Iron (RNI 8.7 mg men and women over 50; 14.8 mg women aged 19 to 50)
• Roles: part of haemoglobin (carries oxygen in blood) and myoglobin (in muscle); needed for energy production and immunity.
• Sources:
– Haem iron (meat, especially red meat and liver, and fish) is well absorbed.
– Non-haem iron (pulses, dark green vegetables, fortified cereals, nuts, seeds, wholegrains, dried apricots) is less well absorbed.
• Absorption tips: vitamin C eaten with the meal boosts non-haem iron absorption. Tea, coffee, calcium and high-phytate foods reduce it, so avoid drinking tea or coffee right at the meal.
• At higher risk of low iron: women with heavy periods, vegetarians and vegans, endurance athletes (through sweat, gut and foot-strike losses, and training effects on iron regulation), teenagers in growth spurts and frequent blood donors.
• Notes: persistent fatigue, breathlessness, pale skin or poor performance can be signs of iron deficiency, but they have many causes. Get a blood test before taking iron supplements. Too much iron is harmful and can cause constipation and, in high doses, serious toxicity.
Zinc (RNI 9.5 mg men, 7 mg women)
• Roles: immune function, wound healing, protein and DNA synthesis, growth, taste and smell, and testosterone and other hormone production.
• Sources: meat, shellfish (especially oysters), dairy, eggs, pulses, nuts, seeds, wholegrains.
• Notes: plant sources are less well absorbed because of phytates, so vegetarians and vegans may need slightly more. Long-term high supplemental intakes (above about 25 mg a day) can cause copper deficiency.
Iodine (RNI 140 micrograms a day)
• Roles: an essential part of thyroid hormones, which control metabolic rate, growth and development.
• Sources: milk and dairy, white fish and shellfish, eggs. Seaweed varies widely and can contain very high amounts, so limit kelp.
• Notes: most plant-based milk alternatives are not fortified with iodine unless stated on the label, so people who avoid dairy and fish may fall short.
Selenium (RNI 75 micrograms men, 60 micrograms women)
• Roles: antioxidant enzymes, thyroid hormone metabolism and immunity.
• Sources: fish, meat, eggs, wholegrains and Brazil nuts (one or two a day is usually plenty; they are very rich and excess can be harmful).
Copper, manganese and others
• Copper (RNI about 1.2 mg men, 1.0 mg women): works with iron in making red blood cells and collagen, and in antioxidant enzymes. Found in shellfish, nuts, seeds, offal and wholegrains.
• Manganese, chromium, molybdenum and fluoride: needed in tiny amounts for bone formation, enzymes and tooth enamel. Deficiency is very rare in a varied diet.
Upper limits: more is not better
The UK Expert Group on Vitamins and Minerals has set guidance levels for long-term supplement intake, for example about 1,500 mg calcium, 400 mg magnesium (from supplements), 25 mg zinc and 17 mg iron a day. These are for supplements on top of food. If you take multiple products (a multivitamin, protein powder, sports drink and an extra supplement), the amounts add up.
7. Competitive athletes: how nutrition volumes change
Competitive athletes eat more in total, shift carbohydrate up and down with training load, hold protein high and steady, and plan nutrition around the season. The ranges below follow ISSN, ACSM and IOC position stands and are starting points; your coach will individualise them.
Why athletes’ needs differ
Three things drive the numbers: training volume and intensity (more work, more fuel), the demands of the sport (strength, team, endurance or weight-class), and the point in the season (building, competing, tapering or recovering). Protein stays fairly constant because it protects and rebuilds muscle. Carbohydrate changes the most, because it is the fuel that varies with the work. Fat usually fills the remaining energy.
Energy availability: the foundation
Energy availability (EA) is the energy left for the body’s normal functions after training: (energy eaten minus exercise energy expenditure) divided by fat-free mass. Roughly 45 kcal per kg of fat-free mass a day supports health and performance. Persistently below about 30 kcal per kg is called low energy availability and can lead to RED-S (Relative Energy Deficiency in Sport), which affects hormones, bone, immunity, mood, recovery and performance. No macro split fixes under-eating, so eat enough first, then fine-tune.
Targets by type of athlete
Athlete type Protein (g/kg/day) Carbohydrate (g/kg/day) Fat Notes
Strength and power (lifting, throwing, sprinting) 1.6 to 2.2 4 to 7 20 to 35% of energy Protein spread over 4 to 5 meals; carbs fuel heavy sessions
Team and field sport (football, rugby, hockey) 1.4 to 2.0 5 to 8, up to 10 around matches 20 to 35% of energy High-intensity, stop-start work depends on glycogen
Endurance (running, cycling, rowing, swimming) 1.2 to 1.8 6 to 10, up to 12 for very high loads 20 to 30% of energy Fuel during sessions over 60 to 90 minutes
Weight-class or physique (during a cut) 2.0 to 2.4 Lower, set around key sessions Keep to the lower end of 20 to 35% Higher protein protects muscle; see below
Changing volumes through the season
Phase Carbohydrate (g/kg/day) Protein (g/kg/day) Focus
Off-season 3 to 5 1.6 to 2.0 Build muscle, fix weak points, recover; energy matched to lower training
Pre-season build 5 to 8 1.6 to 2.2 Highest training load; fuel it and protect muscle
In-season 3 to 5 on light days, 6 to 10 on match and heavy days 1.6 to 2.0 Perform and recover; avoid calorie deficits
Taper and competition week 6 to 10, rising as training volume falls 1.4 to 1.8 Fresh legs, full glycogen, familiar foods
Changing volumes day to day
Athletes usually adjust carbohydrate to the day’s work and keep protein and fat roughly constant. This illustrative example is for an 80 kg team-sport athlete.
Day type Carbohydrate Protein Fat Approximate energy
Rest or light day 4 g/kg (320 g) 2.0 g/kg (160 g) 1.0 g/kg (80 g) 2,640 kcal
Heavy training day 7 g/kg (560 g) 2.0 g/kg (160 g) 1.0 g/kg (80 g) 3,600 kcal
Match day 8 g/kg (640 g) 2.0 g/kg (160 g) 1.0 g/kg (80 g) 3,920 kcal
Competition-day fuelling
• The days before: for continuous events lasting over 90 minutes, 8 to 12 g/kg of carbohydrate a day for 36 to 48 hours tops up glycogen. For team sports, around 6 to 10 g/kg the day before is typical.
• Pre-event meal (1 to 4 hours before): about 1 to 4 g/kg of carbohydrate, lower in fat and fibre, with a moderate amount of protein. Foods you have practised before work best.
• During: water for under 60 minutes; 30 to 60 g of carbohydrate per hour for 1 to 2.5 hours; up to 90 g per hour for longer efforts, using a glucose and fructose mix.
• Afterwards: if you compete again within 8 hours, aim for 1.0 to 1.2 g/kg of carbohydrate per hour for the first 4 hours, plus about 0.3 g/kg of protein soon after. If you have a full day, normal meals are enough.
• Fluids and salt: weigh yourself before and after training. Replace around 125 to 150% of the fluid lost over the following hours, with sodium in food or drink if sweat losses are high.
Gaining muscle or cutting weight
• Gaining: a small surplus of about 200 to 300 kcal a day is usually enough. A sensible rate is roughly 0.25 to 0.5% of body weight a week for newer or intermediate lifters, and slower for advanced athletes. Faster gains add mostly fat.
• Cutting: aim for about 0.5 to 1% of body weight a week, with protein at the top of the range. Lean athletes should cut more slowly. Avoid cutting during heavy competition blocks, and never use fluid restriction or crash dieting.
• Making weight in combat or weight-class sports should be supervised by a qualified coach or sports dietitian, because large rapid losses harm performance and health.
Evidence-based supplements
Food comes first. A few supplements have good evidence for athletes: creatine monohydrate (3 to 5 g a day for strength and power), caffeine (3 to 6 mg per kg about 60 minutes before, tested in training first), and protein powder or carbohydrate drinks for convenience. Athletes subject to drug testing should use batch-tested products (for example Informed Sport) because contamination occurs.
Warning signs of under-fuelling
Persistent fatigue, frequent illness or injury, stress fractures, poor sleep, low mood, falling performance, and in women missed or absent periods can signal low energy availability. If you notice these, speak to your coach, GP or a sports dietitian before changing your diet further.
Young athletes
These targets are for adults. Athletes under 18 are still growing and should not diet to lose weight or follow adult numbers. Their priority is enough food to support growth, school, sleep and sport, with plenty of carbohydrate, protein at meals, dairy or fortified alternatives for calcium, and regular meals. Agree any plan with their coach and parents or carers.
A simple plate approach
For most meals, build your plate from these parts:
1. A palm-sized portion of protein (about 20 to 40 g).
2. One or two cupped handfuls of carbohydrate, more on heavy training days and less on rest days, choosing wholegrain or high-fibre options most of the time.
3. Plenty of vegetables or salad (half the plate is a good guide), providing fibre and minerals.
4. A thumb-sized portion of fat (oil, nuts, avocado, cheese), choosing mostly unsaturated sources.
5. Fluids to match your thirst and training, mostly water.
Key points to remember
• No single food or nutrient is “good” or “bad”; it is the overall pattern, quantity and consistency that count.
• Protein is the priority for building and keeping muscle; carbohydrate is the priority for fuelling hard training; fat protects hormones and health; fibre and minerals keep the body running.
• Whole, minimally processed foods deliver the best mix of nutrients.
• Supplements fill gaps; they do not replace a good diet.
• Your needs change with your goal, training load, age and health. Ask your coach for personal targets.
This guide is for general education and is not medical advice. If you have a health condition, a history of disordered eating, are pregnant or breastfeeding, or are on medication, seek advice from your GP or a registered dietitian before changing your diet.