Carbohydrates of some kind will form the bulk of the bodybuilder’s diet, in particular when adding mass or bulking. Even when cutting, the consumption of carbohydrate, especially the type and timing is still crucial to achieving your goals.

Types of carbohydrate

Sugars - the simplest form of carbohydrate and the building blocks of more complex carbs, sugars are single or double units known as saccharides. Monosaccharides, such as glucose, fructose and galactose are single unit sugars, while disaccharides, such as sucrose (two glucose molecules) and lactose (glucose and galactose) are made up of two monosaccharides, joined together.

Oligosaccharides - these molecules are made up of short chains of monosaccharides (about 3-20).  They often pass through the small intestine into the colon, where they are digested by the so-called ‘friendly bacteria’, helping them to survive and multiply in the gut. For this reason, some oligosaccharides, e.g. FOS (fructo-oligosaccharides) are known as prebiotics. As oligosaccharides taste slightly sweet but are not absorbed, they are used as bulking agents in low calorie granulated sweeteners.


Polysaccharides – these large molecules are made up of many hundreds of monosaccharides, joined with different bonds creating unique structures. Glycogen is a storage carbohydrate composed of many glucose molecules and housed in the muscle and liver as an energy store, to be broken down when energy supplies are required. Starch is the plant equivalent of glycogen, acting as an energy store.


Dietary fibre - this is the indigestible part of carbohydrates, consisting of non-starch polysaccharides (NSP) and other molecules such as oligosaccharides, inulin and pectin. These molecules reach the colon relatively unchanged. Soluble forms of fibre may be used by the microflora in the colon for energy, helping to maintain adequate levels of ‘friendly bacteria’. These bacteria, when digesting the soluble fibre, produce by-products such as short chain fatty acids, which are known to have considerable health benefits.  The insoluble fibre acts to absorb water and produce healthy bowel movements by creating large, soft stools that pass through the system more rapidly.

Classifying carbohydrate

There are numerous methods of classifying carbohydrates, depending on their structure or digestibility and absorption. Probably the most relevant for bodybuilders is the glycaemic index or GI, which is broadly similar (although not identical to) classifying carbohydrates as simple and complex.

The GI measures the reaction of the blood glucose levels to consuming a carb-containing food when compared with pure glucose, which has a GI of 100. Low GI foods, below about 55 cause glucose levels in the blood to rise only slowly and over a long time period, compared with high GI foods of over 70, which lead to a rapid but short lived rise in blood glucose.

In practical terms, a low GI food with its more sustained release of glucose into the blood will keep you feeling full for longer compared with a high GI food that will satisfy hunger only for a short time period. The situation is complicated by the fact that consuming different foods with one another will alter the GI. Thus, eating high GI white bread with butter will lower the overall blood glucose response, so lowering the glycaemic load. Fat and protein both act to slow the absorption of glucose from carb-containing foods, reducing the glycaemic load of the meal.

The most biologically relevant method of classifying carbohydrates is by the insulin index or II. This describes the response of blood insulin to consuming any food, not just one that contains carbohydrate. Some meats and other low carbohydrate foods evoke an insulin response without a glycaemic response. The insulin index may therefore be of most use for dietary management.

Primary uses of carbohydrate - energy provision. 

Digestible carbohydrate, in whatever form consumed is ultimately broken down into its constituent monosaccharides and absorbed into the bloodstream via the liver. The monosaccharides may be converted to glucose and used immediately as an energy (ATP) source via glycolysis, the TCA cycle and oxidative phosphorylation. Alternatively, they will be stored (associated with water) as glycogen in both the liver and skeletal muscle. This energy store can be quickly mobilised to supply the muscles and brain (which relies solely on glucose as its energy source).

The capacity for storing carbohydrate is limited when compared to the near limitless amounts of fat that can be stored in the body. Therefore, if excess carbohydrate is consumed beyond the body’s needs, it will be transformed and stored as adipose tissue.

Relevance of carbohydrate in the bodybuilding diet


Carbohydrates play a pivotal role in the bulking diet of any bodybuilder. Not only do they add calories to ensure energy excess and provide valuable vitamins, minerals and fibre, they can also ensure that muscle recovery is swift and effective following training.

The bulking diet should be largely composed of low to moderate GI carbohydrates, to keep blood glucose and hence insulin levels largely stable. Examples are wholemeal and brown bread, brown rice and wholewheat pasta, sweet potato, basmati rice and most fruit and vegetables. The pre-workout meal should contain sufficient amounts of low GI carbs to ensure the training is adequately fuelled.

Post workout carbohydrate form and timing is subject to much debate. One argument is that, by consuming a high GI carbohydrate such as dextrose or maltodextrin with whey, immediately post workout, insulin levels are spiked, thus promoting the storage of protein and carbohydrate and maximising recovery of carbohydrate stores and repair of muscle damage (leading to muscle growth).

However, there are many arguments against the need for this immediate supply of quick acting carbohydrate. These suggest that equal; if not better results can be gained by consuming a meal containing low to moderate GI carbohydrate.

For athletes training for fitness or endurance and not muscle gains, fast acting carbohydrate, immediately post training is of great importance.


The trend when attempting to lose body fat is to minimise intake of carbohydrate. While reduced intakes are advisable for fat loss, elimination is not necessary, merely smaller portions of low GI carbs.

Pre- and post-workout carbs must be consumed in adequate quantities to fuel training and recovery or progress will be hindered. Again, low GI carbohydrate, in the post post workout meal (PPWO) are favourable to fast acting ones.

There are various diets that focus on the timing and type of carbohydrate. Timed ketogenic diets (TKD) will eliminate virtually all carbohydrate except for those consumed around training. This diet induces periods of ketosis, at which point fat stores are mobilised and used for energy, in absence of carbohydrate stores and can therefore contribute to fat loss.

Cycled ketogenic diets (CKD) are similar to TKDs but carbohydrate intake is cycled, always being high around workouts but also including days of higher carbohydrate intake over all, followed by subsequent low carb days and depletion training (high rep ranges) before the next higher carb day.

Ultimately, any cutting diet is arduous and challenging and the choice of diet will depend upon the individual, their goals and their compliance.


  • Carbohydrates have many forms – from monosaccharide sugars to large complex starch and storage polysaccharides
  • The glycaemic or insulin indices classify carbohydrates by their effect on blood glucose or insulin. While other methods of classification exist (simple / complex, starchy / fibrous), The GI and II are the most relevant to dietary management
  • Carbohydrates provide both an immediate source of energy for brain and muscles and can also be stored as glycogen

• Carbohydrates provide the bedrock of bulking diets adding calories, fibre and micronutrients and also ensure that cutting is effective by providing adequate fuel for training and recovery.



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