Carbohydrates [CHO] are the primary fuel needed for all high-intensity forms of exercise, whether aerobic or anaerobic. Muscle glycogen can account for up to about 2000 calories of stored energy depending on the athlete, the liver can store about 200 calories of glycogen, and of course, highly regulated levels of glucose circulate in your blood all of the time. Stored CHO in your muscles (glycogen) will be a primary factor in determining your ability to exercise at a high level for any length of time, and will help determine your ability to perform longer bouts of exercise at most any intensity.
CHO ingestion prior to exercise helps maintain or increase glycogen stores if they are depleted. CHO ingested during exercise can delay the onset of fatigue and increase the ability to perform at higher intensities by increasing the availability of blood glucose. CHO ingested immediately after exercise will stimulate recovery of lost glycogen stores, address potential low blood glucose issues associated with “bonking,” and will stimulate the production of recovery hormones insulin and insulin-like growth factor [IGF]. Insulin and IGF are “anabolic” hormones, meaning they “build up.” Namely, they stimulate the synthesis of new glycogen and new proteins, both essential for recovery, as well as the storage of fat. This CHO can be in any form that is well tolerated and easily digested by the athlete and in an amount that is proportional to the duration and intensity of the training session.
Should I eat large quantities of carbohydrate at every meal, then? They are essential for hard training, right? Probably not, because it would create a hormonal environment after every meal that would cause your body to store CHO and fat. If your CHO stores are already mostly recovered, this would manifest itself largely as fat storage and added weight. More balanced meals with moderate protein, fat and CHO should be the mainstay of an athlete’s diet, with CHO being mostly in the form of vegetables, fruits and unrefined grains.
Consuming extra CHO at meals should be a focus only when in need of recovery from heavy training or racing sessions that leave you thoroughly depleted, but otherwise, a generally healthy, balanced diet with lots of vegetables, fruits, nuts, legumes, lean meats, maybe some dairy, and maybe some unrefined grains should adequately provide CHO, especially if training sessions are done with extra CHO intake during and immediately post-workout. But, more importantly, getting a mix of CHO, protein and fat from a variety of real-food sources like those just listed will also provide a high quality mix of vitamins, minerals, and beneficial phytochemicals that will keep you training stronger and healthier than you would if you were to consume a high proportion of refined foods that have been largely stripped of their nutritional value (e.g. white flour-based foods or refined sugars).
Fruits, vegetables and legumes are all good sources of CHO, but compared to most grain products, they are much better sources of vitamins, minerals and healthy phytochemicals. For that reason, I would definitely consider looking into places in your diet where you could consume fruits or vegetables, rather than grains (especially if they are refined grains). Your body will have better mineral availability for good water balance, neural function, alkaline balance to help prevent protein breakdown, possibly bolster your lactate buffering capabilities, and probably improve bone health, as well as provide a lot of antioxidant support for your immune system that will likely reduce general stress on your body and reduce your risk of minor illnesses that may limit long-term development.
In general, you should consume a lot of CHO and some protein immediately following a moderate to strenuous workout that leaves you depleted. Refined CHO may be good at these times because they are so quickly and easily absorbed, and will help create a greater insulin and IGF response that may bolster recovery. Your body will be the most receptive to the CHO immediately after training, and it is therefore the best time to restore lost glycogen if you need it replenished quickly for your next training session or race. It is also the time your body is the most sensitive to insulin and will produce the most IGF, both of which will help rebuild damaged muscle tissue and generate new enzymes to hopefully come back fitter for the next workout or race.
After a long, hard 4-6 hour workout with some good intensity and dead legs at the end, I would advocate for having about 4-5 times your body weight [in pounds] in calories of CHO. So, if you weigh 150 pounds (about 68kg) and you come back from a 5 hour ride with lots of climbing and hard efforts, I would try to eat about 600-750 calories (~190g) of CHO in the first 60-90 minutes after you finish. Hopefully that recovery effort begins within the first 15-30 minutes of finishing. Along with that, it’s good to consume about 1/3 that many calories of protein (roughly 200-250 in this case). That would be about 1000 calories in the first 90 minutes after an intense, long workout, in this example.
Having a baseline of sound nutrition usually with some extra CHO during exercise and extra CHO and protein immediately following, an athlete should be able to make the most of their training and general health.