As an exercise physiologist I learned that too little importance is placed on the timing of eating meals. The only thing I did learn was that we shouldn't eat after 7 pm because our metabolism slows down and it will store everything as fat. As a medical doctor with a special interest in sports medicine, supplementation, and nutrition, I have discovered the timing and the macronutrient composition (protein, carbs, and fats)
of meals makes difference in our body fat %, performance and overall health. Most of my patients, including athletes, fitness enthusiasts, and weekend warriors don’t believe this timing is important until I explain how it works, how it is backed up by scientific research and until they have tried it and seen amazing results.
To investigate the timing of meals let’s use the following example: If you
eat a high glycemic - high carbohydrate meal, 1 or 2 hours later you feel tired or like taking a siesta/nap. Why are we feeling like this? It is because the blood sugar is high and the body responds to this metabolic situation by high output levels of insulin. the high levels of insulin make our blood sugar drop quickly, making us feel tired. At the same time the high levels of insulin will overcome and turn off glucagon, GH, and lipase enzyme which breaks down fat from the cells.
What will happen if we time these blood sugar increases to our advantage?
When exercising at high intensity (weight training) the muscles use their own glycogen stores first, and after their own glycogen levels have dropped below a certain level or threshold the muscles have to turn to another energy substrate, in this case fats from our own lipid stores along with some protein.
The timing and macronutrient composition (protein, carbs, and fats) of meals makes a
difference in our body fat % performance and overall health
Why not use our blood sugar?
Because the body wants to keep the blood sugar stable. How do we keep
the blood levels stable? By a process called gluconeogenesis where our
body converts fats and proteins into glucose, or by ingesting other carbs by eating. What will happen then if we keep glycogen levels in the muscles below this threshold and insulin levels low? The muscles will be forced to use fat and/or gluconeogenesis as an energy substrate by activating glucagon, and lipase enzymes to keep our energy levels stable.
How do we time our meals to use our fat stores for energy instead of the muscle glycogen, stores? As I mentioned before, the muscles use glycogen when active but when at rest or inactive the muscles/body prefer the fat substrate for fuel. Fats that come from our fat storage. It is a scientific fact that when muscles are being used, they use glycogen storage, but when at rest they use fats. If we go to bed with low muscle glycogen storage and the muscles are inactive, what will the body use as the fuel of choice? Fats, of course. When we are sleeping our insulin levels are los, our GH increases, therefore fat utilization increases. When the next morning comes our bodies will still be utilizing fat as the fuel of choice because glycogen stores are low. Instead of eating a high carb - high glycemic index breakfast that will replenish the muscle glycogen stores, why not eat a low carb - low glycemic index meal? Our muscles will be forced to continue burning fat for fuel to preserve the storage.
By lunch time when we are going to be lifting heavy weights in 2-3 hours, it is the perfect time to replenish those glycogen stores that were depleted. By using low/moderate glycemic index carbs the body will replenish the muscle glycogen storage without the large spike in insulin
while at the same time allowing the body to continue using lipids moderately because insulin and the sugar
levels are not high enough to turn off the lipase enzymes. In addition our muscles
will be using these replenished glycogen stores again in 2-3 hours during the high intensity
workout. This in turn will deplete the stores again starting the cycle over.
The next question is what can I have for dinner?
Depends. Are you a person that difficulties sleeping are you the person that wants to get lean and muscular fast? If you have difficulties sleeping I recommend a meal that is high in tryptophan (increases serotonin levels) and high/medium glycemic index to help you sleep. If you don't want to do it this way, so you can continue to benefit from optimum meal timing, you can use whole milk (low G.I., high tryptophan) for a snack 1-2 hours before bed time. By the time you go to bed your insulin levels will be low and blood sugars will be stable. If you want to lose fat and have no problems sleeping I recommend another very low glycemic carbohydrate (G.I. less than 50) meal, and large amounts of protein and fat.
Should I snack between meals or before working out?
I recommend snacking between meals when you want to increase your muscular weight. This is a time when protein supplements without carbs work, the best. Never, ever snack before work outs if you want to be leaner because it will raise your blood sugar, increasing insulin and possibly cause reactive
hypoglycemia during your work out, maybe not affecting your performance but the high insulin levels will prevent the use of fatty acids for energy and it will prevent the use of your fat storage for fuel. Costil et. al demonstrated that ingestion of 75 grams of sugar 45 minutes prior to exercise results in elevated glucose and insulin levels resulting in impaired mobilization of lipid stores.
Does this mean that we need to follow this 24 hr. cycle?
NO, you don't have to follow the cycle. It depends on your lifestyle, work, etc. You can rotate it, but the cycle presented here is the most effective method to becoming learner and more muscular without the aid of steroids.
Glycemic index - values how promptly and rapidly glucose enters the blood after food ingestion.
The glycemic index is affected by:
combination of foods
duration and manner of cooking
degree of ripeness and cultivation method
Examples of low glycemic:
Almost all the vegetables except corn, white potatoes and carrots
Pasta (even though pasta is low I do NOT recommend it)
Do not use breads or rice for dinner - their high index foods