When is the best time to train? By Brad Schoenfeld There is a growing sentiment that cardio should be performed first thing in the morning on an empty stomach. The theory behind this belief is as follows: A prolonged absence of food brings about a reduction in circulating blood sugar, causing glycogen (stored carbohydrate) levels to fall. With a reduced availability of glycogen, your body tends to rely more on fat—rather than glucose—to fuel your workout. Under ideal conditions, this should result in an increased oxidation of fat during exercise.But biologic processes don’t necessarily take place under ideal conditions. Therefore, although training after an overnight fast might burn a greater percentage of fat calories during exercise, it doesn’t necessarily translate into more fat loss. The human body is a very dynamic organism and continually adjusts its use of fat for fuel. This process is governed by a host of factors (including enzyme levels, substrate availability, internal feedback loops, etc.) that can literally change by the moment. Thus, simply looking at the amount of fat burned during exercise is shortsighted. Fat burning must be considered over the course of an entire day—not on an hour-to-hour basis—to have any meaning.Further, a pre-exercise meal allows you to exercise more intensely (as is required in high-energy interval workouts). In order to perform at a high level, your body needs a ready source of glycogen; deplete your glycogen stores and your performance is bound to suffer. Compounding matters, not everyone functions well first thing in the morning. If you’re more of a night owl, chances are that you’ll sleepwalk through a morning workout. The net result is that fewer calories are burned during activity—and, perhaps just as significantly, during the postexercise period as well. Remember that following a workout, your body continues to oxidize fat at an accelerated rate via EPOC. And remember that higher-intensity training burns a much greater amount of fat postexercise than lower-intensity training. Impair your ability to train intensely (as can be the case when you abstain from eating) and you’ll inevitably impair your ability to burn fat.What’s more, only about half of the fat utilized during aerobic exercise is mobilized from subcutaneous adipose tissue; the balance comes from fat stored intramuscularly (within muscle). The important point here is that intramuscular fat has no bearing on aesthetic appearance; it’s the subcutaneous fat that influences body composition. Consequently, the actual fat-burning effects of the strategy are far less than it would appear on the surface.Finally, studies have shown that eating before exercise actually increases caloric expenditure. This apparently is related to the thermic effect of food (TEF). You see, every time you eat a mixed meal there is a corresponding increase in metabolic rate. When exercise is performed after the consumption of food, metabolism is heightened by about 20 percent over fasting levels. Better yet, these effects are maintained for up to three hours postworkout. And since burning more calories means burning more fat, eating before cardio can have thermogenic effects on exercise.The bottom line is that, from a results standpoint, you shouldn’t go crazy worrying about when to train. Understand that simply increasing the percentage of calories burned from fat doesn’t necessarily translate into an improved body composition. Not that there’s anything wrong with performing cardio after an overnight fast, but be aware that there are potential drawbacks as well as benefits to this approach.The best advice is to exercise when you are at your best and when it’s convenient. If you are a morning person, go ahead and train early. But if you don’t really get going until you’ve been awake for several hours, by all means train later in the day. All things considered, it really won’t make much of a difference in your results.
Posted on: Thu, 22 Aug 2013 19:09:20 +0000
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