Though the national food guide may tell you otherwise, fruit and starchy vegetables are not for everyone. Sure, they’re light years ahead of grains and beans, but for an obese, insulin resistant, sedentary individual it’s just MORE sugar that they DON’T need.
For a relatively lean person with a good level of carbohydrate tolerance (insulin sensitivity), it’s a bit of a different story – at least when we’re talking about whether or not it’s on the ‘consume’ list.
And when talking about the ‘timing’ of these foods, the rule is the same for both.
We want to avoid ingesting high-glycemic fruits and vegetables at times when they’d have a negative impact on our health and body composition.
Which starts with matching our total intake to our activity level. Because exercise is the only way to burn muscle glycogen (stored glucose), and this ‘good starch’ will be used for refilling it (instead of pushing it into fat cells like it does for sedentary folks)
We also want to make sure it’s reserved for AFTER exercise, as opposed to BEFORE – since pre-workout sugar elevates insulin and forces our bodies to favor glucose and glycogen for fuel, instead of body fat.
And though the goal of exercise shouldn’t be ‘to burn fat,’ we may as well optimize our potential to do so. Especially if we can burn it during a nice leisurely low-intensity activity like walking!
For instance, a 2011 study from the European Journal of Applied Physiology demonstrated this perfectly, by separating active young men into three groups and having them go for a brisk walk:
- low-glycemic meal
- low-glycemic meal with fructose
- high-glycemic meal
The group that ate the low-glycemic meal burned primarily fat, while the other 2 groups burned mainly stored carbohydrates. Not only showing us the negative impact of pre-workout sugar, but showing us how ‘fructose’ alone can sabotage an otherwise effective nutrition strategy.
In fact, recent studies have suggested that eating fruit before exercise may inhibit fat burning more than breads and cereal grains, as it not only prevents the use of fat as a fuel source, but it’s been shown to make our cells more resistant to insulin, and increase the lactate concentration during exercise.
If you’re a visual learner, the following chart from a study in the Journal of Applied Physiology gives us a great picture of what can happen to fat burning if carbohydrates are ingested prior to working out. With the top graph showing insulin levels and the bottom one showing fat burning, after participants performed 2 cycling workouts (with 3hrs in between), and either consumed a pre-workout carbohydrate beverage (HI-HI), or didn’t (HI-LOW):
Clearly showing that the group consuming the carbs burned A LOT less fat, because their insulin was elevated pre-workout. And establishing the simple fact, that…
By keeping your pre-exercise meal low-glycemic, you can expect a 100% improvement in fat burning!
Fortunately, after a workout is different, because these higher-glycemic fruits and vegetables are more likely to be stored as muscle glycogen, and support proper recovery. This phenomenon is referred to as the General Homeostatic Recovery Phase. And it’s defined as:
“the resynthesis of fuel stores, free radical quenching, repair of free radical-mediated damage, and the restoration of intracellular electrolyte concentrations and pH”
But for simplicity, we’ll call it the Post-Workout or Post-Exercise Window. And say that it
“replenishes muscle glycogen and supplies anti-oxidants to prevent cellular damage.”
Point being, you can go ahead and enjoy the indulgence of a sweet piece of pineapple or the instant satisfaction from a juicy orange, provided it’s AFTER an exercise session (and provided your leanness calls for it) – as this is not only favorable for your health and body composition, but it’s a great motivator to exercise.
Stay Lean!
Coach Mike
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