Eating around 4 hours before a race isn’t just a random choice – there’s solid reasoning behind it. And this reasoning is why it’s advised to steer clear of munching within that 4-hour window before your workout.
One thing to consider is how your stomach feels. If you chow down too close to your exercise time, especially on a hearty meal, you might end up with some tummy discomfort. This can get worse if what you eat tends to slow down your digestion, like foods rich in fiber, fats, or protein.
But the big deal is avoiding a roller coaster of blood sugar levels, aka ‘Rebound Hypoglycemia’ or ‘Reactive Hypoglycemia.’ It’s pretty straightforward: a sudden spike in blood sugar leads to a surge of insulin, which might overcorrect things and cause your blood sugar to plummet. This low blood sugar can stick around for a while. And if you start exercising soon after eating, things can get trickier. Imagine eating during your warm-up – you won’t get that usual insulin release from carbs because your muscles during exercise don’t need insulin for glucose. In simpler terms, muscles use glucose differently when you’re active compared to when you’re not.
In a nutshell, too much glucose (without moving around) can set off too much insulin, and that can make your metabolism unstable. This can cause unwanted low blood sugar levels before and at the start of your workout. And during this not-so-stable phase, you might find yourself swinging between energy highs and lows, feeling sluggish, and in response to these ups and downs, you might end up taking in way more food than you need, causing tummy troubles from overdoing it right before you workout.