I fear I've not added particularly much in the previous response, so perhaps an analogy;
Think of our metabolism as a bathtub, with a tap filling it with water and an open drain letting the water out. The water is energy (calories).
Water coming in from the tap is our calories consumed. Water leaving the tub via the drain is calories expended. If the drain can remove water (burn calories) as fast as the tap is adding it (consuming calories), then all is good, water/energy balance is maintained.
However, if the tap shoots up in pressure and pumps in three times as much water in a short period of time, the drain will not be able to deal with this and the tub will begin to fill, and overflow. This is the equivalent of eating higher-GI foods; flooding the tub.
The water (calories) will flow over the brim and into the bathroom (adipose tissue). We've now got a mess on our hands. This doesn't change, even if we turn off the tap (consume no more calories) to maintain daily energy balance.
Sure, we can mop up the water and wring it down the drain, but it's going to take us a lot longer than if we had flattened the curve of glycogen consumption and we're not going to get all of it.
The only way to prevent the bathtub from overflowing would have been to simultaneously increase the rate of drainage - i.e. increase physical activity. But this isn't what the standard lifestyle looks like - so many people are consuming starchy carbs as a matter of course, rather than only at physiologically appropriate times, when exercising or expending a lot of calories.
It's tempting to think of energy balance in a neatly partitioned 24hr window, but it's really happening at every moment. Higher spikes in glycogen intake provide countless overflow moments, each of which comes with energy storage as body fat. Relying on equal energy deficit moments at other times of day to balance our energy balance does not provide an equal and opposite energy use, because our metabolism shifts down.
We're simply evolutionarily designed to preferentially store energy.