In an ideal universe, you could eat cartons of high-quality vanilla swirl ice cream every night after dinner without remorse.
In the real world, however, there's a price to pay for such indulgence. Ice cream has a large number of calories. Is there a reason why it has to be so very fattening?
In fact, there is. The amount of sugar needed to produce a specific taste is what puts ice cream over the edge on calories.
Ice cream, unlike, say, chocolate chip cookies, numbs your tongue as you eat it. This is the natural effect of applying something cold to the tongue. The more cold ice cream you eat, the harder it becomes for your tongue to register its taste.
Producers of ice cream are aware of this restriction and counter it by a very rational method: they load enough sugar into their product to continue to produce the sensation of sweetness even after the tongue has started is becoming numbed by the coldness. In other words, the amount of sugar necessary to make chocolate chip cookies taste sweet is much less than the amount needed for the same taste in ice cream.
The strategy is very successful, keeping well-made ice cream yummy, even at the bottom of the bowl. However, the price you pay is a double helping of sugar, which means calories, which means fat.