You’re getting a lot of flak, but this is sort of the plot of Soilent Green, without the twist. With explosive population growth, it’s not an impossible scenario.

What’s the question, though? Is it possible? Sure, anything is. Why insects, though? There are plenty of other sources of protein, and today vegans (for whom eating even insects is streng verboten) can build healthy diets, even if they have to work a little harder and be more conscious about it. Insects would be yet another level of inefficiency in the system: it’s nearly always most efficient to get nutrients from the most base layer, plants (or fungus, whatever). If all you’re going for is pure efficiency, plants do it all. You may want to kill yourself just to end the culinary misery, but we’re not taking about pleasure or quality of life, only efficiency and base dietary needs.