But the sugar absorbed the energy when it was grown

It's net zero. We can't be generating more heat than the sun is supplying, that breaks the conservation of energy. It's like the fallacy in The Matrix that humans could generate energy via body heat. It's always zero sum.

If I grow corn in June, the corn is absorbing the heat from the sun and converting to sugar. The net effect of growing corn reduces the total heat of the Earth.

When someone eats the corn and their body temp is increases the heat is released. Since all across the earth we are pretty much constantly growing and eating this mostly all evens out. And even if it's not perfectly even, due to seasons, you still over the course of the year have net zero heat vs if humans didn't exist at all.

But we're planting plants and raising livestock. As humans expand we're the ones adding more stored energy. The net energy is still the same. Every bit of sugar burned was heat saved earlier in the growing season.

Isn't all the heat human bodies generate derived from the sun? If humans weren't here, the heat that gets stored as energy in sugar, muscle, fat etc would instead just turn to heat immediately. We aren't creating heat from nothing.