Instead of the energy taken to grow those plants going to feed people - they are used to grow animals. This takes an enormous amount of input energy from farming the plants, to transporting them to the animals. Not forgetting water transport also. Then there is the energy that is taken to manage the huge sums of waste that these animals produce (most of which is stored in huge silos or pits, which ends up leaching into ground water - but that's another thing). Then there is the energy to transport, kill, transport, package, transport and eventually sell - so the energy / calorie of animal food is no where near efficient as it is for plants and beans. Basically, it is not a closed system - we input so much energy into sustaining our meat habit (as well as the ethical implications of killing 100,000,000-500,000,000 sentient animals a day - including fish and the resulting bycatch)
I think we agree when it comes to the impact of a solution - there needs to be a HUGE concerted effort to even make a dent - people can't immediately change the nature of the worlds largest companies - but I believe that our only hope is to promote local change (to get people to commit to a lifestyle change that has to happen one way or another) - and push for governmental reform - will it be perfect? no. Will it be easy? nope. But we have to start somewhere - and I think diet and local economies might be a good first step.