If you are doing moderate amounts of exercise, avoid problem foods including once you have food intolerances to, and eat enough food and get enough fat you may feel more energy. The drop in energy thing mainly affects people who are extremely active pushing the limits of human endurance. That said if you go straight carnivore cold turkey so to speak, most people do have a significant adjustment period for the first 3 weeks or so.

It's worth doing a bit of research first to see what people are reporting and how it might affect you so you can plan and know what to expect.