1. Go for a walk at lunchtime The exercise and fresh air will boost your energy levels, and even if it's just 15 or 20 minutes it will help.
2. Cut back on carbohydrates at lunchtime
Pasta, baked potato, sandwiches ... fast release carbohydrate cause blood sugar levels to rise and fall quickly. A balance of less carbohydrates and more protein and veg should help balance your blood sugar levels. And if you switch to complex carbohydrates like brown rice, lentils and beans, even better.
3. Drink lots of water
Tea and coffee contain caffine and give you a boost, but then you get the drop in energy. They also dehydrate you, so increase your water intake to boost energy and brain power.
4. Go nuts at 3pm
Try snacking on a couple of brazil or almond nuts mid afternoon to keep your energy levels up.