Let's talk about fat. Fat has received a lot of bad press over the past 20 years, but the tide is starting to turn. We need fats to a degree, after all. They help our bodies to function, lubricate our joints, regulate our hormones and make up a good percentage of our brain. Picking quality fats is vital, though – rather than hitting the fast food, go for avocados, olive oil, nuts, butter and oily fish. Stick to the ‘rule of thumb’: a portion of fat should be the size of your thumb.