There are four pillars to a successful fitness regime - exercise, rest, nutrition and hydration. Never are these more important than in the run up to race day; forget one of these and your ability will start to crumble.

By now with two days to go (breathe...) you will have done your last tapering run, so the focus now is more on the other three areas.

First: drink enough water today and tomorrow. You want to be nicely hydrated before and during the run - the right balance will help prevent you needing to stop for the toilet during the race.

Second: if you have followed this countdown you will be all prepped and ready to go so you just need to rest tonight and tomorrow - read a good book, indulge yourself in a box set or get lost in Netflix.

Third: eat right. I called on Sarah Flower, author and nutritionist (@mssarahflower), to guide you through what to eat for the next two days:

Nutritionally you need to understand carbohydrates and proteins.

Carbohydrates are what gives our body energy - carbohydrates get converted to glucose, which is stored as glycogen in the muscle and liver. Carbohydrates include, sugar, flours, pasta, bread, rice, vegetables, bananas, cereal - they are the fuel to succeed. Now there are two types of carbohydrates - refined and complex. Put simply, anything that has been altered is refined, so that is white flour, white pasta, white bread and pretty much all junk food carbohydrates, That means that running is not an excuse to gorge on junk food carbohydrates such as donuts or biscuits! Complex carbohydrates include brown pasta, brown flours, brown rice are all wholegrain carbohydrates. Complex carbohydrates take longer for your body to break down, so they release their energy slowly. If you wanted a very quick short burst of energy this is not so vital, but for marathon runners, they want their energy to last so before a run they will eat the complex carbohydrates, low protein and low fat meal to enable them to get through the race. Just like your car runs out of fuel when you put your foot down, your body will start to deplete all its energy reserves after about 60-90 minutes of running. Once this happens, your body will have depleted all its glycogen so you will hit a brick wall. To avoid this, runners need to pace themselves throughout the race as well as continuing to top up with energy gels, bananas or isotonic drinks to maintain the energy reserves.

Proteins on the other hand are made up of amino acids which basically are the building blocks - imagine a brick wall - the wall itself is protein, but the bricks are amino acids. These amino acids, in varying combinations, perform multiple functions throughout our bodies and are vital. For athletes, protein helps repair muscle and damaged tissue. Using this basic information, you can see that eating carbohydrates will power you through the marathon, but protein is needed to help repair after the marathon. Protein sources are meat, eggs, fish, pulses, and milk.

If you are competing in the marathon this weekend, you need to be prepared with the right foods.

Lead Up

You will have been training for weeks so you will already be in a routine of nutritious food, high carbohydrates prior to work outs and high protein for recovery. This will continue the event. You will need to ensure you have enough calories for your body to sustain the training. Experts estimate that you need at least 2500 calories plus an additional 100 per mile you run.

Night before the Marathon

Eat a good nutritious meal. People who run first thing in the morning may want to eat high carbohydrates for their evening meal but I would opt for a balanced meal of complex carbohydrates, vegetables and lean protein - brown pasta dish would be a nice option. I would avoid anything too spicy or too many gas producing carbohydrates - you don’t want to be dealing with an upset stomach, wind or loose bowels when running a marathon!

Day of Marathon

Many people think that eating before exercise is wrong, however it has been shown that this can enhance your performance - after all, would you drive your car at full pelt with very little fuel in the tank? Having said this, stuffing your face too close to the start of the race can result in cramps and nausea, so best get up early to enjoy your breakfast leaving at least 1-2 hours before your run. Your body stores roughly 500g of glycogen in the body (mainly muscle) which will last on average about half a marathon before it is entirely depleted. You therefore need to ensure you are fully stocked with complex carbohydrates. As mentioned above, wholegrains are vital before the race, so eat a high carbohydrate, low protein, low fat meal before you set off. Experts recommend eating about 800 calories. If you don’t want a heavy breakfast you could opt for wholegrain toast, wholemeal bagels and wholegrain cereals. Oats are a great low complex carbohydrate option - they also help settle a stomach so if you are nervous or nauseous this would be a good option. If you can’t eat, then there are energy drinks, cereal bars, bananas, smoothies and gels that may help. You also need to keep hydrated before, during and after the race to avoid dehydration.

During the Marathon

Keep hydrated throughout the marathon. To keep the energy levels up, drink isotonic drinks, energy gels, bananas or energy bars throughout the run. The key here is to choose foods that are easy to digest as well as easy to eat whilst on the run!

Recovery

Your body is going to be aching, sore and depleted. You will need to feed it the nutrients to ensure repair and rejuvenation as well as to replenish your depleted energy/glycogen levels. After a marathon your body produces an enzyme called glycogenase making you highly efficient a replenishing glycogen stores - this needs to be done within half an hour or so of finishing. You can do this by drinking an isotonic drink or energy gel. Smoothies made with banana, oats and lots of berries can help restore depleting energy levels as well as being a great source of vitamins and antioxidants. You can add additional protein by adding some pea protein powder and natural yoghurt. A great recovery shake.

High protein repairs the damaged muscles and tissues - such as lean meat, eggs, pulses, milk, eggs and fish. Phytonutrients and antioxidants such as vitamin C and E are also vital for repair and recovery so try to eat a diet with plenty of fruit and vegetables. Dark chocolate - at least 75% cocoa content, contains flavonols which are shown to help boost heart health as well as repair tissue.