Flexible dieting is a structure of dieting based on giving your body what it needs to function and change, whether your goal is to lose fat or gain lean muscle and improve performance. Without restricting any specific food groups or demonizing certain foods.

Protein is one of three main classes of food. Proteins are made of amino acids, which function as a cell's "building blocks." Cells need protein to grow and to mend themselves. Protein is found in many foods, like meat, fish, poultry, eggs, legumes, and dairy products.

Carbohydrates are a combination of starch, sugars and fibre that when broken down provide energy for the body. They are primarily used as a fuel source and they provide us with the energy our brains and bodies need to function.

There are two types of carbohydrates, simple and complex. Complex carbs provide more sustained energy and are found in foods such as wholegrain pastas and breads, while simple carbs are found in foods such as sweets, cakes and biscuits.

Fats are substances that help the body use some vitamins and keep the skin healthy; they are also the main way the body stores energy. In food, there are many types of fats -- saturated, unsaturated, polyunsaturated, monounsaturated, and trans fats. Found in foods such as oils, nuts, fatty fish, nut butters etc.

When we consider the nutritional needs of the body in order to survive and function, we can broadly divide or define the diet into macronutrients (carbohydrate, protein and fat), and micronutrients (vitamins and minerals).

The three macronutrients all have their own specific roles and functions in the body, and all supply us with calories or energy. For this reason, the body requires these nutrients in relatively large amounts to grow, develop and continually thrive. Remember, macro means large!

Micronutrients on the other hand, whilst equally crucial, are required in much smaller quantities (micro = small) to ensure normal metabolism, growth and physical and mental wellbeing. Of course we also need water to survive, which serves as a carrier, distributing nutrients to the body’s cells, and removing toxins and waste products for elimination.

High and low days are a way of alternating your calories on different days of the week, while still keeping your average weekly calories the same. You may have a heavy training day that you'd like more food for, or maybe just to give yourself some more calories for the weekends. You can utilise high and low days and still continue to hit your average weekly calorie target.