Weight is regulated by the calories we consume from food and drink and the calories we burn  (our metabolic rate (the rate our bodies tick over) + activity we do).

When these two are in balance, our weight remains stable. When we consume more calories than we burn we store them and gain weight. So to lose weight we need to tap into our fat stores by tipping the balance to consume fewer calories than we burn. Small changes can really add up to make a big difference. For example one less 50 calorie plain biscuit per day could help you lose 5lbs (2.3kg) in a year – and one extra biscuit means you could gain that in a year!

The number of calories burned each day is different for different people and largely depends on our weight (heavier people have a higher metabolic rate), how active we are, our age, whether we are male or female, and how much muscle we have. However, on average, women usually need around 2000 calories a day to keep their weight stable and men around 2,500 calories.

The calorie content of 1lb (0.5kg) of body fat is around 3,500 calories. So to lose around 1lb (0.5kg) in a week, we need around a 500 calorie deficit every day (7x500=3,500). This is best achieved by eating fewer calories and being more active each day. 

True weight change is naturally a slow process. If you lose, or gain, weight rapidly, for example in the early days of a crash or low carbohydrate diet, this is mainly due to fluid loss. So don’t be alarmed.