2.2 Diet and nutrition

The principle of weight gain is simple: energy intake exceeds energy expenditure. The standard daily calorie intake requirement is around 2,000 calories for women and 2,500 for men. If someone reduces daily calories by 500, they may lose about 0.5 to 1lb (0.25-0.5kg) a week depending on factors including age, body composition and activity level.

The NHS considers weight loss of between 0.5lb (0.25kg) and 2lb (1kg) a week to be safe and sustainable, and smaller amounts will gradually add up over time. When losing weight, fewer calories are needed as the person’s body mass becomes smaller. Weight loss often reaches a plateau that can be disappointing for the person concerned and leads to relapse to old habits if it is unexpected. There is ample evidence now that short-term ‘diets’ are almost always followed by weight regain and ‘weight cycling’. 

Gradual changes to diet that are tailored to the individual person are much more likely to be sustainable. The Eatwell Guide (below) is used in the NHS as a visual aid to understand different types of food, goals for relative amounts of each, and brief advice about what to eat less of. It includes population-level suggested calorie intakes for healthy eating for the average man and woman.