Advice on diet and making changes

• Tailor dietary changes to food preferences and allow for a flexible and individual approach to reducing calorie intake.

• Do not use unduly restrictive and nutritionally unbalanced diets, because they are ineffective in the long term and can be harmful.

• Encourage people to improve their diet even if they do not lose weight, because there can be other health benefits.

• The main requirement of a dietary approach to weight loss is that total energy intake should be less than energy expenditure.

• Diets that have a 600 kcal/day deficit (that is, they contain 600 kcal less than the person needs to stay the same weight) or that reduce calories by lowering the fat content (low-fat diets), in combination with expert support and intensive follow-up, are recommended for sustainable weight loss.

• Consider low-calorie diets (800–1600 kcal/day), but be aware these are less likely to be nutritionally complete.

• Do not routinely use very-low-calorie diets (800 kcal/day or less) to manage obesity (defined as BMI over 30).

• Only consider very-low-calorie diets, as part of a multicomponent weight management strategy, for people who are obese and who have a clinically assessed need to rapidly lose weight (for example, people who need joint replacement surgery or who are seeking fertility services). Ensure that:

• the diet is nutritionally complete
• the diet is followed for a maximum of 12 weeks (continuously or intermittently)
• the person following the diet is given ongoing clinical support.

• Before starting someone on a very-low-calorie diet as part of a multi-component weight management strategy:

• Consider counselling and assess for eating disorders or other psychopathology to make sure the diet is appropriate for them.
• Discuss the risks and benefits with them.
• Tell them that this is not a long-term weight management strategy, and that regaining weight may happen and is not because of their own or their clinician's failure.
• Discuss the reintroduction of food following a liquid diet with them.
• Provide a long-term multicomponent strategy to help the person maintain their weight after the use of a very-low-calorie diet (see implementing lifestyle interventions in the obesity pathway).
• Encourage people to eat a balanced diet in the long term, consistent with other healthy eating advice.

Further information on healthy eating can be found at the NHS choices website.

See also lifestyle in this pathway, and the NICE pathway on obesity.