Diet

Prior to commencing any dietary treatment, the first stage in management should be the development of a regular eating pattern and improving the quality of the diet. Food labelling, meal planning, portion sizes, shopping and healthy eating recommendations are all important aspects which need to be addressed initially.

Energy deficit strategies were reviewed by the Dietitians in Obesity Management (UK) (DOM UK) and include: The 600kcal deficit approach, meal replacements, very low energy diets, low glycaemic index diets and low carbohydrate diets.

The 600kcal deficit approach

This consists of restricting energy intake to 600 kcal below estimated energy expenditure. Research suggests that greater energy restrictions do not lead to greater weight loss in free-living subjects.

Meal replacements

Meal replacements offer pre-packed, portion-controlled products, usually vitamin and mineral fortified, to replace either one or two meals per day, allowing one calorie controlled meal using standard foods (and snack/s). Typically meal replacement programs provide 1200- 1600 kcal per day.

Very low energy diets (VLCD)

Defined as total diet replacements with an energy content < 800 kcal and > 450 kcal/day, usually in the form of liquid drinks but occasionally allow a daily meal based on food. VLCDs should not be used as a first line dietary treatment and should be reserved for use in those with a BMI  > 30 kg/m2  with continuous use limited to a 12 week treatment period. Close medical and dietary supervision are essential.

Low glycaemic index

Glycaemic index (GI) is a physiological way of ranking carbohydrate foods. It is defined as the area under the two hour postprandial glucose concentration curve per 50 g of available carbohydrate. Foods are ranked by low, medium and high GI. It has been suggested that a low-GI diet has beneficial effects on appetite, energy intake, and thus induce an energy deficit.

Glycaemic load (GL) is a more recent concept which accounts for the GI of a food and the carbohydrate in the portion of food.

Low carbohydrate

Defined as limiting carbohydrate to 20-40 g/day, whilst consuming foods rich in protein and fat. Initial weight loss with a high-protein, low-carbohydrate diet is mostly due to losses of glycogen and associated water. The satiating effects of protein also encourage weight loss.

Lifestyle

When considering dietetic treatment, it is important to consider an obese individual's lifestyle, particularly issues which may affect their food choices or meal patterns. Examples of these include work patterns, family commitments, activity levels and income. These issues could be significant factors, not always appreciated by individuals, in deciding which approach might be most effective. Discussing these matters with the obese individual could help them adapt to the dietary intervention more effectively.

[Fiona Sim and Claire Bonner]