Effective dietary interventions for managing overweight and obesity in children: this month sees the first publications in Kai Tiaki Nursing New Zealand of a best practice information sheet, provided by the Joanna Briggs Institute. These will be published when they relate to Kai Tiaki Nursing New Zealand's monthly theme.

Within the last decade, child obesity has increased dramatically on a global scale. Obesity in young people is associated with complications involving many of the body's systems and these have been comprehensively reviewed.

The evidence base for the longer-term consequences of obesity in adolescents is smaller but compelling. Overweight or obese boys have been shown in several studies to have higher mortality rates. Obesity also causes adverse psychosocial problems such as bullying, discrimination and, in older children/adolescents, low self-esteem. It has been shown that overweight or obese girls of 18 years of age have lower educational and employment attainment, lower incomes and are more likely to be unmarried as adults.

Contributing factors include changes in the food supply (particularly the increased availability of affordable, energy dense foods and sweetened beverages that are marketed aggressively), reduction in physical activity and an increase in small screen sedentary options (television, computer and electronic games). Evidence indicates that a combination of dietary intervention, behavioural therapy and exercise will have a significant impact on weight reduction in overweight and obese children.

Results of studies

One study reported significant post-intervention reductions in percent body fat (three to six percent) in obese adolescents, while another study noted that 20 weeks of treatment including diet and behaviour change (with or without exercise) resulted in a loss of approximately three percent body fat.

Of two waiting list control studies, all patients in a programme that used a low fat diet in conjunction with cognitive behavioural therapy and increased physical activity, lost weight relative to height in a ten-month intervention period. In one study that compared weight loss in a group following diet alone, as opposed to diet with physical activity training, both groups achieved a significant reduction in body mass index (BMI) score over the six-week intervention period.

In another study comparing pre-school vs school-aged children for the effectiveness of intervention (treatment over a year), all children lost significantly more weight when their visits for treatment were frequent. One diet-only trial, with an appropriate control group, resulted in a significant reduction, after 13 weeks' intervention, in Rohrer's Index (weight in kilograms divided by the height in meters cubed) and other anthropometric indices, eg waist to hip ratio and energy intake.

In studies with follow-up of at least one year, mean percent ideal body weight fell. In a study using an initial 10-week protein sparing modified fast (PSMF)--a low-carbohydrate, low-fat, low-calorie diet--a fall in percent overweight was shown at 14.5 months follow-up. In another study after a two-year follow-up, children achieving a ten percent relative weight reduction were classed as "successful weight losers", and, when followed-up at the end of five years, this same group demonstrated sustained weight loss.

Randomised controlled trials

Randomised controlled trials (RCTs) reported results immediately post-intervention or at one or more follow-up times. The "traffic light" (or stoplight) diet is a hypo-caloric strategy that was common to many of the RCTs. This diet is calorie controlled, normally in the range of 1200-1500 kcal/day, with recommended frequencies for consuming food categorised as:

* green: very low in kilocalories and able to be eaten freely, eg fruit and vegetables;

* yellow: core foods making up the bulk of food intake to provide a balanced diet, ie dairy, carbohydrates and proteins; and

* red: high energy density, eg chocolates, crisps and take-aways.

Typically, subjects were prescribed a core 900 kcal/day and could freely select the remaining foods to their daily kilocalorie target. This approach recommends the number of daily/weekly serves of each food group is reduced in total kilojoules and requires food intake to be monitored.

Administering and monitoring the "traffic light" diet was shown to be effective and has been used as a family-based intervention, with parents helping to regulate the availability of "green", "yellow" and "red" foods. Families have been able to reduce the absolute total food serves consumed, "red" foods by half and to increase "green" food consumption.

Non-randomised controlled trials

While hypo-caloric diets were common to the non-RCTs, four studies reported significant weight reduction when PSMFs were instituted as the dietary intervention. These require a high level of medical supervision. One study reported that after eight weeks, significant reductions in percent overweight and increased lean body mass occurred for both pre-pubertal children and adolescents (seven-17 age range). Another study using an eight-week PSMF-based intervention resulted in significant falls in BMI, plus a significant reduction in percent ideal body weight (IBW) at one-year follow-up.

Similarly, a ten-week intervention using PSMF for eight-18 year olds demonstrated improved markers of insulin resistance and relative weight loss. Furthermore, another study using a ten-week PSMF diet showed that: firstly, at the six month follow-up, obese seven-17 year olds displayed a significant decrease in percent overweight; secondly, the PSMF resulted in a greater reduction in percent overweight at 14.5 months, and in super obese eight-13 year olds at six-month follow-up.

In addition to conventional dietary approaches, limited evidence from the non-RCT studies suggests that novel approaches such as altering the macronutrient content of the diet (higher protein) or reducing the glycaemic index require further investigation.

Implications for practice

* Interventions that combine a dietary component, physical exercise and/or behavioural therapy are effective in treating childhood obesity in the short-term. (Grade A)

* The "traffic light" diet is effective in reducing total energy intake, especially from the non-core or "red" foods. However, more studies are needed to establish long-term effectiveness. (Grade B)

* A specific dietary intervention rather than general or non-specific advice will achieve greater weight loss. (Grade B)

* Although there are a limited number of long-term studies, these suggest that effectiveness of a dietary intervention appears to decline over time. (Grade A)

* In the absence of consensus of expert opinion, a rational approach is to base interventions on observational and epidemiological data. Targeting an increase in fruit and vegetable consumption, a reduction in energy-dense, nutrient-poor foods and beverages is appropriate. (Grade B)

* Treatment initiated early may avoid the psychological and physical health consequences that may emerge if overweight and obese children progress to become obese adults. (Grade C) (These grades have been based on the Joanna Briggs Institute-developed 2006 Grades of Effectiveness: Grade A: strong support that merits application; Grade B: moderate support that warrants consideration of application; and Grade C: not supported).

WHAT IS SERVE?--SOME EXAMPLES

Cereals, breads, etc: two slices of bread, or one medium bread roll, or one cup cooked rice, pasta, noodles, or one cup porridge, or one cup breakfast cereal flakes or 1/2 cup of muesti.

Vegetables and legumes (choose a variety): wsarchy vegetables: one medium potato/yam, or half a medium sweet potato, or one medium parsnip; dark green leafy vegetables: 1/2 cup of cabbage, spinach, silverbeet, broccoli, cauliflower or brussel sprouts; legumes and other vegetables: one cup of lettuce or salad vegetables, or half a cup of broad beans, lentils, peas, green beans, zucchini, mushrooms, tomatoes, capsicum, cucumber, sweet corn, turnips, swedes, sprouts, celery, eggplant, etc

Fruit: one piece of medium-sized fruit, eg, apple, orange, mango, mandarin, banana, pear, etc, or two pieces of smaller fruit (apricots, kiwi, plum, figs), or about eight strawberries, or about 20 grapes or cherries, or 1/2 cup fruit juice or quarter of a medium melon (eg, rockmelon), or dried fruit (four dried apricots), or one to one-and-a-half tablespoons of sultanas, or one cup diced pieces/canned fruit.

Milk, yoghurt, cheese and alternatives: 250 ml glass or one cup of milk (fresh, long life or reconstituted ), or 1/2 cup evaporated milk, or 40g (two slices) cheese, or 250ml (one cup) custard, or 200g (one small carton) of yoghurt, plain or fruit, or, as an alternative, try one cup of calcium-fortified soy milk, or one cup of almonds, or 1/2 cup pink salmon with bones.

Meat, fish, poultry and alternatives: 65-100gm cooked meat/chicken (eg 1/2 cup mince or two small chops or two slices roast meat), or 80-120g cooked fish fillet, or, as an alternative, try two smart eggs, or 1/3 cup cooked dried beans, lentils, chick peas, split peas or canned beans, or 1/3 cup peanuts/almonds.

Extras: One extra equals one medium piece of plain cake, or one bun, or three to four sweet biscuits, or half a chocolate bar, or two glasses of cordial or one can of soft drink, or 30g potato crisps (chips), one tablespoon (20g) butter, margarine or oil, or 60g (one tablespoon) jam/honey or two scoops of ice-cream; two extras equal one slice of pizza; and three extras equal one meat pie. (Extras are foods which we can occasionally include for variety. They are generally higher in fat and/or sugar, kilojoules, salt, etc.)

STRATEGIES TO REDUCE FAT INTAKE

* Replace whole milk with reduced fat or skimmed varieties

* Replace sweetened beverages with water or reduced fat milk

* Replace high fat cereal-based foods such as crisps (chips) and packaged snacks with lower fat choices or fruit

* Serve potato without fat

* Trim fat off meat

* Increase vegetables and fruit

THE JOANNA BRIGGS INSTITUTE

* This Best Practice information is based on a systematic review of research conducted by the Australian Centre for Evidence Based Nutrition and Dietetics a collaborating centre of the JBI, originally released within: Collins CE, Warren JM, Neve M, McCoy P, Stakes B. Systematic review of interventions in the management of overweight and obese children which include a dietary component. Int J Evid Based Healthc 2007; 5(1): 2-53

This information has been adapted from the Best Practice series and reproduced with the permission of the Joanna Briggs Institute. The full version may be found at: www.joannabriggs.edu.au.

Table 1: Recommended number of serves per day from each food group.

                                          4-7     8-11    12-18
Children and teenagers:                   years   years   years

Cereals breads, rice, pasta, noodles)     3-7     4-9     4-11
Vegetables, legumes                       2-4     3-5     4-9
Fruit                                     1-2     1-2     3-4
Milk, yoghurt, cheese                     2-3     2-3     3-5
Lean meat, fish, poultry, nuts, legumes   0.5-1   1-1.5   1-2
Extra foods (have no more than)           1-2     1-2     1-3