There have been a number of childhood obesity intervention studies (Epstein et al., 1998). Almost exclusively the main outcome measure has been weight change: either weight loss or reduction in weight for height. The great majority of studies have involved only a small number of children and have been of relatively short duration. Furthermore most studies have been performed in specialized child obesity centres, mainly in North America, and the appropriateness of generalizing the results to other clinical contexts remains unclear. Although a large number of studies have been performed only randomized controlled studies will be considered in this section.
Few randomized controlled studies have been performed and these have recently been reviewed for the Cochrane Collaboration (Summerbell et al., 2004). Only one study examined the effect of dietary counselling and found no significant difference between a group of 50 prepubertal children who were given dietary counselling and a group who were 'untreated' controls (Flodmark et al., 1993). Other studies focused on physical activity as a means of weight change. In these studies a variety of methods were employed. In one of a number of studies by Epstein, prepubertal children were assigned to either diet alone or diet plus exercise which was provided in the form of an 8-week intensive programme followed by 10 monthly maintenance sessions (Epstein et al., 1985a). Per cent overweight, described as per cent weight for height, was reduced in both intervention groups but was only significantly different at 6 months but not at 12 months following initiation of the intervention.
Epstein has also examined the benefit of a reduction in sedentary behaviour versus an increase in physical activity (Epstein et al., 1985b). The rationale for this approach, often called 'lifestyle activity', is that increasing energy expenditure through normal daily living is potentially a more sustainable form of physical activity than participating in more structured exercise programmes. Statistically significant differences in per cent overweight were found in children in both groups at both 6 and 12 months of treatment. However at 24 months the lifestyle group had maintained their relative weight changes whereas children in the physical activity group had returned to baseline levels (Epstein et al., 1985b).
Behavioural interventions have also been examined. A variety of techniques have been employed and have been shown to be effective compared to conventional treatment, usually dietary advice and medical follow up. Cognitive behavioural therapy, relaxation therapy and family therapy all appear to be effective (Warschburger et al., 2001; Duffy and Spence, 1993; Epstein et al., 1985c; Senediak and Spence, 1985). There is also the suggestion that therapies involving the parents as the main motivators of change are more effective than treatments which are predominantly child focused. However, it is important to note that the great majority of these studies have involved younger children and it is uncertain whether these results could be extrapolated to emotionally challenging adolescents with weight problems.
It would appear from these studies that weight loss is both difficult to achieve and to sustain. It is therefore important to know if weight loss, or even a physical activity intervention per se, may have health benefits in children as in adults. A weight reduction of 10 per cent from baseline in adults has been shown to have significant benefits on cardiovascular morbidity (Krebs et al., 2002). Recent studies have also shown a dramatic impact of weight loss on the risk of diabetes. The Finnish Diabetes Prevention Study and the American Diabetes Prevention Program have both shown that intensive lifestyle intervention in obese patients with impaired glucose tolerance (IGT) led to a reduction in the risk of progression to type 2 diabetes of 58 per cent (Tuomilehto et al., 2001; Diabetes Prevention Program, 2002). This was achieved with an average reduction in weight of only 4 kg over the 3-4 year period of the studies. Unfortunately, none of the randomized controlled studies quoted above appear to have examined the health benefits of weight loss in childhood. Smaller studies have suggested that weight management in children does provide some health benefits especially with respect to CVD risk factors. One small study in children has demonstrated a potentially significant benefit of exercise irrespective of weight loss (Ferguson et al., 1999). Four months of exercise training led to a reduction in fasting insulin concentrations suggesting that activity may have beneficial effects on insulin sensitivity in children as in adults. However, these benefits of exercise training were lost when children became less active again, underlining the importance that any intervention needs to be sustainable. Other studies have shown a significant improvement in blood pressure and lipid profiles (Becque et al., 1988; Rocchini et al., 1988; Epstein et al., 1989; Knip and Nuutinen, 1993) with obesity interventions which were more pronounced if exercise was included as part of the weight management strategy (Becque et al., 1988; Rocchini et al., 1988).
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