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Cereal bars, milk shakes and long-term weight loss in the obese

 

It has become clear that long-term weight loss is difficult to achieve. This meta-analysis examines weight loss in individuals five years after having participated in a structured weight-loss programme, which used either a very low energy diet or a hypoenergetic balanced diet. In very low energy diets (less than 800 calories a day), daily food intake is replaced with nutritionally complete formulas such as energy bars and milk shakes. Hypoenergetic balanced diets (1,200 to 1,500 calories a day) include foods which are normally eaten.

Bottom line

While this paper suggests that very low energy diets offer a promising approach to weight loss in the obese, further research is needed to confirm these findings and extend them to incorporate other aspects of treating obesity.

Reference

JW Anderson et al. Long-term weight-loss maintenance: a meta-analysis of US studies. American Journal of Clinical Nutrition 2001 74: 579-584.

Search

The literature was searched using MEDLINE from 1970 to 1999. References from identified papers and literature reviews were also examined. To be included, studies had to have (i) been conducted in the US (because of differences in weight-management practices in different countries); (ii) included participants in a structured weight-loss programme (as opposed to a self-help activity); and (iii) provided follow-up data for more than two years.

Twenty-nine studies met these criteria. Thirteen studies used very low energy diets, 14 used hypoenergetic balanced diets and one used both. The length of treatment ranged from 8 to 30 weeks (median of 22 weeks for the very low energy diets and 12 weeks for the hypoenergetic balanced diets). The majority of studies included both men and women with participant numbers ranging from six to 508. Ages ranged from 31 to 59 years. Average initial body weights ranged from 74 to 121 kg for women and from 100 to 148 kg for men. Between 50% and 100% of participants completed the follow-up.

The outcome measures were: (i) weight-loss maintenance (in kg); (ii) percentage weight-loss maintenance (weight-loss maintenance as a percentage of initial weight loss); and (iii) reduced weight (weight loss as a percentage of initial body weight).

Results

Four to five years after having participated in a weight-loss programme, on average, participants maintained a weight loss of 3 kg, or 23% of their initial weight loss, representing a reduced weight of 3.2% of their initial body weight. (Thirteen studies with 1,081 participants contributed to these analyses.)

Participants who completed a very low energy diet programme lost significantly more weight and maintained greater weight losses after four to five years than those who completed a hypoenergetic balanced diet programme (see Table 1).

Table 1. Weight maintenance of participants in different groups.

Group

No. of studies

No. of participants

Weight-loss maintenance

% weight-loss maintenance

Reduced weight

 

kg

%

%

Very low energy diets

4

578

7.05

29.4

6.59

Hypoenergetic balanced diets

8

448

1.99

17.8

2.11

Lower exercise

6

272

7.47

27.2

6.66

Higher exercise

6

220

14.99

53.8

12.49

The four studies which implemented the very low energy diets reported weight losses of more than 20 kg; the five studies which implemented the hypoenergetic balanced diets reported weight losses of less than 10 kg.

Six studies examined the effects of exercise on weight-loss maintenance. Initial body weights and weight losses did not differ between those who exercised the most and those who exercised the least. After an average of 2.7 years, those with higher levels of physical activity were more successful in maintaining their weight loss than those with lower levels (see Table 1).

Comment

This meta-analysis has several shortcomings which limit the efficacy of its results. These include the following:

There may be advantages in following a very low energy diet, for example, meal replacements may make it easier for individuals to follow a restricted diet (for those who can follow such a rigorous intervention). However, the evidence from this paper alone is not convincing enough to recommend them. Although it suggests that meal replacements offer a promising approach to weight loss, the treatment of obesity has to include strategies to enable individuals to make healthy changes which can be sustained for life. Treating obesity is much more complex than just reducing calories.