OBJECTIVE: To assess the effectiveness of dietary interventions and exercise in long-term weight loss in overweight and obese people.
DESIGN: A systematic review with meta-analysis.
SUBJECTS: Overweight and obese adults-18 years old or older with body mass index (calculated as weight divided by the square of height in meters)>25.
DATA SOURCE: Medline, Cochrane Library and Lilacs databases up to March 2003. Also, published reviews and all relevant studies and their reference lists were reviewed in search for other pertinent publications. No language restrictions were imposed.
STUDY SELECTION: Randomised clinical trials comparing diet and exercise interventions vs diet alone. All trials included a follow-up of 1 y after intervention.
DATA EXTRACTION: Two reviewers independently abstracted data and evaluated the studies' quality with criteria adapted from the Jadad Scale and the Delphi list.
DATA SYNTHESIS: The estimate of the intervention's effect size was based on the differences between the comparison groups, and then the overall effect was calculated. A chi-squared test was used to assess statistical heterogeneity.
RESULTS: A total of 33 trials evaluating diet, exercise or diet and exercise were found. Only 6 studies directly comparing diet and exercise vs diet alone were included (3 additional studies reporting repeated observations were excluded). The active intervention period ranged between 10 and 52 weeks across studies. Diet associated with exercise produced a 20% greater initial weight loss. (13 kg vs 9.9 kg; z=1.86-p=0.063, 95%CI). The combined intervention also resulted in a 20% greater sustained weight loss after 1 y (6.7 kg vs 4.5 kg; z=1.89-p=0.058, 95%CI) than diet alone. In both groups, almost half of the initial weight loss was regained after 1 y.
CONCLUSION: Diet associated with exercise results in significant and clinically meaningful initial weight loss. This is partially sustained after 1 y.
It is not surprising that the meta-analysis showed that exercise is not only important to facilitate weight loss, but also to sustain weight loss. I think most have been aware of this for some time.
My main concern with this article is its claim that it is assessing studies with long-term follow-up, which they define as >1 year. However, if we consider obesity a chronic disorder in which a life-long treatment approach is required, 1 year is really of little clinical significance. Another concern is that it does not address effects of dietary interventions on `hard clinical outcomes`. Even if studies did not assess this, its important to convey in the context of a MA.