The major finding of the present meta‐analysis was the association between improvement in physical disability and weight reduction, which showed that disability reduction could be predicted from weight loss. Previous category 1A evidence support the use of weight reduction in the treatment of obese patients with OA, and operational considerations may be given on how these patients may reduce body weight.61
This study presents evidence‐based estimates from a meta‐analysis to support the use of weight‐loss regimens in the clinical management of OA in clinical rheumatology.
The present meta‐analysis shows that there are few high‐quality RCTs that can be used to provide evidence, and we have found a broad spectrum of heterogeneity in the interventions.12
Diversity across studies was substantial, and the reduction in both pain and self‐reported disability was weak, although statistically significant, whereas no clinical effect could be detected using the Lequesne (global OA) disease index. Inspired by studies on heart disease and stroke,62,63
we aimed to determine the dose–response effect applicable for clinical practice, when recommending weight reduction to patients with knee OA. The meta‐regression models seemed inconsistent when the reduction in pain (ie, ES pain score; fig 3A,B) was used as dependent variable versus weight change. The predictability of effect on pain was questionable to use for clinical practice. By contrast, weight loss predicted (with great certainty R2
75%) the patients' reduction in self‐reported disability (ie, ES disability score; fig 3C,D). Based on our estimates, patients should achieve more than 5.1% weight loss, with a loss of at least 0.24% per week, to experience a significant reduction in disability. This would result in an ES
0.34 and ES
The meta‐regression analysis, which owing to the number of included randomised patients is considered “gold evidence”,11
points towards recommending overweight patients with knee OA to reduce their body weight with at least 7.5%, obtained with an intensity being at least 0.6% per week would result in an at least moderate clinical effect. Finally, if we apply the general dietary (public health) approaches to reduce body weight64
to overweight patients with knee OA, using a rate of weight loss by 0.5 and 1.5 kg/week,61
the present meta‐analysis shows that a 10% weight reduction will result in a moderate‐to‐large clinical effect according to self‐reported disability (ES
0.67), preferably reached within 12 weeks of treatment. A weakness of the present analysis was the few RCTs available for assessment, which emphasises the need for more and larger trials. Although only four studies were applicable in the analysis, based on the Jadad score, at least two of the studies were of top quality in this field.
In general, state‐of‐the‐art weight loss policy among obesity specialists is that the overweight individual initiates a 10% reduction in body weight, which reduces multiple risk factors.4,65
With these guidelines, the effect of the weight loss may be achieved within a few months, resulting in a clinical ES larger than most non‐operative treatments systematically reviewed, applying meta‐analyses,66,67,68,69
and at least comparable to the possible effect of walking.70
In the present meta‐analysis, it is obvious that the strategies applied in the individual RCTs combine great diversity in both magnitude and intensity of the (weight‐reducing) dietary strategies. The “weight loss (3.7%) regimen” used in the quantitatively largest trial58
would probably not be acknowledged as an anti‐obesity approach71,72,73
following 18 months of treatment.
On the basis of the changes in pain scores reported by Messier et al
post hoc calculations from the data show that clinical efficacy can be documented only when weight loss is added to an exercise treatment (ES
0.44). We argue that the reason for this finding is a consequence of more attention, as has been observed in other patient groups with chronic pain.74
When compared with the control group, the dietary intervention failed regarding both weight reduction and pain relief despite a significant within‐group 16% pain reduction following 4.9% weight loss after 18 months of treatment.58
Interestingly, the exercise‐only group—as the “only” of four different intervention groups—did not experience any significant pain reduction (6%) in the study by Messier et al
By contrast, the healthy‐lifestyle (control) group experienced a statistically significant 17% pain reduction58
compared with the 30% pain reduction observed following “diet plus exercise”.58
In conclusion, professionals treating knee OA should bear a possible weight reduction in mind whenever a patient is significantly overweight. The patients ought to be encouraged to reduce their body weight, at least by 5% within a 20‐week period, to experience the symptomatic relief.