The effect of a very low calorie diet on subjective depressive symptoms and anxiety: meta-analysis and systematic review

There are conflicting findings regarding the effect very low calorie diets (VLCDs) have on self-reported depressive symptoms and anxiety levels. Some studies have reported decreased subjective depressive symptoms and anxiety post-diet, whereas other studies have not. Further complicating matters, the protocol for VLCDs vary substantially across studies, which could account for the mixed findings. The primary goal of this meta-analysis and systematic review was to determine the effect VLCDs have on subjective depressive symptoms and anxiety pre- to post-diet. In addition, potential moderators (the presence/absence of behavioral therapy, duration of diet, inclusion/exclusion of low intensity exercise, and amount of weight lost) were examined to assess the effect of procedural deviations across VLCD studies on depressive symptoms and anxiety. A random-effects model was used for the meta-analysis and included nine studies with 16 independent samples. To further explain the results, study rigor was examined in the systematic review, which included 11 studies with 20 independent samples. Depressive symptoms significantly decreased pre- to post-diet when behavioral therapy was implemented during the diet, the duration of the diet was relatively long (8-16 weeks), low intensity exercise was included, and the dieters lost 14.1 kg or more post-diet. However, no difference in depressive symptoms were observed pre- to post-diet when behavioral therapy was not included, the diet was shorter (1-7 weeks), no exercise was implemented and dieters lost <14 kg of weight post-diet. There was no change in anxiety pre- to post-diet. Health care providers involved in supervising VLCDs should consider using a VLCD of at least 8 weeks that includes behavioral therapy and low intensity exercise in order to enhance the potential benefits of VLCDs on depressive symptoms. More research is required to examine the effect of VLCDs on anxiety.