Table 3.

Summary of Dietary Interventions Used in Included Studies and Their Effect on QOL

Type of Dietary Intervention Recommendation	Summary of Intervention Effects on QOL and Supporting Quotations
Caloric restriction alone 1,200–1,500 kcal/d BMI based Varying proportions of macronutrient intake	All study interventions of calorie restriction produced improved QOL. No studies clearly indicated whether QOL improvements were independent of weight loss.
Fat restriction alone ≤ 25% of energy from fat	All intervention arms endorsing a low-fat diet produced improved QOL. Most evidence suggested that QOL improvements were not completely attributable to weight loss.  However, improvements in HRQOL did not appear to be dependent solely on weight loss.9  Our findings suggest QOL improvement are limited to the domains of sexual function and energy and mobility independent of the dietary approach used and independent of changes in weight and A1C.15
Low calorie, low-fat ≤ 25% of energy from fat kcal restriction based on baseline weight (1,200–2,000 kcal)	All but 1 study intervention arm endorsing calorie restriction with emphasis on fat reduction produced improved QOL. Evidence suggested that QOL improvements were mostly, but not completely, attributable to weight loss.  We also found significant associations between weight loss, increased aerobic fitness, and improvements in HRQOL and psychological factors, suggesting that these factors may explain, at least in part, the improved HRQOL observed in the diet and exercise interventions.27  Our findings demonstrate that improvements in HRQOL occurring across different diabetes prevention interventions in the DPP were mediated primarily by weight loss, and no significant improvement in global HRQOL occurred through intervention pathways independent of weight loss.14
Low carbohydrate < 20 g/d	Both study intervention arms endorsing low-carbohydrate diets produced improved QOL. Evidence suggested that at least some aspect of QOL improvement was independent of weight loss.  Our findings suggest QOL improvement are limited to the domains of sexual function and energy and mobility independent of the dietary approach used and independent of changes in weight and A1C.15  Compared with a low-fat diet, a low-carbohydrate diet led to similar improvements in the physical aspects of HRQOL and greater improvements in mental aspects of HRQOL as measured by the SF-36. The greater improvement in the mental aspects of HRQOL appeared to be related more to some aspect of the low-carbohydrate diet than to the greater weight loss that occurred on this diet.24
High protein 40% CHO, 30% protein, 30% fat	Evangelista et al12 reported that improvements in QOL for those consuming a high protein diet were associated with weight loss.  The positive effects of short-term weight loss on QOL in overweight and obese individuals have been documented in the obesity literature and confirmed by data from the current study that showed improvements in overall and physical QOL at the end of the 12-week dietary intervention in which there was moderate weight loss.12
Commercial diet	All interventions endorsing a commercial weight loss program such as Weight Watchers produced improved QOL and largely suggested that QOL improvements were related to weight losses.  The current study’s investigators demonstrated that the beneficial effects of weight loss on physical and functional QOL extend to obese breast cancer survivors; however, whether that was a result of the weight loss or the exercise that was part of the weight loss program is difficult to determine.32  Weight strongly predicted total score and all subscale scores, with the strongest relationships for public distress, physical function, and total score.16
General healthy diet	All study interventions of generally healthy diets produced improved QOL. No studies clearly indicated whether QOL improvements were independent of weight loss.

BMI indicates body mass index; CHO, carbohydrates; HRQOL, Health-Related Quality of Life; QOL, quality of life; SF-36, Short Form–36 Health Survey.