Barnard Neal D, Levin Susan M, Yokoyama Yoko
J Acad Nutr Diet. 2015 Jun;115(6):954-69. doi: 10.1016/j.jand.2014.11.016. Epub 2015 Jan 22.
In observational studies, vegetarians generally have lower body weights compared with omnivores. However, weight changes that occur when vegetarian diets are prescribed have not been well quantified. We estimated the effect on body weight when vegetarian diets are prescribed. We searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials for articles through December 31, 2013. Additional articles were identified from reference lists. We included intervention trials in which participants were adults, interventions included vegetarian diets of ≥4 weeks' duration without energy intake limitations, and effects on body weight were reported. Two investigators independently extracted data using predetermined fields. Estimates of body weight change, comparing intervention groups to untreated control groups, were derived using a random effects model to estimate the weighted mean difference. To quantify effects on body weight of baseline weight, sex, age, study duration, study goals, type of diet, and study authorship, additional analyses examined within-group changes for all studies reporting variance data. We identified 15 trials (17 intervention groups), of which 4 included untreated controls. Prescription of vegetarian diets was associated with a mean weight change of -3.4 kg (95% CI -4.4 to -2.4; P<0.001) in an intention-to-treat analysis and -4.6 kg (95% CI -5.4 to -3.8; P<0.001) in a completer analysis (omitting missing post-intervention values). Greater weight loss was reported in studies with higher baseline weights, smaller proportions of female participants, older participants, or longer durations, and in studies in which weight loss was a goal. Using baseline data for missing values, I(2) equaled 52.3 (P=0.10), indicating moderate heterogeneity. When missing data were omitted, I(2) equaled 0 (P=0.65), indicating low heterogeneity. Studies are relatively few, with variable quality. The prescription of vegetarian diets reduces mean body weight, suggesting potential value for prevention and management of weight-related conditions.
在观察性研究中，素食者的体重通常比杂食者低。然而，采用素食饮食时发生的体重变化尚未得到很好的量化。我们估计了采用素食饮食对体重的影响。我们检索了截至2013年12月31日的PubMed、EMBASE和Cochrane对照试验中央注册库中的文章。从参考文献列表中识别出其他文章。我们纳入了干预试验，其中参与者为成年人，干预措施包括持续时间≥4周且无能量摄入限制的素食饮食，并报告了对体重的影响。两名研究人员使用预定字段独立提取数据。通过随机效应模型得出体重变化估计值，将干预组与未治疗的对照组进行比较，以估计加权平均差异。为了量化基线体重、性别、年龄、研究持续时间、研究目标、饮食类型和研究作者对体重的影响，其他分析检查了所有报告方差数据的研究中的组内变化。我们识别出15项试验（17个干预组），其中4项包括未治疗的对照组。在意向性分析中，采用素食饮食与平均体重变化-3.4 kg（95%CI -4.4至-2.4；P<0.001）相关，在完整分析中（省略干预后缺失值）与-4.6 kg（95%CI -5.4至-3.8；P<0.001）相关。在基线体重较高、女性参与者比例较小、参与者年龄较大或持续时间较长的研究中，以及在以体重减轻为目标的研究中，报告的体重减轻幅度更大。使用缺失值的基线数据时，I(2)等于52.3（P=0.10），表明存在中度异质性。当省略缺失数据时，I(2)等于0（P=0.65），表明异质性较低。研究相对较少，质量参差不齐。采用素食饮食可降低平均体重，提示对预防和管理与体重相关的疾病具有潜在价值。
