肥胖和超重成人采取素食可显著减轻体重

亚特兰大——根据南卡罗来纳州立大学Arnold公共卫生学院健康促进、教育与行为系的Gabrielle Turner-McGrievy 博士在肥胖周上展示的资料，不强调计算热量的素食主义和严格素食主义饮食可使超重和肥胖者8周和6个月体重减轻幅度显著超过接受含肉类饮食的患者。

New DIETs（进行新的饮食干预，促进减重治疗）是第一项直接比较未限制热量的素食主义和严格素食主义饮食以及杂食饮食对体重的影响的随机研究。63例平均年龄为49岁、平均体重指数为35 kg/m2 的成年人（73%为女性，79%为白人）随机分组接受以下5种饮食方式：严格素食主义饮食、素食主义饮食、鱼类素食主义饮食、半素主义者饮食和杂食饮食。所有5种饮食方法都强调摄入低脂、低糖指数食品，但未要求限制热量。所有参与者每周参加1次会议，了解更多关于其分配到的饮食类型的知识。所有饮食方法强调尽可能消耗未经加工的食品。将筛选显示为饮食失调症类似行为阳性的患者排除。

一项意向治疗分析的结果显示，8周时，接受以植物为基础饮食的研究组体重平均减轻了8~10磅(约合3.6~4.5 kg)，而消耗一些肉类食物的受试者平均体重减轻了5磅(约合2.3 kg)。6个月时，严格素食主义饮食组、半素食主义饮食组、鱼类素食主义饮食组和杂食饮食组体重分别减轻了大约7%、4%、3%和3%。

“在未计数热量的情况下，所有研究组体重显著减轻，但严格素食主义者减轻的幅度最大。”严格素食主义组在8周时仍依照饮食方法的受试者约占一半，6个月时降至30%。但研究者发现，严格依照饮食方法并不是完全必要的，因为已将饮食模式降至较低的水平，即使受试者在饮食中增加了一点奶酪或肉类，也不会恢复到研究前的体重。关于以植物为基础饮食组体重减轻幅度更大的确切原因尚不清楚，但各饮食组的主要营养素含量存在显著差异(P＜0.05)，严格素食主义饮食组饱和脂肪的降低幅度更大，素食主义和严格素食主义组的胆固醇水平降低也大于其他组。

研究者总结认为，对于超重和肥胖患者，除限制热量外，逐步减少饮食中肉类含量和过渡至以植物为基础的饮食方式，也是一种有效的减重方法。

肥胖周是由肥胖学会和美国代谢与减肥手术学会主办的。Turner-McGrievy博士披露无相关利益冲突。

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By: WHITNEY MCKNIGHT, Clinical Endocrinology News Digital Network

ATLANTA – Vegetarian and vegan diets that did not emphasize counting calories led to more weight loss over 8 weeks and at 6 months than did diets that included meat, according to data presented at Obesity Week.

"We’re not trying to get people to lose weight just so they can look attractive," said Gabrielle Turner-McGrievy, Ph.D., in an interview. "We’re hoping they will choose a healthy body weight to prevent diabetes and cancer."

The results are from the first randomized study to directly compare the effect of vegan, vegetarian, and omnivorous diets, without caloric restrictions, on body weight, said Dr. Turner-McGrievy, of the department of health promotion, education, and behavior at the Arnold School of Public Health at the University of South Carolina in Columbia.

In the New DIETs (New Dietary Interventions to Enhance the Treatments for Weight Loss) study, 63 adults (73% female, 79% white) with a mean age of 49 years and a mean body mass index of 35 kg/m2 were randomly assigned to one of five diets: vegan, vegetarian, pesco-vegetarian, semi-vegetarian, and omni-vegetarian. All five dietary approaches emphasized low-fat, low-glycemic-index foods but did not require caloric restriction. All participants attended weekly meetings to learn more about the type of diet they had been assigned. All diets stressed consumption of foods that were as unprocessed as possible. Participants who screened positive for eating disorder–like behavior were not included in the study.

An intent-to-treat analysis showed that at 8 weeks, the groups that followed a plant-based diet had lost an average of 8-10 pounds, while those consuming some meat lost an average of 5 pounds.

At 6 months, the vegans had lost about 7% of their body weight, the semi-vegetarian group had lost about 4% of their body weight, the pesco-vegetarian group had lost about 3%, and the omnivorous group had lost about 3%, Dr. Turner-McGrievy reported.

"All groups lost a significant amount of weight without having to count calories, but it was greatest in the vegan group," she said. Compliance in the vegan group at 8 weeks averaged about half; at 6 months, it had dropped to 30%.

"Our message here is that adherence may not be completely necessary," she said. "We shifted people so far down the dietary spectrum that even if they added a little cheese or meat here or there, they still weren’t going back to where they were before."

The exact reason for the greater weight loss in the plant-based diet groups was not clear, said Dr. Turner-McGrievy, but she and her colleagues theorized that changes in macronutrient content, which were found to be significantly different across groups (P < .05), may be a factor. "When we looked at the nutritive changes of these five different diets, we saw a much greater decrease of saturated fat among the vegan diet group," she said. "Vegetarians and vegans also decreased their cholesterol more than the other groups."

When Dr. Turner-McGrievy was asked whether any groups consumed more food, on average, than other groups, she said her team had not determined if there were different levels of hunger between the groups. Study participants were enthusiastic about the "freedom" they had from calorie counting: "On calorie-restricted diets, if at the end of the day you’ve reached your calorie allotment, but you’re still hungry, then you go to bed hungry," she said.

Despite the limited sample size and duration of the NEW DIETs study, Dr. Turner-McGrievy said one of the study’s implications is that when it comes to treating obesity and its attendant comorbidities, there can be a focus on nutrition. "It moves this area of science forward and shows there is another approach that can be used instead of calorie restriction," she said. People with obesity could also be placed on a "stepwise" system, where they start out eating slightly less meat, and eventually move to a more plant-based diet, she noted.

Obesity Week was presented by the Obesity Society and the American Society for Metabolic and Bariatric Surgery.

Dr. Turner-McGrievy did not have any relevant disclosures.