Low-carb and low-fat diets equally good for weight loss
Both low-fat and low-carb diets work equally well to help people lose weight over two years, new research has shown. In addition, the low-carb diet may also boost levels of 'good' cholesterol, although it's not clear how much difference this would make to your overall health.
What do we know already?
The quest to find a diet that helps people lose weight goes back decades. In recent years, there's been much discussion about the merits of low-fat diets, compared with low-carbohydrate diets.
Research shows the low-carb diet works well for short-term weight loss, but there isn't enough evidence to show how well the two types of diet work in the long-term, and what the effects are on people's health, for example their cholesterol levels.
In addition, it's been recognised that weight loss programmes are better if they include some
support to help people make changes to their eating and exercise habits. This is often called behavioural therapy, because it works through changing people's behaviour. Group support also seems to help.
A new study has compared people who followed a weight-loss programme over two years, all of whom had behavioural therapy. Half the people followed a low-carb diet (where they could eat as much as they liked, but were only allowed small amounts of carbohydrate – just 20 grams a day at the start of the study), and half followed a low-fat diet (where they were limited to between 1,200 and 1,800 calories a day, only one-third of which could be from fat).
The researchers measured people's weight after two years, and also other factors such as cholesterol levels, blood pressure, bone strength, and body fat percentage.
What does the new study say?
People on both diets did equally well in losing weight. After two years, they had lost on aver
age 7 kilograms (just over a stone), or the equivalent of 7 percent of their body weight. This amount of weight loss is enough to have positive effects on the health of overweight people.
There were few differences in the other health measures. The group who'd had the low-carb diet had much better levels of 'good' (HDL) cholesterol than people on the low-fat diet.
How reliable are the findings?
This was a well-run study, looking at 307 people with a body mass index of 30 to 40 (classed as obese). Quite a lot of people (77) dropped out of the study, which makes the final weight loss results slightly less reliable.
However, people were equally likely to have dropped out of either diet group. So, the results comparing the effects of the diets are likely to be reasonably reliable.
Where does the study come from?
The researchers were from the University of Colorado Denver, Denver, Colorado; Washington University, St. Louis, Missouri; and the University of Pennsylvania, Philadelphia, Pennsylvania. The study was published in the medical journal Annals of Internal Medicine. It was funded by the US National Institutes of Health.
What does this mean for me?
If you need to lose weight, this study shows that low-carb and low-fat diets are likely to work equally well. You may find it easier to lose weight as part of a supervised weight-loss programme that can help you break bad habits and make healthy changes to your diet and lifestyle.
It isn't clear how important the difference in 'good' cholesterol is, because the study didn't measure long-term results, such as whether people went on to get heart disease. However, higher levels of HDL cholesterol are usually linked to better heart health.
What should I do now?
If you are concerned about your weight, you can make an appointment to see your GP. He or she can tell you how much weight you need to lose, and may be able to recommend a local programme to help you.
什么是我们已知的？
寻求助人减肥的饮食要回到几十年前。而在近几年里，低脂饮食相对低碳饮食而言，其优点已被多次讨论。
研究表明低碳饮食对短期减肥效果良好，但尚无证据表明这两种饮食的长期效果及对人体健康如对胆固朜水平的影响。
此外，人们认为有助于改变人们的饮食和运动习惯的减肥项目更佳。这种减肥方法常被称做行为疗法，因为它是通过改变人们的行为来减肥。团队支持似乎也很有用。
一份新的研究对就一个减肥项目进行了 两年之久的人做了比较，这些人全都用过行为疗法。半数人采取低碳饮食（这让人们随心所欲地吃，但只能摄入少量碳水化合物－研究开始时一天仅可摄取20 克），半数人采取了低脂饮食（一天只限1200到1800卡路里，仅三分之一的人顺利减肥）。
研究人员两年后测试了这些人的体重，同时还测试了别的一些身体系数如胆固朜水平，血压，骨强度及体脂百分数。
新的研究告诉我们什么？
两种饮食方法在减肥上的作用相同。两年后，研究对象平均减肥7公斤（这结果不太令人满意），或者说减掉的重量相当于人体重的百分之七。所减少的体重对肥胖者的健康而言却有着积极影响。
在另一个健康测试中结论存在些许差别。较之采取低脂饮食的人来说，接受研究的人中，采取低碳饮食的人HDL胆固朜水平更佳。
这些发现可靠吗？
该研究进展顺利，看到307名研究对象的体重指数在30到40之间（按肥胖等级分类）。相当一部分人（77）退出了实验，这让最终的减肥结果稍有偏差。
然而，两个饮食小组的研究对象都可能退出实验，因此，对饮食减肥法进行比较后得出的结论似乎较为可信。
研究源自何处？
研究人员来自科罗拉多丹佛大学，华盛顿大学，圣路易斯大学，密苏里大学及宾夕法尼亚，费城的大学。研究刊登在医学杂志美食低碳减肥食谱大全视频<<内科年鉴>>上。该杂志由美国国家卫生研究院创办。
该研究于我意义何在？
如果你需要减肥，该研究会告诉你低碳与低脂饮食同样凑效。你也许会发现，参与到一个受监督的减肥项目里，有助你打破坏习惯且能使你的饮食和生活方式得到健康改变，这样更易于减肥。
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