In the World of nutrition, not everyone shares the same opinion (obviously). And perhaps the most stark and common example of this concerns the relative amounts of carbohydrate and fat we should have in our diets. The conventional view is that the diet should be, generally speaking, low in fat and high in carb. Fat, we are told, makes us fat, so eating less of it is the sure-fire way to keep lean and healthy. On the other hand, some argue that it’s not too much fat that makes but, but too much carb. Such individuals will advocate a low-carb diet, which may (but may not) end up being quite rich in fat.
Variously on this site I have referred to studies which, overall, show that low-carb diets outshine low-fat ones in the weight loss stakes. I’m not aware of one single study, as it happens, which found a low-fat diet to be superior in this respect. Those that cling to the idea that low-fat is the way to go, will very often resort to claiming that low-carb diets are unhealthy, often on the basis that their sometimes high fat content will put people at risk of cardiovascular diseases such as heart disease and stroke. I have to say I’m unmoved by this argument for two main reasons.
Firstly, there really isn’t very much evidence linking supposedly unhealthy saturated fat (found mainly in meat, eggs and dairy products in the diet) and increased risk of cardiovascular disease. Neither is there much (if any) good evidence that eating less saturated fat has broad benefits for health.
But my other major issue with the argument that low-carb diets are bad for the heart and circulatory system is that studies have found that such diets generally lead to improvements in biochemical markers of cardiovascular disease compared to low-fat diets. Many studies, for instance, have found that lower-carb diets have led to changes in blood fat levels that would be expected to lead to a reduction in cardiovascular disease risk.
I was interested to read of a study published very recently which sought to review the evidence in the area . Thirteen studies in which low-carb diet were pitted against low-fat ones were included in the review, and each of these lasted at least 6 months. One limitation of the study was that the design of the low-carb diets in the individual studies sometimes allowed reintroduction of significant amounts of carbohydrate.
Despite this, the results showed that compared to the low-fat diets, the low carb ones had generally favourable outcomes. These included:
Significantly more weight loss at 6 and 12 months (about 4 and 1 kg respectively)
Significantly lower triglyceride levels
Significantly higher ‘healthy’ HDL-cholesterol levels
The low-carb diets had lower attrition rates too, suggesting that individuals have a harder time sticking to a low-fat diet compared to one that is carb-controlled. This is important, seeing as compliance is important if the benefits of any diet are to be sustained.
This review does a good job of assessing the relative benefits of lower-carb and low-fat eating. And it shows, once again, that as a general rule, the former is preferable for the purposes of weight loss and bring superior benefits in terms of cardiovascular risk factors too.
1. Hession M, et al.Systematic review of randomized controlled trials of low-carbohydrate vs. low-fat/low-calorie diets in the management of obesity and its comorbidities. Obes Rev. 2008 Aug 11. [Epub ahead of print]