Beware of the new contrarian embrace of dietary fat
Some of you may have heard about a new book called The Big Fat Surprise. The basic premise of the book is that fat is not bad for you and that you should eat more of it. When I first heard about this book and recovered from my apoplectic fit, I marvelled at how many times we can keep having the same discussion. Most diets can be lumped into two broad categories of either low-fat or low-carbohydrate diets.
The notion that fat is associated with cholesterol and heart disease goes back several decades with research programs like the Framingham Heart Study and the MRFIT study, and initially led physicians to recommend low-fat diets as a way to stave off heart disease. The problem with this strategy was two-fold. First, as people sought out low-fat alternatives to their favourite junk food, companies simply took out the fat and added more sugar.
Thus they were able to preserve the taste while still being able to label their food fat-free. As you might imagine, this did not translate into health benefits. As a result, most studies of a low-fat diet have been negative, and this fact is proudly proclaimed in the book.
The second problem with the low-fat diet is more subtle. Our understanding of fat and cholesterol has evolved considerably since those early studies. Now we speak of LDL and HDL (bad and good) cholesterol, rather than total cholesterol, as we once did. Also, instead of talking about total fat, we now talk about good fats (mono and polyunsaturated fats) that we get from fish and vegetable oils and bad fats (trans fats) that are present in fried foods. So a problem with the low-fat diet is that people reduced their intake of both good and bad fat, which essentially cancelled out the effects of each.
Admittedly, the evidence for different fat sources is not rock solid. Although it is incontrovertible that smoking causes lung cancer, and that high blood pressure leads to a stroke, trying to prove that good fats are protective while bad fats are harmful is very difficult. There are a number of reasons why nutrition-based research is hard to do, but the main difficulty is that people’s diets fluctuate over time and rarely stay consistent.
The book I mentioned starts by poking holes in the evidence for good and bad fats, which is fair enough because, like I said, it is not perfect. It then goes on to state that sugar and carbs are the real enemy. For those of you who realized that this is essentially the Atkins diet repackaged, congratulate yourselves on an astute observation. Finally, it makes the rather bold claims that we should eat more fat and butter in our diet. This strikes me as a very bad idea.
Although we can say that the evidence on trans fats is not as good as we would like it to be, no reasonable researcher out there is going to claim that they are protective. That is just ridiculous, and eating more trans fats is not going to make you healthier.
Of course we need some fat in our diet, just as we need some carbs and proteins for everything to work properly. I’ve always suggested people should get their fat from fish and vegetable oils rather than fried foods, that they should get their carbs from whole grains rather than sugary treats and baked goods, and they should top it all off with a little bit of protein (either from lean meats, fish, lentils or nuts). I thought about writing a book and calling it the Labos diet, but then somebody told me that it already has a name. It’s called common sense.
Chris Labos MD