There has been a general trend over the last several decades wherein the populace and nutrition based media propogates low-fat diets, demonizing fats and portraying a low-fat diet as the key to weightloss, this is followed a few years later by a switch to a focus on low-carb diets, again followed by a switch back to low-fat after another few years, etc. In this blog post, I will focus on the low-fat diet, and why "the fat you eat" is not necessarily "the fat you wear."
1. Lack of evidence.
There is a general lack in evidence that a low-fat diet is superior in regards to weightloss. The same can be said for low-carb, according to a 2014 meta-analysis done by Johnston et al., that found no statistically significant differences in weight lost across low-fat and low-carb dieters, leading to a conclusion that if either leads to a reduction in caloric intake, they will lead to weightloss. While fats are the most calorically rich macronutrient, they are a slower releaser of energy that can keep one feeling full for a longer period of time, which can often lead to a balancing out in caloric intake.
2. Poor nutrient absorption.
Many nutrients aren't adequately absorbed when an individual is not consuming enough fats, and this can be a risk of a low-fat diet if one is not careful. Fats are essential building blocks for many molecules and are important for the absorption of fat-soluble vitamins A, D, E and K and carotenoids. Deficiencies in these micronutrients can lead to issues in eyesight, bone and muscle damage, as well as poor cardiovascular health.
3. Unsustainability.
Low fat diets are also notoriously difficult to follow long term, as good flavor often hinges on the use of fats in foods, and therefore is not generally a sustainable diet for many people. Often, with regards to weightloss, the media advertises many "quick-fix" diets like the low-fat diet that an individual will only have to follow for a set, usually short, period of time and once they have lost their desired weight can, in theory, return to their previous way of eating. This more often than not leads to yo-yo dieting, wherein one will gain lost weight back then go on a other quick diet, then gain that weight back once again. Because of this, health professionals generally recommend making a change in diet that will be a permanent one, which necessitates that that diet be one an individual can follow long term or indefinitely.
To elaborate on that last point, if a lower fat diet is one that works for you, and it is sustainable, then it might be a viable option. The choosing of an adequate diet for weightloss, maintenance, or general health-improvements has to be decided on an individual basis, as what works for one may not work for others. However, to reiterate, there is no evidence that a low-fat diet is superior to others. In addition, if one is not carefully observing to ensure that they have adequate fat intake, it can lead to nutrient deficincies. These are all important to consider when deciding what sorts of dietary changes are right for you.
Sources cited:
Johnston BC, Kanters S, Bandayrel K, et al. Comparison of Weight Loss Among Named Diet Programs in Overweight and Obese Adults: A Meta-analysis. JAMA. 2014;312(9):923–933. doi:10.1001/jama.2014.10397
