What is the best approach for weight loss: a low fat diet or a carb free diet?
A recent meta-analysis attempted to highlight whether a low fat diet, or carb free diet, was most beneficial for weight loss. This meta-analysis investigated the findings of thirteen other studies, pooled all their results together, and analysed the findings. I’ll discuss the findings of the meta-analysis below.
Traditionally, diets targeting weight loss have tended to promote a reduction in the amount of fat an individual consumes. It is believed that minimising fat in the diet will promote weight loss, largely through the reduction in the overall number of calories the individual is consuming. [It has also been believed that eating fat ‘makes people’ fat – wrongly, of course].
Most recently, however, low fat diet approaches to weight loss have been shunted out of mainstream recommendations in place of low carbohydrate diets or a carb free diet, otherwise known as ketogenic diets. Low carbohydrate diets tend to maintain, or even increase, the amount of protein and fat within the individual’s diet, unlike a low fat diet, and instead target a much more significant reduction in the carbohydrate content of the diet. It has (wrongly) been hypothesised that lowering one’s carbohydrate intake mediates weight loss through the action of insulin. As in the case with low fat diets, low carbohydrate diets – to the furthest extent possible – lead to weight loss through a reduction in overall caloric intake.
But which is better, or, rather, which is most successful?
A study by Bueno et al. 2013 found favourable results for very low carbohydrate ketogenic diets (VLCKD, referred to here as a carb free diet) when compared to low fat diets. The low carbohydrate diets studied tended to promote more weight loss, and they also showed greater declines in diastolic blood pressure, a decrease in triglycerides (TAG), and an increase in HDL. Both TAG and HDL are markers/subcomponents of one’s cholesterol level, and a reduction in TAG and an increase in HDL are considered favourable (with regard to reducing one’s risk for cardiovascular related diseases).
Despite the significant findings, there were some limitations that the authors highlighted. For example, participants in the studies tended to consume far more carbohydrates than were actually being advised. This highlights a very real issue of adherence, or lack thereof: individuals left to their own devices, after nutrition advice, were unable to follow and implement the carb free diet completely – that being said, there was an obvious decline in their carbohydrate intake, from where it was, when placed on a very low carbohydrate diet (just not to the extent recommended).
In addition to the lack of compliance regarding carbohydrate intake, there were a number of participants that dropped out of the 13 studies over their duration, and only a few of studies followed participants for 24 months, with the majority stopping at 12. There is ample evidence to show that weight loss studies tend to show very favourable results at 6 months duration and slightly less so at 12 months. Results rarely improve beyond a year post initiation of the diet, with opposite trends commonplace i.e. people begin regaining weight. Lastly, despite statistically significant results being found, these actually only translate to very minor ‘real world’ changes i.e. a shift on bodyweight of 1 kilo over a 12 month period – considered statistically significant, but minimal real world difference.
In summary, both a low fat diet and a low carbohydrate diet approach to weight loss can be successful. In addition, weight loss advice may be shifted toward promoting low carbohydrates diets as a meaningful way for people to lose weight, and there’s no denying that it provides an effective tool to combat obesity. That being said, compliance appears an issue to a near carb free diet. People should find a diet that works for them, and that they can actually stick too, if long term dietary success is their goal.