A battle rages! Some say it’s a battle as old as time. A battle at least as old as all living memory. One side is lead by house Low Fat, High Carb and the other is lead by house Low Carb, High Fat. Is this a valiant fight to find the best army to save humanity from the evil power of disease and obesity, or is it a waste of precious time while evil powers destroy us all???
Clearly I have been reading too much Game of Thrones! But I digress. There is definitely a great debate in the health and nutrition industry between what type of diet is best for weight loss/management, low carb or low fat. There seems to be evidence for both sides with government recommendations and mainstream professionals favouring low fat, high carb and alternative practitioners and those who stay current with new research favouring lower carb, higher fat. But what is the answer? My opinion is that it is an individual thing, although I would almost always lean towards a lower (around 20% of calories) carbohydrate diet with appropriate amounts of fat and carbohydrate to fuel activity and vitamin/nutrient density. That being said there is a number of other dietary factors that need to be considered aside from simply carbs or fat (ex. vitamin/mineral content, carbs from grains or roots/vegetables, carbs from refined sugars, carbs from fructose, Omega 6:3 ratio, processed food intake, etc). Basically, it is not as simple as saying to everyone: “eat low fat or eat low carb”. Sorry to burst everyone’s bubble!
Notwithstanding the above, a recent scientific paper was published in the Journal, Cell Metabolism, indicating that a low fat, high carb diet leads to greater fat loss than a low carb diet. Obviously, media types and such go nuts over this stuff, so this post is meant simply as a review of the noted study and whether we should heed the results or not.
High Carb Study Overview
The study included 10 male and 9 female overweight individuals and had them eating either a lower carb, higher fat diet or a low fat, high carb diet. One of the strengths of this study was that it was a controlled dietary trial, meaning that it was an in-patient study where the participants spent the duration of the study in a metabolic ward. Basically, all food and activity was strictly regulated by the researchers. Therefore, there is no need to worry about issues with people not following the outlined diet or inaccurately recalling what they ate. The participants had 2 stays of 2 weeks in the metabolic ward with a 2-4 week period between visits. To get baseline measurements, during the first 5 days of each 2 week stay, the participants were fed a diet consisting of 50% of calories from carbs, 35% fat and 15% protein. Total caloric intake for the first 5 days was approximately 2700 per day. For the remainder of the 2 week periods, the participants were put on a 1900 calorie per day diet that was either low fat (71% carbs, 8% fat, 21% protein) or low carb (29% carb, 50% fat and 21% protein). During the 2 weeks a number of metabolic markers were measured including fat and carbohydrate oxidation (what fuel was being burned for energy), body fat, weight, insulin release, and a large number of standard blood panel tests (cholesterol, etc.). The main reported results of the study was that the group on the high carb, low fat diet lost more fat mass than the low carb, high fat group. However, to put this into perspective, the difference in fat loss between the high carb and low carb group was 110 grams over the course of the 4 week study, that is approximately 0.2 pounds. While the researchers indicate that this is statistically significant, from a mathematical standpoint, given the small sample size, I would be interested to see what a similar study on another 20 participants would find. On the other hand, the low carb group lost 505 grams more total weight compared to the high carb group. While fat loss is more important to health than total weight loss, the results are still interesting. Overall this is an interesting, high quality paper; however, there are some things that are not specifically addressed in the study results and commentary that need to be considered when determining what type of diet is ideal.
High Carb Study Does Not Paint the Full Picture
Surprise, surprise, a study implementing 2 different calorie reduced diets found that both diets lead to weight loss and fat loss. Whether you believe it or not, calorie amount matters with respect to weight loss; although, I would rather refer to it as “food amount”, not calories. Basically, whether you eat too much steak or too much bread you still won’t lose weight, maybe. However, here is something else to consider. What would happen if we had the same study design as the above but instead of the 2 diets being low calorie, they were non-calorie restricted? Would the high carb diet still show favorable changes in body fat composition or would the low carb diet be the winner? I would bet on the low carb, high fat diet. Taken one step further, what if the 2 diets were excess calorie, would the high carb diet preserve health or be detrimental? Probably detrimental given the evidence linking high glycemic load and index diets to poor health. Interestingly, there is evidence that a low carbohydrate diet can improve diabetic markers even when there is no caloric restriction (1). Specifically, the referenced study found that a low carb, non-calorie restricted diet, compared to a calorie restricted higher carb diet, lead to improvements in blood sugar control as well as a markers of cardiovascular disease risk.
Some other considerations regarding this study is that the number of participants (19) is very small and they are taken from a specific portion of the population, obese people. Therefore, we cannot simply take these results as fully applicable to the non-obese population. Another consideration is that is it a short study, only 4 weeks consisting of 2 periods of 2 weeks. Furthermore, given that the first 5 days of each 2 week period consisted of a “normal” diet, the dietary intervention actually only occurred for 18 days total. Granted, it is not very easy to coop people up for 6 months in a metabolic ward to experiment on them, so the researchers probably did the longest study they could with the resources they had and the ethical standards they had to follow. That being said, we have no idea what the results of these 2 diets would have been if the study was extended to 6 months or a year; thus, the results cannot be applied to dietary interventions that are planned for longer than 9 days (the study had 2 periods of a 9 day diet intervention).
There are also 2 things I would like to touch on with regards to the actual low carb diet used in the study. First, the low carb diet intervention contained 30% of calories from carbohydrates. While this is technically considered a low carb diet, it does not near the range of a very low carb or ketogenic diet. The importance of this is that we know ketogenic diets have also been associated with positive changes in body weight and health markers in obese and metabolic syndrome individuals. So, would a high carb diet outperform a ketogenic diet with regards to fat loss? Actually, the researchers themselves mention that if the carbohydrate content was reduced to a ketogenic level it may have related to more fat loss than seen with the low carb diet used.
Second, we know that the dietary omega 6:3 ratio of our western diet is much higher than that our ancestors and this is causing some major health concerns in our population (2). Unfortunately, the Omega 6:3 ratio of the low carb diet was approximately 7:1, much better than the normal population but much higher than the ideal 2:1 or 1:1 ratio. Aside from being important for general health, is this important for fat loss? Maybe, since we know that obese and people with metabolic syndrome often have higher levels of inflammation and a high Omega 6:3 is associated with high levels of inflammation. But, it wasn’t measured in this study.
High Carb vs Low Carb and General Diet Considerations
Not surprisingly, the results of the reviewed study indicate that yes, amount of food matters for weight/fat loss arguable just as much as macronutrient percentage; however, there is more to consider in determining an appropriate diet than just weight/fat loss.
Reducing the risk of other medical conditions: Most studies looking at calorie reduced low carb diets in obese, diabetic and healthy individuals find similar results for weight loss in comparison to high carb diets, but where the low carb diets differ is in the reduction of other risk factors such as cardiovascular disease, diabetes, neurological disorders, cancer, inflammation, acne, and epilepsy (1, 3, 4, 5).
Diet Compliance: It’s all well and good if for 9 days someone can stick to a reduced calorie, high carb, very low fat diet and lose fat, but what about when they need to stay on said diet for a year to reach a healthy weight? Is it easier to stick to a low carb, high fat diet, or the alternative. We also need to consider whether people can even stick to a reduced calorie diet for a long period of time, and whether that is even healthy from a micronutrient intake perspective, which brings us back to whether a non-reduced calorie low carb diet would lead to greater weight loss than a non-reduced calorie high carb diet, while maintaining appropriate vitamin/mineral intake.
I found a few studies that indicate that low carb diets may be better in the long term with regards to quality of life and weight maintenance. Once study (6) found that after 1 year on a low carb or low fat diet, diabetics reported better quality of life when on a low carb diet. Another study (7) found that in healthy men, a lower (50%) carb, low glycemic index (GI) diet was better at maintaining weight loss when a refeeding period was included after a reduced calorie weight loss period. Basically, after losing weight on low calorie diets, participants switched back to an excess calorie diet (like when you go off a diet in real life) and where better able to maintain their weight loss if the excess calorie diet was lower carb and GI.
Furthermore, there seems to be evidence that study participants prefer low carb vs high carb/low fat diets (8). This could be due to a number of reasons such as taste of food, nutrient density of food, and satiety. Unfortunately, I couldn’t find any studies specific to hunger levels of participants on a low carb vs high carb diet, but there is plenty of testimonials around the internet of people being much more satisfied on a higher fat/low carb diet than a high carb one.
Nutrient Deficiencies: One further consideration is nutrient density of high carb, low fat diets. This could also play into most people’s lack of ability to comply with a high carb low fat diet for a long period of time. Traditionally, high carb diets are low fat diets and run the risk of vital nutrient deficiencies, particularly: fat soluble vitamins (A, E, D, K2, K), vitamin B12, choline, iron, zinc, and essential fatty acids (mainly Omega 3: EPA/DHA).
High Carb Diet Study Takeaway
To wrap up this long post, I do not want to take away anything from the study itself or its results. They seem accurate for what they are. Mainly, a calorie is a calorie…or…amount of food actually matters most when it comes to weight/fat loss in the context of a calorie restricted diet. However, in light of the above, it is clear that the study does not address many of the other factors we need to consider when determining if low carb or high carb is best. This includes, what is best for long term weight loss/maintenance, what reduces the risk of diseases the most, what improves standard of living the most, what is easier to maintain long term, and what allows for the most micronutrient density intake.
So, my final takeaway is that the results of this study cannot be applied to everyone in the general population, particularly for a period longer than the length of the study intervention (9 days); however, as found in past studies, calorie restriction/eating less food will help you lose weight…although it may not be the best option for ideal health.
The Barefoot Golfer