Ah yes, good old ketogenic (aka "keto") or low-carb diets. Low-carb diets sound like they make sense, right? It only makes sense that the body primarily burns glucose (carbs) as an energy source, so if you eliminate as many of your carbs as possible, then it has to turn to stored body fat stores. Yeah, because human metabolism is easy and straight forward...
Human metabolism is simple, right?
I have attached a fantastic video at the bottom of this blog detailing a study conducted by Dr. Kevin Hall. Dr. Hall completed a study in which he tested the overall effects of a high-fat, low-carb diet. In other words, their goal was to push study participants into a state of ketogenesis to determine if this is an effective form of weight/fat loss.
What he found was that although study participants witnessed a pretty immediate and drastic loss in both weight and body fat, their progress stagnated, or plateaued. There were two other pretty telling markers from this study as well. First, the control group (non-keto) lost just as much body fat as did the low-carb group. Secondly, although both the low-carb and control groups lost equal amounts of body fat, the low-carb group lost more overall weight.
Wait, so the low-carb group lost more overall weight, that is what people want, right? Well, not so fast. Since both groups lost the same amount of body fat but the low-carb group lost more overall weight, that indicates that the low-carb group lost more lean tissue, aka muscle.
What was witnessed in this study, and something that seems to be pretty apparent in most attempts at weight loss (Set Point Theory), is that our bodies adapt. Sure, there was pretty immediate change when first going 'low-carb' for these study participants, but the body became "fat-adapt" and progress slowed. Not only that, but at what cost?
I just recently wrote about how being skinny isn't enough for optimal health. Just because an individual is within a "healthy weight range" does not make them healthier. The human body needs muscle and strength to be able to withstand the rigours of life, meaning a well-balanced resistance training program alongside a healthy diet is the best for lifelong, safe, and effective living.
I have always said that carbohydrates are not only useful, but important for optimal health. Despite getting a bad rap, insulin is an effective tool to not only build muscle, but to reduce muscle wasting (catabolism).
This study found that muscle protein synthesis was slowed on a high-fat diet. In this case, insulin resistance appeared to also cause anabolic-resistance.
This study found that muscle hypertrophy was reduced in mice with high fat diets.
In conclusion, chronic high fat feeding impairs the ability of skeletal muscle to hypertrophy in response to increased mechanical load. This failure coincided with a failure to activate key members of the Akt/mTOR signalling pathway and increase protein translation.
And finally in this study (also a mouse study) found that high fat diets - both 70% and 46% caloric intake, lead to a decrease in muscle protein synthesis.
Do I think that keto diets are effective for weight loss? Yes, actually! I think there is lots of empirical and anecdotal evidence indicating that individuals consuming a low-carb, high-fat diet can lose weight, and in a relatively short amount of time. Not only that, but just as Dr. Hall mentions in the video, keto diets seem to be more satiating to individuals. People report feeling fuller, longer, which may be a benefit if you are trying to lose weight. But again, at what cost?
Having said all of that, I always approach both dietary and exercise goals with the same thought in mind. How realistic is what you're intending on doing? Can it be done for a long term? Is it sustainable? Keto diets can be tough to maintain over a long term, especially for individuals looking to improve strength and performance.
Tyler Robbins B.Sc. CSCS
Director of Fitness
Head of CrossFit