Lower body fat = better climbing. It’s an equation that’s been around since the sport’s inception. Modern climbers try intermittent fasting or starvation techniques to lose weight before trips to get the send.
Recently, the keto diet has gained traction among the climbers desperate for an edge.
The ketogenic diet, eating high fat and low carb foods, has been hailed as the next secret sauce to becoming a skinnier, stronger, healthier superhuman. The goal of the diet is to put the body in a state of ketosis, which essentially means to make the body better at metabolizing fat.
When fat is metabolized, the byproducts of that process, ketones, are used for fuel in place of glucose (produced for energy from carb consumption). Fat metabolism occurs either during starvation or by restricting both carbohydrates and protein.
Promoted on a ketogenic diet are free oils, particularly butter, ghee, or coconut oil, eggs, meat, cheese, nuts and vegetables.
Sound too good to be true? Can a keto diet help performance, can it actually help us lose more weight, and, most importantly, is it actually healthy?
Increasing Performance on Keto
Muscle cells are equipped to metabolize ketones for energy, as are most other major organs in the body. Red blood cells, however, lack the necessary cell structures for ketosis and can therefore only generate energy with glucose. Red blood cells will die if blood sugar levels are not maintained.
Where does this sugar come from if you aren’t eating carbs? On the keto diet, sugar seems to come mostly from the conversion of the moderate protein consumed or from protein from your own muscle tissue. With this in mind, let’s examine some studies.
Few studies have examined keto in the context of muscle building and performance, however, those that have are not promising. For example, in a 2018 study, young, normal-weight men underwent an eight week training program and were assigned to one of three groups: a keto diet group (<10% carb; 20% protein and 70% fat), a non-keto group (55% carb; 20% protein and 25% fat) and a control group, which were not assigned a dietary regimen. The diets were designed so that they met the subjects’ daily calorie needs. After eight weeks of resistance training, those on the keto group lost more fat than the other groups. With regard to muscle mass though, the non-keto group and control diet group gained over 2 lb of muscle, however, the keto group did not gain any muscle whatsoever despite eight weeks of rigorous training, and trended towards a decrease in muscle mass, although this was not statistically significant (meaning likely no change vs true muscle loss).
I mentioned that there must be a steady supply of glucose in your bloodstream to maintain your red blood cells. If you are not going to eat the carbs then your body will derive it from protein. Despite eating 2 grams per kilogram of protein per day (~160 g of protein per day), those eating the keto diet were still unable to build muscle. In other words, protein utilization was going towards making enough sugar to sustain the body and it was not contributing to muscle growth. A loss of lean muscle mass in the legs was also observed in a separate 3-month pilot intervention in those doing crossfit and a keto diet compared to a control diet.
As observed in other studies, a keto diet tends to increase fat oxidation (fat being used for energy). Fat requires much more oxygen for breakdown, and likewise oxygen uptake, or VO2 max, is typically increased. This actually results in an inherent issue with the ketogenic diet. The body cannot fully compensate because much more oxygen is needed to derive energy. This can be observed in several studies. For example, in a recent study examining the effects of a keto diet on high-intensity, short-duration exercise (which may translate to bouldery sport routes), subjects were placed in one of two dietary groups (high-carb vs keto). After four days on the keto diet, peak power was reduced by 7% and recovery was reduced by 15% compared to the high-carb diet.
Many would say that four days is too short to gain “fat adaptations” and for your body to “catch up”. But in fat-adapted elite race walkers (endurance-based exercise), due to the high oxygen demands of a ketogenic diet, those consuming the ketogenic diet did not benefit from three weeks of intensive training and actually performed worse in their races compared to the high-carbohydrate groups.
Based on the scientific evidence and what we know about metabolism, consuming a ketogenic diet is likely not helpful for gaining muscle mass or improving performance compared with higher carbohydrate diets. As detailed by a critical review, if one is trying to gain muscle, eating a diet which meets calorie needs and is healthy is sufficient to do so, while eating keto is counterproductive in this regard.
Decreasing Fat on Keto
Most people who go keto are doing so to lose weight. Several studies with unrestricted intake of food have demonstrated that a ketogenic diet can indeed result in fat loss (here and here for example), including some of the studies mentioned above. However, the question is not whether restricting carbs results in weight loss, the more interesting question is, all things being equal, is restricting carbs as effective as restricting fat or not? Very carefully controlled studies, called metabolic ward trials, have investigated this question.
While this study did not look at a ketogenic diet specifically, it still looked at high-fat (50% of total calories) vs low-fat diet (~7% of total calories) keeping all other variables equal. What was found was that a low-carb (keto) diet resulted in more weight loss, but a low-fat diet resulted in more fat loss.
While these changes seem insignificant (the study was only six days), metabolically this is a large and significant change, as the low-fat group burned ~70% more fat than low-carb (keto) group. The low-carb group lost 53 grams of fat per day while the low-fat group lost 89 grams per day. The question is, what accounted for the greater loss in body weight in the low-carb group if it wasn’t all fat? This was due to loss of muscle mass, primarily due to water loss from depleted glycogen storage (how carbs are stored) as well as some degree of muscle breakdown as indicated by increased urinary nitrogen. A review of metabolic ward trials is in agreement with these findings.
Is Keto Healthy?
Any diet aimed at weight loss or increasing strength should also be healthy—there is no point to losing weight if we are sickly and promoting chronic disease. So how does the keto diet impact long term health?
In a recent study examining young, healthy subjects who either consumed a keto diet or a baseline, regular diet (15% protein, 50% carbohydrate, and 35% fat) for four weeks, both cholesterol and inflammation shot up eating keto. This tells us that heart disease was being promoted (inflammation underlies all chronic diseases) with the keto diet. Further, after four weeks, when those on a keto diet ate a meal from the baseline diet (50% carbs vs 5% carbs), their blood glucose and insulin rose way beyond normal, indicating they were insulin resistant. This means that their muscles were ineffective in utilizing carbohydrates for energy.
As climbers, we typically don’t have to worry about diabetes (type 2 diabetics are insulin resistant), however, it is problematic if our muscles are ineffective in utilizing all forms of energy, (indicative of what we saw earlier with decreased performance). In muscle cell studies (examples: here and here), muscle cells treated with the dominant type of fat found in keto diets (a type of saturated fat called palmitate) were severely impaired in making energy.
The very components of a ketogenic diet (copious saturated fat, primarily from animal fat, and a restriction of carbs) have been well studied. Based on what we know from every level of nutrition research (cell, animal and human studies), you would essentially consume the very opposite of a ketogenic diet for optimal health.
In one of the most comprehensive reviews to date on carbohydrate intake and mortality from all causes (death rates), those consuming the lowest amount of carbs have shorter lifespans.
The authors also noted that those consuming high-carb diets had shorter lifespans, however, this was tightly dependent on the type of carbs, and when unprocessed carbohydrates (e.g. whole grains) replaced processed carbohydrates, lifespan was increased. Even looking at the Inuit who are one of the few populations who eat low-carb, high-fat out of necessity, they have twice as many strokes and live 10 years less than the rest of the population. There is essentially no population model which indicates a low-carb, high-fat diet is beneficial to health.
A Healthier Way?
When I hear people say they are going low-carb or keto, what I really hear is, “I am restricting plants,” because carbohydrates are mostly plant-derived. Not a single study exists which demonstrates that beans, whole grains or fruits, all very rich carbohydrate sources, worsen your health. In fact, those foods are clearly linked to a longer life span and reduced chronic disease risk. A diet which maximizes these carb heavy foods, such as an unprocessed plant-based diet, is the only diet ever demonstrated to reverse heart disease (examples here and here), reverse prostate cancer, and on a population level, plant-based diets are linked to increased lifespan by several years (here and here).
With regards to weight loss, eating more foods of plant-origin will inherently result in weight loss assuming they are in their intact, unprocessed forms. Based on the principles of calorie density for example, it is essentially impossible to gain weight eating fruits because they take up so much stomach volume but contribute few calories for that space. Many would find it shocking to consider fruits as a weight loss food, but when subjects went on an unrestricted high-carb, plant-based diet (70% carb), they actually lost over eight pounds of fat after 16 weeks.
With regards to muscle building, one of the most comprehensive reviews on protein and muscle protein synthesis finds that as long as calorie and protein needs are met through dietary means, you will have sufficient protein for muscle synthesis (keto seems to be an exception based on what we discussed). Essentially, unless you’re starving or eating a strict fruitarian diet (fruit only diet) it is extremely difficult to not meet/exceed protein needs.
The desire to be healthy, fit and strong drives us all as climbers, and nutrition is a major component of this overarching goal. With all of the seemingly conflicting information out there, however, both in the media and anecdotally, it is hard to discern between what is legitimate and what is not. As someone who is involved in nutrition science, not just reading studies, but also conducting a variety of studies, from cell, animal and human, I can tell you an important observation: nutrition science is rarely conflicting. Nutrition science is complex and the methodology of studies can often pre-determine the outcome. This is a big reason why industry sponsored studies favor industry’s interests. When I read studies, I don’t just read the conclusion, I skip everything and go to the methods and results section, as this is what will drive the author’s conclusions. When all this is taken into account, studies rarely conflict.
In summary, consuming a ketogenic diet is a poor strategy if one hopes to not only perform optimally, but also be healthy. While yes, a ketogenic diet can elicit weight loss, other dietary approaches that are higher in unprocessed carbohydrates can also elicit fat loss even more effectively and promote health. Eat carbs and climb harder!