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Ketogenic Diets: Claims Versus Evidence

Q&A for Session #
Sports Nutrition Symposium 4.0
Friday January 21st, 2022 @ 12 pm CST

Alan Aragon, MS

Alan Aragon, MS
This presentation will examine the most common claims about ketogenic dieting on fat loss, muscle gain, and exercise performance. Practical applications will be drawn, based on the current scientific research evidence.

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  • Are you aware of any strong evidence to support the claim that ketones themselves have a number of health benefits? This claim has resulted in more interest in increasing ketones exogenously (such as through MCT powders) to reap the claimed health benefits of higher levels of ketones in the body but without actually following a ketogenic diet. Curious if there is any evidence to validate this strategy?
    • The majority of research shows either no effect or actually an ergolytic or performance decreasing effect of exogenous ketones. So they are a very bad bet and I would steer clear from a performance standpoint. The data that show that it does work is very unreliable, I am skeptical of it. The majority of the studies on this topic show no effect or in fact, ill effects.

  • Would love to know the difference between men and women on keto?
    • Not that we know. Men and women differ in their substrate oxidation during exercise so women have a greater amount of intramuscular triglycerides so they actually oxidize/burn more fat for fuel, more so than men. So I don't know if we have the data to say how ketogenic diets might affect any kind of difference in performance between men and women.

  • Are there any health conditions where a ketogenic diet would be contraindicated, especially for an athlete? Such as type 1 diabetes and risks for Diabetic ketoacidosis?
    • It would be rare to incur ketoacidosis. Clinically, the main thing that I would think about is if somebody has known hyperlipidemia or dyslipidemia, you would need to be very careful about the fat sources. Instead of ribeye and butter being your main sources, you might want to consider keeping the "healthy fats" i.e. olive oil, avacado oil, nuts, and seeds. These sources should predominate the fat component of the diet instead of fat coming off of your steak because that can only exacerbate dyslipidemia.

  • Can you clarify where the initial increase in fat oxidation is coming from when beginning a ketogenic diet?
    • The ingestion of fats is a major source. During the course of the day you are in the fed state for most of the day and when you have exogenous substrate coming in, then you are going to be eating more fat, therefore using more fat/oxidizing more fat in circulation. A lot of it is just that 60-80% of your diet is ingested fats. That is where the fat burning comes in.

  • You mentioned <50 g CHO or <10% of total kcal intake to achieve nutritional ketosis - total CHO or net CHO intake (subtracting sugar alcohols and fiber)?
    • Good question. Generally speaking we are talking about non-fiber carbs. There's a little technicality here: Fiber has a of couple calories per gram. So you are still going to get metabolizable energy out of fiber it's just that it will just be about half, at most, of the metabolizable energy you are going to get from a gram of CHO. If you are someone who eats an extraordinary amount of fiber you will still get metabolizable energy but to simplify the question more, it leans more toward non-fibrous carbs.

  • Can you break down the statement/ claim "Fat burns in the flame of carbohydrate"? If you are attempting to go on a Keto diet, what is caveat that enables fat to burn with reduced carb intake? May y0u recommend a pyruvate supplement to help with this if you are limiting Carb intake?
    • So that statement is a misapplication of biochemistry. Fat burns in the flame of an energy deficit (body fat in particular). Dietary fat burns in the flame of increased dietary fat. That saying is misplaced to begin with.

  • There are some endurance athletes that take 100-200g carbs during their training but still never leave ketosis (as measured). Would this be “best of both worlds” or an unnecessary complication?
    • Circulating ketone levels, ketosis, per say is noise. It depends on goals also. If you're someone who depends on high intensity output either intermittently or through the length of your athletic endeavors, then ketosis would be a red flag/ bad sign to any degree.

  • I don't know what the findings are as far as corisol goes. I have seen studies where cortosiol goes up under phisiologically stressful situations. That would include any kind of dieting. I have seen it elevated in low carb diets. The question would be if there is if there is cortisol flux, how does that influence performance or body composition? When you follow that question to its logical end, it is kind of just noise (background noise). It is almost like the ebb and flow of insulin in high carb low, fat diets versus low carb, high fat diets. The insulin is going to be much higher in the higher carb diets but is that going to influence body fat? It actually doesn't. It's a similar story with cortisol. It is more like a fun thing to speculate about than something to kind of kick around the hard data.
    • I don't know what the findings are as far as cortisol goes. I have seen studies where cortisol goes up under stressful situations. That would include any kind of dieting. I have seen elevated in low carb diets. The question would be if there is a cortisol flux, how does that influence our body composition. When you follow that question it ends up to be just noise. It is almost like the ebb and flow of insulin in high carb low fat diets versus low carb high fat diets the insulin is going to be much higher in the higher carb diets but will that influence body fat? It doesn't. Similar story with cortisol. It is more like a fun thing to speculate about than kick around the hard data.

  • The biggest concerns I see/hear is about KD and increased risk for CVD---have you seen any evidence within athletes on this topic and/or what are your thoughts?
    • That is a great question. The carnivore diet only has one study worth considering. It really only starting getting talked about in 2018-2019. Researchers jumped on the opportunity to post data about the carnivore diet. There is an observational study by LENNERZ and col. (Google Lennerz Carnivore Diet Study). They found that all of the health parameters for people who have been carnives for a couple of years (up to five years or so) - their health all looked great. Every parameter you could think of accept for LDL cholesterol (was elevated) and maybe the more alarming parameter being coronary artery calcium. Out of a huge sample, they only found 15 people who actually tracked their coronary artery calcium score pre-carnivore diet versus mid-carnivore diet. Their scores about doubled! That is worrisome about coronary artery calcium accumulating. There are data showing that eating meat, animal foods, with the addition of fresh fruits and vegetables has shown a protective effect, almost a neutralizing effect. The totality of data we have, going carnivore and avoiding plant foods indefinitely is at best not optimal and at worst a severe CV risk in the long-term. If you wanted to carnivore more safely, mix in low-fat meats, trim the fats off of your meats, with the exception of fatty fish. Improve it even further by simply adding in the "healthy plant-based fats" i.e. olive oils, avocado, nuts, etc. And of course fiber-rich, whole plant foods like vegetables and fresh fruits.

  • Do you need to replace more water electrolytes on keto?
    • According to Jeff Volek You Do. According to Jeff Volek you end up excreting more sodium just as a result of the mechanics of dropping carbs out of the diet. His method was to make sure you have a bouillon cube every day. Most people salt food anyway, the guideline for ketogenic dieting would be to not skimp on salt. I'm not aware of any formal data of people going into dangerous low sodium levels when they get on Keto and anecdotally it hasn't been much of an issue. Most people who get on Keto are coming off a standard western diet which heightens the saltiness of their palate and they won't put up with bland keto anyway. The potential to increase sodium dietarily I dont think most people have to consciously worry about, most people anyway.