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  #1   ^
Old Wed, May-02-18, 07:47
teaser's Avatar
teaser teaser is offline
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Default Food for thought: Ketogenic diets reduce athletes' anaerobic performance, study finds

Of course the punchline is, it's a four day study.

Athletes who turn to ketogenic diets to help their performance in high-intensity, short duration sports may want to think again, according to new research from Saint Louis University.

In a small study, Edward Weiss, Ph.D., associate professor of nutrition and dietetics at Saint Louis University, together with SLU graduate students Kym Wroble, R.D. and Morgan Trott, R.D., examined the exercise performance of 16 men and women after following either a low-carbohydrate ketogenic diet or a high-carbohydrate diet for four days. His team then tested the anaerobic exercise performance of the participants.

The research team found that after following the ketogenic diet, the participants did not perform as well at the exercise tasks.

"In popular discussions, the term 'ketogenic diet' often is used as a broader term for low carb diets, including Atkins," Weiss said. "However, the language is often confused. People often think low carb and high protein. This is related, but different, as protein can only be at normal levels for a true ketogenic diet.

"The objective of a ketogenic diet is to starve the body of carbohydrate. If there is too much protein in the diet, the body will use the protein to make carbohydrates, which defeats the purpose. When the body is sufficiently deprived of carbohydrate, it manufactures ketone bodies as an alternate fuel. It's an emergency backup system that allows us to survive when we are at risk of starvation. But, it has side effects.

"Right now in the general public, it's touted for weight loss. Some studies have shown that it is effective for weight loss. I worry, though, that this may be a lot of smoke and mirrors. A typical diet is 60 percent carbohydrate. So, if you limit carbs, you might find yourself just not eating that much. If you eliminate most food options, you may just be losing weight because you are cutting calories."

The study has implications both for those who turn to ketogenic diets for weight loss and for athletes who aim to improve their performance.

"The energy metabolism system that's affected is anaerobic. Watching the summer Olympics, the 100 meter sprint and the triple jump depend on this system. You might say that this doesn't relate to me. But for someone with low fitness, they use this same metabolism to get up the stairs. Everyday people use this kind of metabolism without realizing it. This study shows that this energy system is compromised by this type of diet."

Weiss has one caveat.

"There are populations that a ketogenic diet may benefit," Weiss said. "For example, patients who have epilepsy benefit from this diet. For those with abnormal cell metabolism that causes seizures, causing cells to feed on ketones instead can be helpful."

The bottom line?

"Short-term low carbohydrate, ketogenic diets reduce exercise performance in activities that are heavily dependent on anaerobic energy systems," Weiss reports. "These findings have clear performance implications for athletes, especially for high-intensity, short duration activities and sports.

"This diet is especially hot among people who are trying to optimize their health. What this study tells me is that unless there are compelling reasons for following a low-carb diet, athletes should be advised to avoid these diets."

I wouldn't claim that going keto is a good idea for an olympic sprinter, I have no idea. Glycolytic exercise is glycolytic, I haven't seen anybody deny this in any way that I'd take seriously. The Bear used to say some weird stuff about muscle never really using glucose for energy, but rather using it to make fat to use for energy, that's in the category of not to be taken seriously.

Keto dieters do have muscle glycogen, I don't think it's that obvious that they'd all do worse than if they were on a higher carb diet. If we take these researcher's word for it that this study to show whether keto reduces anaerobic capacity was necessary, then since this study wasn't long enough for proper adaptation to the diet, the question must still be up in the air. Given that keto vs. exercise doesn't have a vast literature behind it, it's unlikely that anything near a diligent look at the existing data would fail to acquaint the researchers with the contention that adaptation to the diet is necessary before making any claims about longer-term effects on performance. Heck, they should know this from non-keto dietary intervention studies. So they know about this and don't care, or don't and are negligent. Or maybe they know about it, but it's easier to get a grant for a useless four day study than it is for a longer, relevant study. Too cynical? I wish.

There's also the question of effects on body composition. If you look at anaerobic exercise like a benchlift, drop 15 pounds from a weight where you can only do 1 rep, and maybe you can do 5, or 10 reps. Ordinary people might access this system just climbing stairs, so it is important as they say, but even a small weight loss should decrease stair climbing fatigue, sprint speed etc.
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  #2   ^
Old Wed, May-02-18, 17:03
M Levac M Levac is offline
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If we're familiar with high intensity interval training, we may be aware of its effect on aerobic capacity as well. HIIT is basically an anaerobic challenge. Ironically, the greatest improvement is with aerobic capacity.

The point here is that the belief that some activities rely on anaerobic capacity is in fact incorrect. HIIT can be seen as the activity most dependent on anaerobic capacity, so why does it improve aerobic capacity more than other activities believed to rely on aerobic capacity (therefore train this capacity), i.e. low intensity long duration?

The anaerobic/aerobic premise is flawed. All activity relies primarily on aerobic capacity.

This ain't what's going on with short term ketogenic challenge. Instead, it's likely some adaptation - a shift - of a different set of mechanisms and pathways needed to digest, absorb and metabolize fundamentally different substrates - carbs vs fats, glucose vs fatty acids. In chemistry, this would be like swapping out all the base chemicals we don't need, and put in all the chemicals we actually need. In chemistry, this is easy, it's just a bunch of vials and bottles and whatnots, just plug and play, get running next day. In biochemistry, the "chemicals" must be made on site. This takes time. During this transition period, output invariably suffers. Once adaptation is complete, output goes back up. 4 days is right smack in the middle of this period, where output is at its lowest. There's a great analogy with an oral glucose tolerance test, where we don't measure before the 2 hour mark, where blood glucose would certainly be sky high, where it would clearly indicate diabetes, if we were just retarded enough to conclude that.
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  #3   ^
Old Fri, May-04-18, 07:07
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WereBear WereBear is offline
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Athletes who turn to ketogenic diets to help their performance in high-intensity, short duration sports

Well, excuse me, but my stupid detector just went off.

Sure, study ketogenic diets for four days in a sport that relies on glycogen storage, and declare you have found a bad thing.

Don't make me HULK OUT.
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  #4   ^
Old Fri, May-04-18, 18:25
M Levac M Levac is offline
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Counter-point, without all my usual opinionated BS:
Effects of a short-term carbohydrate-restricted diet on strength and power performance.

The purpose of the study was to examine the effects of switching from a habitual diet to a carbohydrate-restricted diet (CRD) on strength and power performance in trained men (n = 16) and women (n = 15). Subjects performed handgrip dynamometry, vertical jump, 1RM bench press and back squat, maximum-repetition bench press, and a 30-second Wingate anaerobic cycling test after consuming a habitual diet (40.7% carbohydrate, 22.2% protein, and 34.4% fat) for 7 days and again after following a CRD (5.4% carbohydrate, 35.1% protein, and 53.6% fat) for 7 days. Before both testing sessions, body weight and composition were examined using bioelectrical impedance analysis. Three 2 2 multiple analyses of variance were used to compare performance variables between the habitual diet and CRD. Subjects consumed significantly fewer (p < 0.05) total kilocalories during the CRD (2,156.55 126.7) compared with the habitual diet (2,537.43 99.5). Body mass decreased significantly (p < 0.05). Despite a reduction in body mass, strength and power outputs were maintained for men and women during the CRD. These findings may have implications for sports that use weight classes, and in which strength and power are determinants of success. A CRD may be an alternative method for short-term weight loss without compromising strength and power outputs. The use of a 7-day CRD could replace weight loss methods employing severe dehydration before competition.

The Kimberly study reports lower Wingate peak power for CRD. The Sawyer study reports higher Wingate peak power for CRD.
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