Susan Kleiner, PhD, has been a practicing clinical nutritionist in the Seattle area for years, and is also one of the founding members of the International Society of Sports Nutrition. Kleiner has consulted with a number of athletes as well as private individuals and says that based on what she has seen, the keto craze seems to be on its downward curve.
Fewer inquiries about keto diets
“In the world of athletics at least, meaning competitive athletes or serious recreational competitors, I’d say the keto phase has hit its tipping point,” Kleiner told NutraIngredients-USA.
“My barometer is how busy my practice is with people coming in asking about various things. It started years ago with the zone diet. They weren’t on that long. Initially they did quite well and then later not so much. And then they were on to the paleo diet. Then it was on to keto and they were getting on that bandwagon,” she said.
Proponents of the keto style of eating can sometimes engage in debates about which products truly deserve the title. The dieting philosophy calls for extreme restriction of carbohydrates to force the body to enter ketosis, or a state in which it is preferentially burning its fat reserves for fuel.
While there may be disagreements about whether some products using the word ‘keto’ on the label are truly helping consumers reach that goal, Kleiner said there is no disagreement about what the state is and how to measure it.
“There isn’t any argument in the scientific community about when you are in ketosis. It means your blood ketone levels have hit very specific values,” Kleiner said.
“The process of using fat instead of carbohydrate for fuel produces an incomplete oxidation and leaves ketone bodies left over. You have much higher levels of these when you use fat as your primary energy modality.
“You see the levels of acetone, acetoacetate and beta-hydroxybutyrate in the blood rise. Of these three we measure the last two and when the levels hit 3.6 and 4.7 in the blood stream respectively you are said to be in ketosis,” she said.
Diet might cut weight, but doesn’t support performance
While some consumers have reported promising weight loss results using the diet, Kleiner said it has not proven to be a winner for competitive athletes.
“You had athletes getting on that bandwagon. They would find that in the offseason they’d lose weight. Then they found that when they entered their competitive season they’d hit the wall and they’d end up in my office because some coach sent them,” she said.
Kleiner said that high intensity exercise and severe carbohydrate restriction just don’t mix. Athletes who have cut their carbs down to the 50 grams or so a day required to enter and maintain ketosis found that their perceived rate of exertion during workouts went up, but their actual power output declined.
“In some sports where power to weight ratio is important like cycling or distance running people would find an initial performance boost because they’re lighter, but that’s because their power hasn’t dropped off yet,” Kleiner said.
Kleiner said one that that is poorly understood in the general public about the ketogenic diet is that is does not necessarily mean higher levels of protein. While keeping to less than 50 grams of carbohydrate is difficult, adherents of the diet can’t fill in with more protein, Kleiner said.
“Your body wants carbohydrate. If you have too much protein your body will cleave off the nitrogen moiety that makes protein protein and use it as a substitute source of carbohydrate,” she said.
Keto diet as occasional tool
Kleiner said low carb eating styles may have a place in a periodization scheme. Periodizing diets is something she said she has advised her clients on for years, and brief spates of carbohydrate restriction could be a tool in that toolbox.
But Kleiner said in general, restrictive diets just cut out too many useful, important nutrition sources. The current baking craze has reawakened people to the basic physiological principle that eating the right kind of carbohydrates just makes you feel good.
“Americans have been eating too may carbs, and too many carbs from the wrong sources. But we know that a diet that is less than 40% carbohydrates can raise your risk of depression. People seem to have decided that a restrictive eating style in this time when our lives are already so restricted is just too much,” she said.
Keto star fades
As for the future, Kleiner said she thinks the keto star may be setting. In talking with her practicing nutritionist colleagues, she said its prevalence seemed already to be on the wane before the coronavirus crisis took hold.
“I’m not a soothsayer in this, but my sense is that coming out of the other side of this crisis that the keto side of the coin may not have as much promise as it once had for sports nutrition manufacturers,” Kleiner said.