Trying the Keto Diet? Watch Out for the 'Keto Flu'


FRIDAY, March 13, 2020 (HealthDay News) -- If you are feeling the aches and pains of what you think is the flu, a trendy diet may be the culprit instead, a new study confirms.

Researchers took a dive into what's become known as "keto flu" -- the fatigue, headache, nausea and mental fog that some people develop soon after starting a ketogenic diet.

The keto diet, which is loaded with fat and skimpy on carbs, has become a popular way to lose weight. By depriving the body of carbs -- its main source of fuel -- the diet pushes it to burn fat instead.

The tactic "undeniably works" in spurring quick weight loss, said Ginger Hultin, a Seattle-based registered dietitian and spokesperson for the Academy of Nutrition and Dietetics.

At the same time, though, it can leave people feeling miserable, at least in the first few weeks. That so-called keto flu has been recognized for some time, and it's thought to be the result of the radical dietary change. Keto plans typically recommend getting 70% to 80% of calories from fat, 10% to 20% from protein, and a mere 5% to 10% from carbs.

"You're asking your body to shift into a completely different metabolic state," Hultin explained.

For the new study, researchers looked to online forums to see what keto dieters had to say about their short-term side effects.

First, they found 43 forums with threads dedicated to "keto flu," then scanned posts from 300 users.

Overall, dieters' most common complaints were headache, "brain fog," constipation and other gastrointestinal problems. But their issues ran the gamut, from fatigue and dizziness, to heartbeat changes, sore throat and body aches.

People's symptoms generally peaked in the first week of starting the keto diet, then resolved over the next few weeks.

The findings, published March 13 in the journal Frontiers in Nutrition, do not necessarily reflect the typical keto diet experience -- or even the typical keto flu experience.

People who turn to online forums for help may be different from those who don't, said lead researcher Emmanuelle Bostock, of the Menzies Institute for Medical Research at the University of Tasmania, in Australia.

But, she said, there is still something to learn from their stories.

"It's important to consider symptoms from a number of perspectives in order to gain a composite picture," Bostock said.

For example, she said, the forum users give an idea of how severe and lasting keto flu symptoms can be: Of 60 people who discussed the extent of their symptoms, 45 described them as moderate or severe. And of 56 people who gave a time course, all but four said their symptoms faded within a month of starting the diet.

Hultin said that in the quest to find a diet, people may not always consider the unpleasant side effects. So it's important to be aware they exist.

But even if you battle your way through keto flu, is it a healthy way to lose weight?

"One of the biggest problems with our weight-loss culture is this endless diet rollercoaster," Hultin said. That is, people may shed pounds on the keto diet, or another restrictive plan; but if the diet is not sustainable, those pounds are likely to come back, and then some.

Despite the indulgence in fat, the keto diet is difficult to maintain, and severely limits carbs from healthy sources like vegetables, fruits, beans, whole grains and dairy. So there is a concern that dieters will fall short on various vitamins, minerals and fiber, according to Hultin.

Ultimately, she said, it's best to focus on cultivating a diet that supports your health, and can be sustained for the long haul. Actually enjoying your food is important, too, Hultin pointed out.

"A lot of times in my work," she said, "it's about helping people find a way of eating that's healthy and makes them happy."

As for the keto diet, Hultin recommended that people who have a chronic health condition, such as diabetes or high blood pressure, use caution. Talk to your doctor about whether it's a safe way to lose weight, she advised.

More information

The Academy of Nutrition and Dietetics has more on the ketogenic diet.

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