6 signs you shouldn't do a keto or low-carb diet, according to a doctor

• The low-carb, high-fat keto diet has become popular for weight loss.
• Keto can be helpful for improving metabolic health, but it isn't for everyone.
• Avoid low-carb diets if you're stressed or seeking quick results, or have a history of disordered eating.

Keto diets have increased in popularity in recent years as people have turned to high-fat, low-carb eating plans to lose weight and improve their health.

There's evidence to support the keto diet as a tool for certain people to improve their health, but it isn't for everyone, according to Dr. Mark Cucuzzella, a professor at West Virginia University's School of Medicine who has published research on low-carb diets.

Here are six reasons you may want to think twice about starting or continuing a low-carb diet.

You're already metabolically healthy

Research suggests that a high percentage of Americans deal with some level of metabolic dysfunction. That includes people with obesity, insulin resistance, prediabetes, or Type 2 diabetes, which can happen regardless of weight.

If you are among the minority of people who have a healthy metabolism and good insulin response, then you don't have to worry about your carb intake. Good metabolic health means you don't struggle with some combination of issues with blood pressure, blood sugar, cholesterol, weight, or low energy.

"Just eat real food, whether that's low-carb or high-carb, and you'll be fine," Cucuzzella said.

You want to lose weight for short-term or aesthetic reasons

Low-carb diets can lead to weight loss, research suggests, since they can help to manage appetite and reduce sources of added calories such as sugar and refined grains.

But the primary benefit of keto is restoring metabolic health, improving insulin response, and reducing inflammation, Cucuzzella said.

"It's not about losing weight, it's about losing waist," he said. "We want people to keep muscle and lose visceral fat around the organs that causes inflammation. Losing inches off your waist means you're successfully using fat as fuel."

And while weight-loss diets work by restricting calories, Cucuzzella said that could backfire if you're doing keto for the first time, making it tougher to transition to burning fat for fuel if you aren't eating enough overall.

Finally, a significant amount of the quick weight loss that people can have on short-term keto diets is water, and those pounds can return when you reintroduce carbs into your diet.

You have a history of disordered eating

Low-carb diets can also be problematic if you have a difficult relationship with food, including current or previous disordered eating habits.

These include feelings of anxiety about gaining weight and a compulsive need to monitor or limit food, as well as binge eating, emotional eating, or addictive eating behaviors.

Any diet that restricts what you can eat can be extremely triggering for anyone with these or other forms of disordered eating, which experts say can be risky if left untreated.

It's best to seek professional support when considering a new diet.

You're under constant stress, sleeping poorly, or dealing with major life changes

It may be tempting to make a dramatic change during a tough time. But if you can't manage your stress, you're not getting enough sleep, or you recently had an upsetting life event, it's the worst time to change your diet, Cucuzzella said.

Those things increase your body's production of cortisol, the stress hormone, and too much can make it challenging to get the most out of a low-carb diet.

It's also best to be in the right state mentally and emotionally for a big dietary change so you can plan ahead and have plenty of support along the way.

"If you don't have the energy and time to prepare for success, you're not going to succeed," Cucuzzella said.

You experience low energy, moodiness, or other symptoms for more than a week

People on low-carb diets often experience a transition period where they may feel unusually tired or groggy, sometimes known as the keto flu.

Cucuzzella said that it's normal to feel a bit under the weather as your body adapts to burning fat but that you should start to feel more energized in four to seven days.

If you don't, that could be a sign that you have more significant metabolic issues that will take longer to resolve, or that something just isn't right.

Ongoing fatigue on a low-carb diet is a sign that you should take a step back and reconsider, ideally with professional help.

You're taking medication

Finally, while there's growing evidence that low-carb diets may help with chronic health issues like diabetes, it's important to consult an expert before trying one if you're already on medication.

Major changes to your diet can change how your body responds to medication, Cucuzzella said.

"You need to find a doctor that is very versed in metabolic health and will work with you to reverse the problem, not just manage it with more medications," Cucuzzella said.