- The low-carb, high-fat keto diet has become popular for weight loss.
- Keto can be helpful for improving metabolic health, but isn't for everyone.
- Avoid low carb diets if you're stressed, seeking a quick fix, or have a history of disordered eating.
- Visit Insider's homepage for more stories.
Keto diets have skyrocketed 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 School of Medicine who has published research on low-carb diets.
Here are six reasons why you may want to think twice about starting or continuing a low carb diet.
You're already metabolically healthy
Around 88% percent of Americans currently deal with some level of metabolic dysfunction, according to research. That includes people with obesity, but also 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 shows, since they help 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, according to Cucuzzella.
"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 can 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 people have on short-term keto diets is water, and those pounds will quickly return as soon as 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, but also binge eating, emotional eating, or addictive behavior toward certain foods.
Any diet that restricts what you can and can't eat can be extremely triggering for anyone with these issues, as well as other forms of disordered eating, which can be risky if left untreated, according to experts.
If this is you, it's always best to seek professional support before 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 currently 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.
All of those factors increase your body's production of cortisol, the stress hormone, too much of which 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 it's normal to feel a bit under the weather as your body adapts to burning fat. However, 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.
Either way, 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 research that low carb diets may help address chronic health issues like diabetes, it's important to consult an expert before trying one if you're already on medication.
That's because major changes to your diet can potentially 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.