If you haven’t heard of the keto diet by now, it’s probably safe to say that keeping up with the latest health trends isn’t really your thing. From wellness websites and doctor’s office magazines to the Twitter feeds of your favorite celebs, the diet has been everywhere in the past two years.
Though the jury is largely still out on the benefits of keto, it’s often touted as the answer to everyone’s weight loss prayers. But does the keto diet work for everyone? Unfortunately, nutrition experts say no. It can be restrictive, tough to sustain, and downright unhealthy for some people.
If you’re thinking of trying it, here’s what you need to know.
What is the keto diet?
The ketogenic diet was developed in the 1920s as a treatment for epilepsy, according to registered dietitian Lainey Younkin, owner of Lainey Younkin Nutrition. Now, Younkin says, it’s a fad diet based on putting your body into ketosis, a process of burning fat cells for energy.
Does keto work?
Proponents of keto say the low-carb, high-fat approach can lead to significant amounts of weight loss. “People do lose weight,” agrees Younkin. “But can they keep that weight off and can they follow keto long-term? For most people, the answer to those questions is no.” In other words, it’s not necessarily the kind of permanent lifestyle change you’re hoping to achieve.
Many health professionals worry about the extreme nature of the diet, which limits carbohydrates to less than 50 net grams per day and can often lead to nutritional deficits.
Who should try a keto diet?
So who is a good candidate for keto? It can serve a medical purpose for people with seizures. (For more information on the connection between epilepsy and keto, this 2019 review in Frontiers in Neuroscience breaks down much of the relevant research.)
According to registered dietitian Danielle Schaub, culinary and nutrition manager for Territory Foods, the diet can also help people who are looking to:
- improve or reset their insulin sensitivity;
- improve some health biomarkers, like blood pressure;
- or lose weight or body fat with a sedentary lifestyle.
Who shouldn’t try a keto diet?
On the flip side, there are several groups of people who should NOT do keto, per Schaub. They include:
- people looking to lose weight fast without having a plan on how to maintain the weight loss long-term;
- anyone with a poor relationship with food and/or disordered eating patterns;
- elite athletes;
- and anyone with pancreatitis, liver failure, kidney disorder, or other fat metabolism disorders;
- Diabetic patients who have ever been diagnosed with diabetic ketoacidosis.
Like with most restrictive diets, children and pregnant or breastfeeding women should also avoid keto unless otherwise instructed by their physicians.
Keto diet and diabetes
You may have noticed that people looking to improve their insulin sensitivity are often good candidates for the keto diet; typically, this refers to people who have diabetes, though not everyone with diabetes should try keto.
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“Patients with type 1 diabetes must be very careful with the keto diet because the ketosis process could increase their risk of diabetic ketoacidosis, a very dangerous state which can lead to hospitalization and death,” says Laila Tabatabai, MD, an endocrinologist at Houston Methodist.
Patients with type 2 diabetes, though, could benefit more readily from the keto diet. Dr. Tabatabai says that the reduction in carbs and overall weight loss on keto means your body requires less insulin, which in turn helps stabilize blood glucose levels.
But that still doesn’t mean you should start keto ASAP if you have type 2 diabetes. “Studies have shown that short-term use of the keto diet can help patients with type 2 diabetes lose weight [but we] do not yet have long-term data on its safety and efficacy,” emphasizes Dr. Tabatabai.
A 2019 review of the recent research into type 2 diabetes and low-carb diets published in Nutrients shows that most of the studies performed lasted several months (one, published in the American Journal of Clinical Nutrition, lasted 52 weeks). Though the results are positive in the short-term, all diabetes patients—whether type 1 or type 2—should talk to their doctors before starting the keto diet.
What to eat on keto
Eating keto means choosing foods that are low in carbs and high in fat…but that’s not always as easy as it sounds. Carbs aren’t just lurking in refined pastas and breads; many healthy foods, such as fruits and vegetables, contain carbs (along with dozens of necessary vitamins and minerals).
Here’s an example of some popular keto-friendly foods:
- Meat and poultry
- Dairy products like cheese, Greek yogurt, cottage cheese, and whipping cream
- Low-carb vegetables like spinach, cauliflower, and mushrooms
- Nut butter
- Bacon, jerky, and sausage
- Nuts, seeds, and monounsaturated oils
Because so many people are doing keto right now, there’s no shortage of recipes catering to the diet’s specifications—but eating keto still requires a lot of careful planning and preparation.
Not losing weight on keto?
As a reminder, the goal with keto is to put your body into a state of fat-burning ketosis by mostly eliminating carbs. Schaub says some people will reach ketosis after about one week, while others may take a little longer.
“Once you are in ketosis, if you are consuming fewer calories than you are expending, you will burn body fat and lose weight,” she explains.
However, it’s totally possible to be in a state of ketosis and not lose weight. Schaub says that if you enter ketosis but continue eating enough food to cover your energy needs, your body won’t start burning fat cells for energy because it simply isn’t necessary. You still need a calorie deficit to lose weight, ketosis or not.
There’s also another reason why you could find yourself not losing weight on keto or, worse, gaining weight: eating too many fatty foods. Since the keto diet is high in fat and fat is very calorie-dense, Schaub says you will gain weight if you are in an overall calorie excess regardless of where those calories come from. (In other words, keto is not a free pass to chow down on fast-food burgers all day.)
The bottom line: keto doesn’t work for everyone
Keto can work for some people, and there are benefits to being in ketosis even if you’re not dropping pounds; Schaub says it can improve insulin sensitivity and lower blood pressure. But there’s not a lot of research about keto yet to prove its claims. “We don’t know the effects of following keto long-term since most of the studies on the diet are short-term in the setting of treating epilepsy,” explains Younkin.
Meaning, diet wisely. Keto can be hard to stick with and most dietitians prefer that people adopt eating habits they can commit to long-term for optimal health benefits.