As another year ends, many of us promise to trade in our cookies and cocktails for salads and smoothies. And thanks to a surge in trendy eating plans, January is the official start of diet season for people looking to shed pounds in the new year.

It should come as no surprise that the most buzzed about diet of 2018 is continuing its momentum into 2019-yes, we’re talking about the keto diet. The extremely high-fat, low-carb eating plan has been touted for its ability to help you shed major kilos, boost your energy, and possibly even improve your health overall.

But does science actually support the hype surrounding keto? As with any restrictive diet, it may help you lose weight-but for how long? Before you start swearing off all those delicious carbs, here’s what to consider before you try the keto diet for weight loss.

Back up: What is the keto diet, again?

The ketogenic diet is a low-carbohydrate, high-fat diet designed to induce ketosis, a metabolic process whereby your body uses fat storage for energy instead of sugar, which is the body’s preferred energy source. Unlike other low-carb diets, which allow anywhere from 20 to 60 grams of carbohydrates a day, the recommended carb intake on the keto diet is less than 20 grams per day-that’s less than a single apple, banana, or sweet potato.

Another difference between keto and other low-carb diets is the percentage of kilojoules from protein. Sports dietitian Angie Asche says “a common misunderstanding is that keto is high in protein (like Atkins) but it actually limits you to no more than 20 percent of your total kilojoules from protein, to allow for over 70 percent to come from fat.”

The keto diet was originally introduced in the 1920s as a treatment for epilepsy, but it has gained mainstream popularity over the past few years. So why are people so obsessed with keto now? For one, keto is often seen as a quick fix for rapid weight loss-and a number of celebrities and social media personalities, such as Halle Berry (who seems to be ageing in reverse), have had success on the diet, says dietitian and diabetes educator Erin Palinkski-Wade.

“The fact that weight loss occurs on the keto diet, which includes foods that would traditionally be limited on diets, such as bacon and eggs covered with butter and cheese, doesn’t hurt either,” adds dietitian Christy Brissette.

Yes, the keto diet can help you lose weight-but you may gain it back

As with most diets that drastically reduce or eliminate certain food groups, the keto diet has been shown to aid in weight loss. This is likely due to the satiating effect of high-fat foods. When you feel full, you have less of an appetite and end up eating fewer kilojoules.

So yes, you may lose weight rapidly when you start the keto diet, but unless you follow the plan strictly and stay in a state of ketosis, gaining that weight back is very likely. The keto diet isn’t kilojoule-restricted, but the types of foods you can eat are significantly restricted, meaning you’ll probably have a hard time sticking to it for the long-term.

“While weight loss is shown to occur in short-term studies, the research is mixed on whether or not keto diets lead to greater fat losses when compared to higher carbohydrate diets,” Asche says. “Research also shows that while fat loss occurs, so does lean muscle mass loss,” since you’re consuming less protein than you normally would.

The keto diet may improve certain health conditions-but no more than any other weight loss diet

Researchers have also explored the keto diet’s effect on numerous health conditions, including diabetes and pre-diabetes, heart disease, Alzehimer’s disease, polycystic ovary syndrome (PCOS), and even acne.

“For those with diabetes, a ketogenic diet has been found to be beneficial in reducing insulin resistance and promoting improved blood glucose control,” says Palinksi-Wade.

Although there is research showing adherence to the keto diet for up to three years can improve heart disease risk factors, Brissette says “positive changes in these values happen with any weight loss diet, so it’s tough to say whether it’s the diet in particular or the weight loss that leads to these improvements. The research tells us the keto diet isn’t any better than other diets for improving these values.”

3 reasons to stay away from the keto diet

So if the keto diet may help you lose weight, or even improve certain health markers, why wouldn’t you do it? The answer is simple: It’s very restrictive, so it’s not ideal for long-term for weight loss.

It is not sustainable for most people

Palinski-Wade says she personally has clients who follow a keto diet and are successful, “but for the majority of people who go on this plan, I find they typically jump on board hoping for a quick fix and are unable to maintain the lifestyle long-term.”

Asche agrees that the diet is sustainable for some people long-term, but unless you are content with never eating carbs again, it’s just not realistic.

It can hurt your relationship with food

The keto diet can also impact your enjoyment of food and how you experience food-centric events, like family dinners, brunch with friends, or happy hour with coworkers. Because keto requires strict adherence that doesn’t allow wiggle room for occasional splurges, it can get in the way of enjoying everyday life.

This type of restriction might even make you a bit obsessive, “where you have to track every last gram, macro, never allowing yourself to ‘splurge’ on anything containing carbs or sugar in fear of knocking you out of ketosis,” says Asche.“Yes, it could promote weight loss, but there are several other methods to losing weight successfully that don’t involve restricting entire food groups, counting every last carbohydrate, counting your percentage of fat and protein intake daily, and being limited to meat, dairy, eggs, avocado, coconut, and low-carb vegetables.”

The side effects can be unpleasant

If the thought of missing out on your favorite carbs doesn’t bother you, the side effects of the keto diet may. Headaches, bad breath, and lack of energy (collectively referred to as keto flu) are common when people start the keto diet. Not to mention, you may experience constipation because your fibre intake plummets.

Brissette also warns that “the keto diet could also cause your body to use muscle for energy, which could slow down your metabolism and reduce your strength over time.”

The bottom line: The keto diet may help you lose weight at first, but it’s not sustainable for the average person and can greatly interfere with your daily life.

If losing weight is a major goal for you this year, consider exploring all of your options (preferably with your doctor and a dietitian) before you commit to a diet. There are many other eating plans for weight loss that are not as restrictive, are more sustainable, and have more research behind them.

Brissette recommends the Mediterranean diet (which was just named the best diet to try in 2019) as “one fantastic example of a way of eating that’s been tried and tested over many generations and has been consistently shown to promote longevity and reduce the risk of chronic disease.” The best part? It promotes a balanced plate of healthy, delicious foods-carbs included.

If you decide to give keto a try, it’s important to include plenty of minimally processed whole foods, such as low-carb vegetables, plant-based fats such as avocado, olive oil, and nuts, and lean proteins such as fish and poultry. As with any major dietary change, it’s best to follow it under the care of a dietitian or doctor.