Waffling between trying out intermittent fasting or the ketogenic diet? First of all, put down the waffle, because they aren't on the menu for either of these popular diets. Sorry. But now that we've got your attention, let's get down to business. The ketogenic diet [1] and intermittent fasting [2] have pretty much taken over our collective news feeds at this point, and for good reason. They've both been touted for their ability to help people drop weight without restricting calories, improving blood sugar, cholesterol, and blood pressure numbers.

The perks sound similar, but these diets differ in how they work and who should be using them. We're breaking down the ins and outs of both diets, as well as how to determine if either of these may be right for you.

What Is the Ketogenic Diet?

The ketogenic diet, or keto, is all about getting your body into the fat-burning state of ketosis [3]. Basically, by shifting your calorie intake to high-fat, moderate-protein, and very low-carb, your body stops burning glucose for energy and begins burning ketones. This allows your body to turn to stored fat for fuel instead of the sugar in your morning bowl of Froot Loops.

The benefits of being in ketosis, according to Jimmy Moore [4] (he literally wrote the book on keto [5]) include better sleep, stable blood sugar, reduced inflammation, improved blood pressure and cholesterol, clearer memory and cognitive function, better recovery from exercise, and maybe even clearer skin.

How Does the Ketogenic Diet Work?

When we say low-carb, we mean low-carb. If you go this route, you'll be forgoing bread and pasta and replacing them with high-fat foods like avocado, beef, coconut oil, and cheese. It's not all burgers and bacon, though. You'll also be loading your plate with lots of low-starch veggies like greens, tomatoes, onions, broccoli, and peppers. Don't worry — there are tons of keto recipes [6] out there for you to try, including dessert [7].

A typical day might start with eggs, bacon, avocado, and sauteed spinach. Lunch could include a big green salad with chopped tomato, hard boiled egg, crumbled bacon, and an oil and vinegar dressing. For dinner [8], roasted salmon and broccoli make for a simple keto dish. Oh, and don't forget the butter coffee [9]!

Who Should Try the Ketogenic Diet?

The keto diet is not for the faint of heart. It takes planning, preparation, and major dedication. But if you have a lot of weight to lose or your doctor has urged you to improve your health, many people feel this is the way to go. When it comes to keto, it's not just about being low-carb; proponents claim that you need to enter (and stay in) ketosis to reap the full benefits. The only way to know if you are in ketosis is to test your ketone levels on a daily basis. You can use a blood meter (Moore has developed his own [10] low-cost version), a breath meter [11], or you can test your urine. Of these three, testing for blood ketones is the most accurate.

Moore also told POPSUGAR that if you get out of ketosis (by taking in too many carbs), "It's a lot harder to get back into ketosis without fighting hunger, cravings, and other side effects of not being primarily fuelled by fat and ketones." Basically, you have to be super committed to keto in order to make it work, and that approach doesn't work for everybody. If you don't like following rules or you aren't a planner, keto may not be for you.

Some registered dietitians downright don't recommend keto [12] and warn it could be dangerous, especially for anyone who has a pre-existing health condition. According to Dr. Josh Axe [13], "The keto diet can be dangerous for people with diabetes or kidney disease. It is always best to work with your doctor to determine if this is something that will work for your body and lifestyle."

What Is Intermittent Fasting?

Intermittent fasting [14] is much different than keto, but offers many of the same benefits (and the transformations [15] are pretty amazing). There are multiple ways to approach IF, but it always involves some level of shortening your daily eating window so that your body is not constantly pulling energy from the food you are taking in, forced to utilise fat stores for energy. Most people do this by not eating after a certain time in the evening (say, 8 p.m.) and then skipping breakfast the following morning.

Dr. Anthony Gustin [16] told POPSUGAR that IF can deliver "effortless fat loss, blood sugar regulation, higher metabolism, and decreased inflammation." Sounds good to us, but what can you eat?

How Does Intermittent Fasting Work?

With intermittent fasting, it isn't so much about what you eat, but when. People love IF because you don't have to count calories or weigh and measure your food. By simply sticking to your eating window, it just seems to work [17], though it's important to remember that the quality of the food you eat will have an impact. Bingeing on junk food during your eating window will not be as beneficial as eating lots of protein and greens.

While you can tailor IF to fit your schedule, a typical day would start with water or black coffee. That means no breakfast. Around noon, you finally get to break your fast with a big, protein-packed salad and maybe some fruit. In the afternoon, you may snack on some fruit and nuts, a smoothie, or another healthy snack [18]. For dinner, you'll want to have a big meal like these stuffed sweet potatoes [19], because you won't be eating again until midday the following day.

Who Should Try Intermittent Fasting?

If you are tired of counting calories and battling sugar cravings, intermittent fasting may work well for you. It isn't as strict as keto, but you do have to stick closely to your eating window to see results. What's nice about IF is that there is more than one way to make it work [20], so you can always adjust as necessary.

Just as with keto, if you have any pre-existing health conditions, you definitely want to get the green light from your doctor before proceeding with any dietary changes. Dr. Axe warns that, "If you suffer from low blood sugar, going for an extended period of time without food can lead to a dangerous drop in blood sugar, resulting in hypoglycemia symptoms like shakiness, headaches, and fatigue. It can also be dangerous for those with a history of eating disorders, as IF may encourage unhealthy behaviours and trigger symptoms." Dr. Gustin adds that, "People with pre-existing hormonal conditions or missing a gallbladder should skip on both IF and keto as nutritional therapies."

Stefani Ruper [21], who has written extensively on the topic of intermittent fasting, also warns that women who are trying to conceive, are currently pregnant [22], or are breastfeeding, should hold off on IF. "If you notice any negative changes in your mood, energy, sleep, menstrual cycle, libido, or skin, or if you find yourself having obsessive thoughts about food, IF might not be working for you," she added.

And, the final question . . .

Can Intermittent Fasting and Keto Work Together?

Dr. Gustin says, "Intermittent fasting and ketosis work wonderfully together. Intermittent fasting helps raise levels of ketones by keeping insulin low, and being in ketosis while intermittent fasting allows you to burn fat for fuel and decrease appetite." Dr. Axe agrees, saying, "It is actually ideal to do intermittent fasting in tandem with the ketogenic diet. When it comes to fasting, an advantage of the keto diet is that it can help to decrease hunger and cravings, make it easier to comfortably go longer periods without eating." So, if you really want to go all in, it looks like IF and keto [23] actually work really well when done at the same time.

With 2018 New Year's resolutions closing in quickly, are you up for the challenge?