If you want to pair a healthy vegetarian diet with the trendy ketogenic diet, is it possible? Find out how, plus see what the science says about this style of eating.

Brierley Horton, MS, RD

Eating a plant-based diet, or even going all-out vegetarian, can be quite healthy. Vegetarians tend to be slimmer, have fewer chronic conditions, and live longer than their meat-eating counterparts.

Pictured recipe: "Egg in a Hole" Peppers with Avocado Salsa

Then there's the ketogenic diet (that high-fat and ultra-low-carb way of eating), which conjures up images of bacon, burgers and butter. It can help you lose weight quickly, and it may help you improve your cholesterol and blood pressure, and manage your blood sugar levels (though the science to support these claims is limited).

Related: 3-Day Low-Carb Vegetarian Meal Plan

But can you combine these two "diets"? Put another way-is a low-carb vegetarian keto diet even feasible?

Vegetarian keto is doable. It'll require more brainpower and planning than the typical ketogenic diet, though, so we're going to walk you through what you can eat and then outline some common pitfalls and what to watch out for.

So what foods can you eat on a vegetarian keto diet?

This list of what to eat will get you started. Think lots of veggies-like the zoodles pictured above-with proteins and some fruit mixed in.

Plant-based fats: Avocado and its oil, coconut and its oil (steer clear of any sweetened coconut though), olives and their oil.

Low-carb vegetarian proteins: Tofu, seitan and even tempeh-because although it's higher in carbs than tofu and seitan, it's also high in fiber, so your net carbs make it keto-friendly. Be cautious of faux-meat burgers, bacon, etc., and read their ingredient lists and nutrition labels, as they may contain sugar or be an unexpected source of carbs.

Low-carb veggies: Of course there's cauliflower, but there's also zucchini, Swiss chard, mushrooms, asparagus, celery, spinach, bok choy, broccoli rabe, cabbage, broccoli, kale, Brussels sprouts and lettuces (arugula, green and red leaf, endive, romaine, etc.).

Nuts: All nuts are solid choices when you're eating vegetarian keto, but some are higher in fat and lower in carbohydrates than others, and those are pecans, macadamias, pilinuts and hazelnuts.

Seeds: You really can't go wrong here. Seeds are fatty, they're not that high in carbs, and they're typically full of fiber, bringing your net carbs down.

Dairy: Full-fat plain yogurt and plain cottage cheese (avoid flavored high-sugar varieties), hard cheeses, butter.

Eggs: This is arguably the easiest, healthiest and most complete way to get protein if you're eating vegetarian keto. Eggs also give you a nice dose of fat and have practically no carbs whatsoever.

Berries: Strawberries, raspberries and blackberries are all lower-carb fruit choices-not because they're actually low in carbohydrates, but because they're packed with fiber and so your net carbs are low. You'll probably want to skip blueberries, though-a cup will eat up nearly all of your daily carb allotment.

And, as important as it is to come up with a list of foods you can eat, to be successful on a vegetarian ketogenic diet, you might want to list the foods you can't eat too (i.e., those that will throw you out of ketosis stat). Those are: beans and lentils (aka legumes), grains, most fruits, and all varieties of potatoes.

Challenges with vegetarian keto

The main reason why a vegetarian keto diet is so challenging is because many of the staples of a vegetarian diet are incredibly high in carbs, particularly foods like beans, lentils and whole grains that vegetarians rely on for protein, but are also packed with carbs.

Another speed bump is that vegetarians already need to be mindful of falling short on key nutrients, such as vitamins B12 and D, iron, zinc, calcium, omega-3s and even protein. Layer on another restrictive diet like keto and it can be that much harder, because cutting out breakfast cereal (fortified with B12), legumes and whole grains (for zinc, iron and protein) limits key sources of some of these nutrients.

As with any ketogenic diet, there may be unpleasant (and unhealthy) side effects like constipation, bad breath and keto flu (learn more about surprising side effects of eating keto).

What does the science say?

Search a scientific research database for "vegetarian keto" and you won't find much. You're pretty much limited to studies of pregnant women with chronic kidney disease who are put on a vegetarian-keto-like diet (in reality, it's a specific low-protein diet) in an effort to carry their babies as close to full term as possible.

There are a couple of studies, though, that look at low-carb diets and break out whether the protein and fat comes predominantly from animal- or plant-based sources. Both studies (neither of which is very recent) found that eating low carb and getting most of your fat and protein from plant foods was healthier. (The study in women showed it could lower their risk of heart disease, and the study in men showed it could lower their risk of type 2 diabetes.) But while these diets were low in carbohydrates, they weren't fully keto.

Bottom line

If you're a carb-loving vegetarian, trying out vegetarian keto could curb your tendency to overdo it in the carb department and help you diversify your diet. But this is a way of eating that requires some up-front planning and due diligence along the way so you don't become nutritionally deficient. And, ultimately, it's best as a short-term diet, not one to stick to for the long haul.

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