Jumping into high-fat, low-carb eating? Here’s what you need to know to sidestep challenges and set yourself up for success.
The ketogenic diet — a high-fat and very low carb eating plan — can be tough to start. After all, it’s likely a radical departure from the way you’re eating now (a typical standard American diet is high in carbohydrates and processed foods). But many people are trying the keto diet, which puts your body in a state of ketosis.
That’s what happens when your body’s carb-burning switch flips to a fat-burning one, a change that can influence everything from weight loss to type 2 diabetes — although scientists caution that much more research is needed on the health effects of keto diets in general. (1)
How do you make practical preparations in stocking your fridge and preparing mentally for the big change to come? Consider this your step-by-step guide.
In following a keto meal plan, you’ll be severely limiting carbs. Start off with between 20 and 30 grams (g) of carbohydrates per day, says the New York City–based dietitian Kristen Mancinelli, RD, author of The Ketogenic Diet: A Scientifically Proven Approach to Fast, Healthy Weight Loss.
Also make sure that you know what foods have mostly carbs, fat, and protein, so you can make the right choices. For instance, it’s not just bread, pasta, chips, cookies, candy, and ice cream that contain carbs. Beans may contain protein, but they’re also very high in carbohydrates. Fruit and veggies also mostly contain carbs. The only foods that don’t contain carbs are meat (protein) and pure fats like butter and olive oil.
“People are afraid of fat because they’ve been told that it’ll kill them,” says Mancinelli. What is confusing is that research today remains mixed. Some studies suggest that replacing saturated fat with polyunsaturated fat (and avoiding unhealthy trans fat) is important for mitigating heart disease risk, while others suggest that total fat and types of fat weren’t associated with cardiovascular problems. Deciding exactly how to eat then becomes confusing. What is helpful, the authors of one study noted, is to remember that food is more than a single nutrient, and it’s the overall quality of the diet that counts. (2) (They do say that high-fat, low-carb diets still need more research to assess their long-term health benefits and risks.)
To prepare for a high-fat diet, which can be uncomfortable at first, start making small adjustments to what you eat every day, she suggests, like ordering a burger on lettuce leaves and subbing green veggies for fries.
Instead of potatoes or rice with your meal, opt for a nonstarchy veggie. Start cooking with more oil, such as olive or avocado oil. Realize that old dieting habits — like making a plain skinless grilled chicken breast — just don’t make sense on a keto diet because you won’t get enough fat.
“Slowly start pushing out carbs and getting in fat. If you’re afraid of fat, a ketogenic diet won’t work for you,” she says.
One of the most common misconceptions about the keto diet is that you can eat as much protein as you’d like. But this is not a diet where you watch carbs only — you also have to keep your protein intake moderate, says Ginger Hultin, RDN, a Seattle-based registered dietitian. Protein can be converted into glucose, and therefore overeating protein can take your body out of ketosis. Think of your ratios as a small portion of meat topped with a generous amount of fat, rather than the other way around.
Look at a variety of keto websites and cookbooks for keto-approved recipes you’ll love. Mancinelli recommends finding four to five recipes with foods you know you’ll like. “That way you’re not standing around wondering what to eat, and turn to carbs,” she says.
Water is the top choice for keto dieters, thanks to the fact that it doesn’t contain any carbs and can keep keto-flu symptoms at bay. Here’s what else you’re allowed to sip.
Tell them your plan. You may not be able to eat what they’re eating during family mealtimes, so you'll want to prepare them (and yourself) for what your new habits will look like. Because this diet is often done only short term (three to six months), you can assure them that it’s temporary.
If you get pushback, announce: “I’ve done my research, I’ve figured out it’s safe, and I really want to try this,” recommends Mancinelli. They don’t have to like what you’re doing, but it does help if they have your back. A 2014 study found that having the support of friends and coworkers helped dieters more successfully lose weight and maintain that loss over a two-year period. (4) It also can’t hurt if everyone knows your goals on a keto diet so they’re less likely to push office treats or suggest splitting a side of fries when you’re out to dinner.
For all the attributes of a ketogenic diet (like weight loss), there’s one big side effect you have to be prepared for: the keto flu.
The keto flu is a term that refers to the period after you start the diet when your body is adjusting to burning fat for energy. “Some people have no problem with it and others are miserable,” says Mancinelli.
In the first week or 10 days, you may feel extremely lethargic in your limbs. Walking upstairs may feel impossible. You may deal with mental fog. Often, keto causes constipation, or potentially diarrhea, because of a change in fiber intake.
For that reason, you should pick a start date when your week isn’t crazy with deadlines and obligations; choose a slower time when you can rest as needed. Along the same lines, you’ll want to be sure to take it easy with exercise for the first week or two as your body adjusts to burning more fat rather than carbs for fuel.
In ketosis, Mancinelli explains, your kidneys excrete more water and electrolytes. Make sure you’re getting the sodium and potassium your body needs to function well. Salt your foods, drink salted bone broth, and eat nonstarchy veggies, such as asparagus, kale, bell peppers, and arugula.
Now that ketogenic diets have become popular, many keto hybrid diets have sprung up, including plant-based versions. (One is “ketotarian,” which is predominantly plant-based but includes the option of eggs, ghee, and fish and shellfish.) While this approach can be healthy, Hultin cautions against trying keto as a vegan. “Because you can’t eat beans or lentils on a ketogenic diet, and nuts and seeds are even limited due to their carbohydrate content, you’re really just left with some tofu and will need to rely on low-carb protein powder,” she says. There is a good possibility this won’t pan out. “I don’t see this as a sustainable diet due to the extreme restrictions,” she says.
In addition, there are medical conditions that should make you think twice about starting keto — or at least talk to your doctor before trying it out. Those include people on insulin, as well as those on oral and noninsulin injectable medications for high blood sugar or high blood pressure, says Hultin. Even struggling with GI issues may be a barrier to starting. “One of the side effects of a ketogenic diet is constipation, so if that’s a struggle, it’s a serious reason not to go on this relatively low-fiber diet,” says Hultin. Last consideration: If existing personal dietary restrictions require you to avoid foods like soy, eggs, nuts, dairy, or seafood, a ketogenic diet may be too limiting for you. Coming from a place of elimination in an already restrictive diet can make it incredibly tough to follow, she says.
A keto diet is not meant to be a forever diet, and experts recommend you keep it short-term. Mancinelli says that some people go on a keto diet a few times per year, while others will use it to lose weight and change their eating habits.
A whopping 46 percent of American adults still eat what’s considered a “poor” diet in American Heart Association standards, based on a survey of nearly 34,000 people. (5) For some people, going on a keto diet is an effort to change those poor habits, but there’s the risk of falling back into your old ways once the diet is over. If you go straight back to a standard American diet, you’ll likely lose any health benefits and regain the weight.
All this said, a serious caveat: There are some people who try to set themselves up to follow a keto diet long-term, but experts do not recommend that. A 2021 review of relevant studies advised against it, stating that while keto diets do have benefits for some people — they can, for example, reduce seizure frequency in those with drug-resistant epilepsy — most of the “positives” (such as a decrease in blood glucose) are either short-lived or equal to that of less controversial solutions. A keto diet can decrease body weight, for example, but so can many other dietary approaches. In the long-term, the risks outweigh the benefits, the researchers concluded. (6)
If you do decide to try a keto diet short-term, Mancinelli says that your ultimate goal should be “to shift your diet to a healthier pattern that involves eating less bread, less pasta, less flour, and less sugar,” as well as more nonstarchy veggies, she says.
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