By now, you’ve heard a ton of buzz about the ketogenic diet. This high-fat, low-carb eating plan is popular, but can also be extremely divisive. Your coworker says he lost XX pounds — and eats all the bacon he wants. Your neighbor, on the other hand, said she felt so tired and stopped the diet after four days. If you’re thinking of trying keto yourself, you’ll best set yourself up for success by knowing — and preparing for — what lies ahead.
YOU’LL ENTER KETOSIS QUICKLY
The goal of the keto diet (which encourages eating high-fat, moderate protein and is very low-carb) is for your body to enter ketosis, or a state where it burns fat for fuel, rather than carbs, the normal source of energy. Expect to be in ketosis 24–48 hours after starting the diet, depending on your carb intake, says Scott Keatley, RDN, of Keatley Medical Nutrition Therapy in New York City.
Some people have the wrong impression about keto, assuming it’s a diet where you just avoid grains and sugar. In reality, you also have to forgo legumes, fruit, starchy vegetables and most dairy in order to hit those super low-carb targets. Considering it’s so easy to eclipse the 20–50 gram daily carb limit (for instance 1 cup of blueberries has more than 20 grams), you have to make sure you’re tracking your carbs very carefully. That means things like counting every baby carrot every step of the way.
YOU MAY FEEL AWFUL AT THE START
For all the stories you may hear about people feeling better than ever on keto, you may not expect what happens to so many in the beginning: the keto flu. “The keto flu is less of an illness and more of a feeling of lethargy,” says Keatley. Your body prefers to source its energy from carbohydrates, he notes. When it makes the transition to being a fat-burner, “your body is unable to supply the energy you need as quickly,” he adds. Expect this not-great feeling to stick around for a week or less until you adjust. Keatley advises adjusting your diet gradually (decrease carb intake while upping fat) to make the transition smoother.
YOU’LL HAVE TO ADJUST YOUR WORKOUTS
Remember how we said your body loves to run on carbs? Keto may have a negative effect on your gym sessions if your muscles don’t get the fuel they need. “Some research has had mixed results when it comes to endurance and strength on the keto diet, so it’s hard to know for sure if your workout will be impaired or improved on keto,” says Abbey Sharp, registered dietitian and author of “The Mindful Glow Cookbook.” “My experience tells me most people thrive exercising with some quality energy from carbs, so until your body is a pro at running on fats, it will likely be a tricky transition,” she says. One study in the journal Metabolism concluded that after 12 weeks of keto adaptation, endurance athletes lost more weight and body fat compared to a high-carb group without impacting their performance. However, the study also found the athletes said their energy dropped for the first 7–10 days, and then their performance suffered for 4–6 weeks. It concludes that if you’re an athlete going keto, you should time it right and avoid starting the diet 4–6 weeks before an event.
YOUR GUT MAY BE OFF
Most Americans don’t get enough fiber to start with — and that’s before cutting out fiber-rich foods like beans, whole grains, fruits and veggies, as is necessary on keto. During the diet, where the focus is on meat and fats, which don’t contain fiber, it’s easy to miss out on the digestion-friendly nutrient. “Cutting down on these sources of fiber can lead to difficulty ‘going,’” says Keatley. No matter your diet, your goal should be about 25 and 38 grams of fiber daily for women and men, respectively. If you do get stopped up with constipation, Sharp recommends increasing your consumption of high-fiber vegetables (like avocado, broccoli and greens), drinking more water and upping your activity level.
YOU PROBABLY WON’T REACT TO KETO LIKE YOUR CO-WORKER
Or anyone else, for that matter …
While someone may say they’ve never felt better and can think clearly, you may find the exact opposite. “Keto fans often suggest they feel and think better on keto, while others tell me they couldn’t get anything accomplished in the day because they felt in a fog, even after months of trying the diet,” says Sharp. Check in with yourself often and adjust where necessary. Consider working with a registered dietitian, who can help you plan a diet to feel your best, before embarking on keto. It’s also worth mentioning that what you eat is supposed to make you feel great; if keto makes every day a slog to get through and you’re miserable, it may not be right for you. (And, hey, that’s OK.)
YOU NEED TO DRINK UP
Keep a water bottle by your side and sip often throughout the day. On keto, kidneys excrete more electrolytes and water, so it’s easy to get dehydrated, says Sharp. For the same reason, make sure to salt your food to get the sodium you need.
YOU MAY WANT TO EAT A TON
When you hear the word diet, you assume you’re going to go around hungry. And while keto is restrictive, it is made up of mostly fat. “Fat is very satiating, so many people are surprised at how full they are,” says Sharp. Many people find it tough to eat enough fat throughout the day, she adds, so it might take some work to get your daily intake perfect. Fair warning.