The backbone of a keto plan is its extraordinarily high fat content, making up 65 to 80 percent of calories daily. Protein—which can raise blood glucose, though not as much as carbohydrate does—makes up 15 to 25 percent of calories on the keto diet. And carbs are even more heavily restricted to just 5 to 15 percent of calories. That’s only about 20 to 50 grams a day (compared with the average 245 grams daily), or the amount in a small apple or a cup of cooked brown rice, respectively.
“If someone with diabetes is [taking insulin or oral type 2 meds in the sulfonylurea or meglitinide class and is] following this diet, they need to know that their blood sugar can drop really quickly, so it’s critical that they check it more frequently,” says Toby Smithson, MS, RDN, CDE, author of Diabetes Meal Planning & Nutrition for Dummies. “Don’t wait for it to happen. Meet with your doctor or diabetes educator in advance so that you can troubleshoot exactly what to do if your blood sugar drops.” If it’s an infrequent occurrence, you may be advised to treat with fast-acting glucose. But frequent lows may require medication adjustments or the addition of more carbs to your eating plan.
The idea that ketosis is human beings’ natural state is also contradicted by the heavy dependence of human embryonic and fetal development on glucose. All women become insulin resistant during normal pregnancy as glucose is directed toward the developing baby. Pregnant women deprived of carbohydrates are at high risk of developing ketoacidosis in later pregnancy. This dangerous condition can occur as the nutrient needs of the developing fetus reach their peak and drive up maternal ketone production.
What about fruits and vegetables? All fruits are rich in carbs, but you can have certain fruits (usually berries) in small portions. Vegetables (also rich in carbs) are restricted to leafy greens (such as kale, Swiss chard, spinach), cauliflower, broccoli, Brussels sprouts, asparagus, bell peppers, onions, garlic, mushrooms, cucumber, celery, and summer squashes. A cup of chopped broccoli has about six carbs.
A keto diet has shown to improve triglyceride levels and cholesterol levels most associated with arterial buildup. More specifically low-carb, high-fat diets show a dramatic increase in HDL and decrease in LDL particle concentration compared to low-fat diets.3A study in the long-term effects of a ketogenic diet shows a significant reduction in cholesterol levels, body weight, and blood glucose. Read more on keto and cholesterol >
In terms of weight loss, you may be interested in trying the ketogenic diet because you’ve heard that it can make a big impact right away. And that’s true. “Ketogenic diets will cause you to lose weight within the first week,” says Mattinson. She explains that your body will first use up all of its glycogen stores (the storage form of carbohydrate). With depleted glycogen, you’ll drop water weight. While it can be motivating to see the number on the scale go down (often dramatically), do keep in mind that most of this is water loss initially.
Cost. At the grocery store, your shopping cart can take on a whole new look (and price tag) thanks to high-ticket items such as beef, fish, poultry, pork, and cheese, which are replacing budget-friendly pasta, potatoes, rice, and bread. And chronic constipation may require fiber supplements or stool softeners. Before beginning a keto diet, determine whether it’ll fit within your budget.
Con: Results can vary depending on how much fluid you drink. By drinking more water, you dilute the concentration of ketones in the urine and thus a lower level of ketones will be detected on the strips. The strips don’t show a precise ketone level. Finally, and most importantly, as you become increasingly keto-adapted and your body reabsorbs ketones from the urine, urine strips may become unreliable, even if you’re in ketosis.